CLIMBING GEAR CLIMBING BELT Climbing is arguably the most dangerous activity you will ever engage in. It is probably more dangerous, statistically, than driving your car. The most common home accident is falling off a ladder. However, if you have the right equipment, climbing your tower will be much safer than climbing the familiar ladder because you will be hooked in to your tower 100% of the time. The safest, most comfortable, and most versatile type of climbing belt is a seat harness type that has the following features: 1. Positioning D-rings. One at each hip, for use with a positioning lanyard that goes around or through the tower, that is rigged once you reach your work position. 2. A suspension D-ring ring, in the center, just above your navel, for your "cowtails", a V-shaped, double ended climbing/suspension lanyard that you use to hook yourself in while you climb, or when you hook to a single place such as a mast or climbing rope. 3. If you are a professional tower climber, you will need to follow OSHA requirements for your harness. In this case, you will have to have a "fall arrest' type harness, typically having a full body arrangement and a specific, fall-arrest ring between your shoulder blades. 4. Wide straps around your legs and under your seat, that let you sit and take the weight off of your feet. Loads on the center D-ring from suspending, or short falls, are not applied to your lower back. 5. A belt around your waist having accessory loops for tool buckets and carabiners. It's great to have one for tools, another for parts, and another for snacks and/or drinks (a break in the middle of a work session works wonders!). 6. Lightweight. Most are made of nylon and already are. Stay away from leather belts which are no longer approved by OSHA. The leather can dry out and become seriously weakened without appearing to be. 7. Easy to get into and out of, and comfortable to wear for long periods. 8. Cost. Can you place a cost on your life? Medical bills? Permanent disability? For God's sake don't fool around with ordinary garment belts and dog leash chains! A harness with the above features can be had (in 1998) for between $100 and $200, the best insurance you will ever buy! Isn't that cheap, in the grand scheme of things? You will **feel** safer on the tower, and more at ease, allowing you to concentrate on your work, making you even safer. The best harness I have seen for this purpose is a cross between the mountaineering/caving style and the industrial work positioning style. It is the Navaho Vario, part #C79, made by Petzl. See Petzl on the web at http://petzl.com and their technical reference page at http://www.petzl.com/FRENG/toc.html. You will have to download their work/rescue catalog supplement in PDF format from http://www.petzl.com/work/work.html to see the description of this versatile harness. This harness gives you a tremendous degree of freedom since it has no shoulder straps to confine your upper body and chafe your neck. It is also one of the easiest to put on. Some tower climbers are switching to the OSHA-approved, full fall arrest harness with positioning belt D-rings, such as the model #3520 by DBI/SALA. It has the positioning rings at the hips, a chest ring for suspension, and a fall arrest ring in the back. You have all sorts of options here. It's safer than the simple old lineman's belt because you have a second, fall arrest lanyard that is attached to the tower in addition to your positioning lanyard. However, with this design, the fall arrest D-ring is on the back, between your shoulder blades, and the fall arrest lanyard is longer and less convenient to work with. If you do fall, you won't go far, but you will be jerked around more violently than the shorter cowtails arrangement that connects in the front. SOME THOUGHTS ABOUT FALL ARREST Again, for industrial/professional use, you will need an industrial "fall arrest' rated harness to comply with OSHA (Occupational Safety and Health Association)regulations. Amateurs maintaining their own towers do not have to be OSHA compliant. This is an example of an industrial requirement that, although it may save your life, still only comes in to play *after* you have begun to fall, and may still leave you with injuries. There are many different types of harnesses available for different applications. Although harnesses designed for mountain climbing, caving, rescue and industrial suspended work are not specifically designed for tower climbing, and may or may not be OSHA approved, they are also, nonetheless, designed to protect the wearer's life and, wherever possible, to *prevent* a fall from occurring. Your climbing methods and equipment should be tailored to prevent a fall in the first place. The ultimate decision is up to you, to determine which product keeps you the safest, and how much risk you are willing to take when climbing. Again, in all matters, *you* are the one who is the most in control of your own safety. A complete understanding of the risks you take and the solutions available to you is the best tool at your disposal. CLIMBING LANYARDS OK, now that you have a good harness, on to lanyards. Here are the three most useful types: 1. A cowtails lanyard, attached in the front, with two, 20-30" tails and two hooks, that you use to hook yourself in 100% of the time you are above the ground. Imagine the shape of the letter "V": the bottom vertex of the "V" connects to your front suspension ring, and the two free ends connect to whatever you are suspended from. This lanyard is similar to the one used by rock climbers, mountaineers, and cavers, where the term originated, except that both legs are the same length. Typically you would make your own from a good quality, `dynamic' (stretching) climbing rope, and use 3, readily available, locking carabiners for the attachment points, tied on using figure-eight knots. When you use this lanyard properly, alternating the hook points in a leapfrog method as you move up or down, you can't fall more than a few inches if you slip or lose your grip, limiting the shock and injury potential to a minimum. 2. A fall arrest lanyard, attached in the back, having a single, 36-72" line and hook that is designed to slowly break your fall. Typically, it is constructed with fan-folded, stitched web that rips open in a controlled way to absorb the energy of your fall as it pulls tight. Obviously, its shock absorption capability is destroyed by any fall and must be replaced. These cannot be homebrewed, are harder to find, but are available commercially. If you lose your grip you will fall far enough to develop enough momentum for a serious jerk! Since the fall arrest ring in a full body harness is behind your back, you will be pitched forward into the tower, putting you at risk for a head injury if you are not also wearing a helment. If you use this method, you must keep your fall arrest lanyard clipped as far overhead as possible to minimize your fall. 3. A positioning lanyard. This is a single line, 30-40" long, fixed or adjustable, having a hook at each end. The positioning lanyard goes around or through the object you are climbing and clips on to the D- rings at your hips to steady your torso while you are working. This is the lanyard most people are familiar with, the strap that linemen and loggers use to place around a pole or tree. These are readily available commercially, but are most easily homebrewed with a length of `static' (non-stretching) climbing rope and carabiners, tied on using figure- eight knots. You can make more than one with different lengths inexpensively, for use with different size towers. CARABINERS Carabiners are the handiest devices for climbers. They are sort like an oversized, oval-shaped single link of chain, where one side of the link is hinged to allow it to open and form a hook, and then snap closed again. The swinging portion is called the gate. Carabiners come in a variety of shapes, and fall into two basic classes: locking and non-locking. The locking variety use a small threaded, or spring loaded ferrule that screws over the joint in the gate to prevent it from opening if the carabiner is pressed against another object. You should always use the locking type carabiners for your personal safety lanyards. One particularly fast type of locking carabiner uses a spring-loaded ferrule that releases the gate only after a quarter-turn twist. This type can be opened very quickly with a simple, but deft move of the fingers of one hand to both rotate the ferrule, and press the gate open in the same movement, yet remain immune to accidental openings after locking. This type is called the auto-locking carabiner, and is particularly well suited to personal lanyards. My favorite auto-locking carabiner, which uses the above twist-locking scheme, is the HMS Munter Auto-lock by Omega (available from Rock `n' Rescue). Non-locking carabiners are handy for hooking ropes, loads, and gear together. They're faster and far more trustworthy than a hasty knot tied by an inexperienced person on your ground crew. Miniature carabiners are also handy only for hooking small tools to your harness for work up the tower. CLIMBING SAFELY WITH HARNESS AND LANYARDS Again, your climbing method should be tailored to prevent a fall in the first place, whenever possible. When you work on your tower, you need a combination of two lanyards: the cowtails or fall arrest lanyard to keep you hooked in while climbing, and the positioning lanyard. Don't be tempted to use a positioning lanyard by itself and simply drag it up the tower as you climb. Although it is safer than free climbing, if you lose your grip or foothold, you can still slide all the way down to the next antenna, guy attachment point, or the ground, whichever comes first, gathering momentum and most likely injuring yourself as you try to grab back onto the tower. Even worse yet, DO NOT FREE CLIMB if you can possibly avoid it! It's fast and very tempting. As far as climbing a tower goes, when you climb with no safety equipment attached to the tower, it is known as "free climbing". In the workplace, it is illegal per OSHA rules to free climb and you're supposed to be attached to the tower 100% of the time. Since people working on their own towers or anyone doing tower work for free are not subject to OSHA rules, your own method is up to you. Don't take unnecessary risks! Imagine having a dizzy spell or muscle cramp coming down a tower - you want to be attached at all times. Although climbing with lanyards is much slower, you are **so** much safer. If you are in a hurry, then you shouldn't climb anyway. It's a compromise you can live with. When you climb up with a fall arrest lanyard, start by hooking it above you. Climb up above the hook, stop, reach down, unhook the lanyard, re- hook it above you, and repeat. Notice that you are hooked most of the time but not while you are repositioning the hook. If you slip at this point, you are gone. To stay connected to the tower 100% of the time, you have to thread another lanyard, such as your your positioning lanyard, around the tower while you reposition the fall arrest lanyard. Pretty slow, but you stay 100% connected. When you need a rest, you must hold on with one arm while you set your positioning lanyard around or through the tower, and hook it before you can lean back and fully rest. However, if your fall arrest harness is not too long, you could possibly climb down or bend your knees to transfer your weight to the lanyard, and "hang" in your harness to rest. This isn't always too comfortable. When you climb using cowtails, start by hooking one tail above you. Climb up above the first tail, hook the second tail above you, reach down, unhook the first tail, and repeat. Notice now that you are hooked **100%** of the time, even while you are repositioning each hook. When you need a rest, simply bend your knees to transfer your weight to the upper tail and you can "sit" quite comfortably to rest at a moment's notice! When you get where you're going on the tower, you can clip both tails at the same brace and remain partially suspended while you work. If your cowtails are just the right length, your weight will divide between your feet and the lanyards. Notice here, that since the lanyards are already taught, and your feet are placed, you *cannot* fall at all. This is fall prevention at its best. Then, of course, you still have your positioning lanyard, which you carry up with you, and you can connect this to your side rings for the ultimate stability. CARRYING TOOLS You can purchase or make pouches for carrying tools and parts with you up the tower. This keeps your hands free for climbing at all times. A pouch fixed to your harness is handy enough, but you still have to reach around your side to retrieve the tools or parts. See the sources section for places to purchase these. For convenience, you can remove the pouch from your harness and clip it to the tower adjacent your your work area, to keep things ready at hand. HOMEBREW TOOL AND PART POUCHES You can make a nice tool pouch that is especially well suited to tower work with a minor adaptation of readily available tool pouches. In my case, I purchased a 10-pocket, suede tool pouch from Wal-Mart. Cut a piece of 1/2" diameter wooden dowel to the same length as the belt loop in the pouch. Insert the dowel through the belt loop right at the top and secure this in two places by driving short tacks through the loop from the back side into the dowel. Next, pinch the loop tight around the dowel and cut a vertical slit in the leather just below the dowel, at the balance point. Attach an oval carabiner at this point and orient it such that it hooks through the pouch, around and under the dowel, and the gate faces away from the front of the pouch. Now, you can easily clip this pouch onto your harness as you climb, then remove it and clip it to a horizontal tower brace right at your work position. Since the back side of the pouch is flat, it fits very nicely at your side or on the face of the tower. Make a second one for parts. ROPES & KNOTS The venerable bowline has, heretofore, probably been the most widely used knot for forming a loop. However, the figure-eight knot is now gaining more general acceptance as the knot of choice for those who trust their lives to rope in fire, rescue, and recreational climbing activities. The figure- eight knot is easier for most people to tie, has a larger bend-radius (stronger), is more resistant to self-untying, and yet is easier to untie than the bowline after strain-tightening. Use the figure-eight to tie ropes off to objects, form loops in the ends of ropes, attach carabiners, or for a stopper knot on the free end of a rope. Along with the figure-eight, the prussic knot is also indispensable. It is related to the taut-line hitch and has a remarkable capacity to grab onto a vertical rope, pipe or mast without slipping. The knot will not slip when tension is applied to the free loop, yet it can be slid back and forth easily by pushing directly on the knot itself. A prussic loop is a 12-18" diameter loop of smaller, 6mm cord, formed by tying the ends of a single piece (around 48" long) together using fisherman's knots, forming a simple rope ring. Make up several prussic loops and keep them on hand. Grab a loop and tie it around the rope or pipe or mast you want to lock onto, for the prussic knot, and use the resulting short loop as an attachment point for your carabiner. This technique is extremely useful, for instance, to set a pulley on your mast to use for tramming an antenna or other hauling purposes, where there are no braces to hook a carabiner. You can also use the prussic to anchor your cowstail or fall arrest lanyard. Here are a couple of excellent places on the web to learn how to tie these useful knots and more: The Cave Training Manual: http://www.nottingham.ac.uk/~styms1l/cave/ The Roper's Knots Page: http://huizen2.dds.nl/~erpprs/kne/kroot.htm Two good places to purchase harnesses, ropes, carabiners, and other climbing gear: REI outdoors http://www.rei.com http://www.rei-outlet.com Inner Mountain Outfitters http://www.caves.org/imo/default.htm Rock `n Rescue http://www.rocknrescue.com/default.htm MAKING YOUR OWN LANYARDS COWTAILS LANYARD Obtain a 115 inch long piece of 10.5mm dynamic climbing rope. That seems like too much rope, but figure-eight knots use quite a lot of rope. It's possible to use a non-stretching rope, but the dynamic type will produce less shock if you fall. The figure-eight knots will also absorb shock as they tighten during a fall. Fold the rope in half and tie a figure-eight knot in the center, forming a small eye loop for your center carabiner. This is the vertex loop that attaches to your center suspension ring on your harness. Attach a locking-type carabiner to the vertex loop (a screw- locking type is best here, since you won't be opening it often). Now tie figure-eight loops in each end, for the climbing hooks. You should leave about 3-4 inches of excess in the loose end of the knot for now. Attach auto-locking carabiners to these end loops. Now put on your harness and take the cowtails lanyard over to your tower. Hook the vertex on to your suspension ring, and hook one tail to a tower rung. Climb up a little and hook the remaining tail as high as it will go, which will put the tail ends around 4 feet apart. Adjust the tail end knots such that the two tail carabiners reach their nearest tower rungs easily without much slack. Don't make them too long, or you will have to bend down too far to reach the lower tail when climbing. You must be able to reach the lower end easily after setting the upper. After you are satisfied with the lengths, tape the loose ends from the knots to the main rope for neatness and an extra measure of security that the knot will not come undone. POSITIONING LANYARD This plan will make a lanyard that is just right for Rohn 25 tower. For Rohn 45, add about 8 inches to the raw length measurements. Obtain a 90" piece of 7/16" (11mm) diameter static (low-stretch) rope, such as Blue Water II. Also obtain a 24" piece of 1" diameter tubular webbing, in the color of your choice (also available where you buy climbing rope). Tie a figure-eight knot in one end of the rope, leaving a small loop for one auto-locking carabiner. Slide the webbing over the free end, and tie another figure-eight knot in the free end, capturing the webbing and making another small loop for the second auto-locking carabiner. You should have about 3-4 inches in the loose rope end adjacent to each knot. Try the lanyard out on your tower, passing it around or through the tower in various combinations. Once again, after you are satisfied with the length, tape the loose ends from the knots to the main rope for neatness and an extra measure of security that the knot will not come undone. Notice that the webbing acts as a sacrificial abrasion element for the main rope, and also as a color code. If you climb more than one size of tower and make more than one lanyard, assign a different webbing color to identify the lanyard length. CORROSION PREVENTION DISSIMILAR METALS AND GALVANIC ACTION These corrosion problems can be prevented by using a joint compound which can cover and prevent the bridging of moisture between the metals. The most popular compounds use either zinc oxide or copper particles embedded in a silicone grease. As the joint pressure is increased, the embedded particles dig into the metals and form a virgin junction of low resistivity which is void of air and its moisture. The following is a list of paste and grease-like products for the prevention of oxidation of aluminum in electrical connections and antenna installations: ---------------------------------------------------------------- Manufacturer: Butternut Electronics Company 831 North Central Avenue Wood Dale, IL 60191 Tel: (708) 238-1854 Fax: (708) 238-1186 Product Name: Butter-It's-Not Source: Direct if not stocked by local authorized dealer. Price: $3.50/ Envelope NOTES: Contains copper dust in a molybdenum suspension. ----------------------------------------------------------------- Manufacturer: GB Electrical 6101 N. Baker Road Milwaukee, WI 53209 Tel: 1-800-558-4311 Product Name: OX-GARD Source: Available from many electrical supply houses and retail outlets such as Sears, Home Depot, Ace and True Value Hardware stores. No Factory direct sales. GB catalog number OX-100B. Price: Approximately 3.00/ 1-oz tube ----------------------------------------------------------------- Manufacturer: Ideal Industries, Inc. Becker Place Sycamore, IL 60178 Tel: 1-800-435-0705 and: 1-815-895-5181 Fax: 1-800-533-4483 Product Name: NOALOX Source: Distributors (Call 800 number for nearest one) Price: Ideal list price $2.58/ half oz tube (#30-024) and $8.64/8oz bottle (#30-030). NOTES: Also available from many electrical wholesale supply houses. No factory direct sales. Contains zinc particles suspended in a carrier. ----------------------------------------------------------------- Manufacturer: KLM Antennas Inc. PO Box 694 Monroe, WA 98272 Tel: 1-360-794-2923 Fax: 1-360-794-0294 Product Name: Conductive Paste Source: Factory direct and larger dealers. Price: $3.50 plus shipping & handling/ 1 ounce containers NOTES: Anti-seize thread compound Hi-Temperature MIL-A-907E. Contains copper and graphite flakes suspended in a petroleum base. Manufactured for Mirage/KLM by Chemical Commodities Agency, Inc. of Highland, CA per MIL-A-907E. ---------------------------------------------------------------- Manufacturer: Sanchem, Inc. 1600 S. Canal Street Chicago, IL 60616 Tel: 1-800-621-1603 Out of State: 1-312-733-6111 Fax: 1-312-733-7432 Product Name: NO-OX-ID Source: Direct from Manufacturer Price: $11/16oz can or $8.80/8oz tube (plus shipping) Minimum order - $35 NOTES: NO-OX-ID comes in several consistencies. NO-OX-ID "A" and NO-OX-ID "A-Special" are suitable for most antenna installations. NO-OX-ID "A-Special" is similar to NO-OX-ID "A" but has a small amount of solvent added for ease of application. ----------------------------------------------------------------- Manufacturer: Thomas & Betts Company 1555 Lynnfield Road Memphis, TN 38119 Tel: 1-800-888-0211 Fax: 1-800-888-0790 Product Name: Aluma-Shield Source: No direct factory sales. Available from many electrical supply distributors. Price: Approximately $11.44/ 8oz can. NOTES: Customer may call 800 number for location of nearest distributor. Contains zinc particles suspended in a petroleum base. ----------------------------------------------------------------- Manufacturer: Burndy Electrical 101 E. Industrial Park Dr. Manchester, NH, 03108 Tel: 1-800-346-4175 Fax: 1-800-346-9826 Product Name: Penetrox (PEN-A) Source: Electrical wholesalers Price: Approx. $6/ 3oz tube NOTES: Zinc particles suspended in a natural based compound. Penetrox A is a natural (petroleum) based compound with evenly suspended zinc particles. It is recommended for aluminum to aluminum, aluminum to copper, and aluminum to plated copper connections. It is not recommended for use with rubber or polyethylene insulated conductors. UL listed to 600V. Penetrox A-13 is a synthetic base compound with evenly suspended zinc particles. It is recommended for aluminum to aluminum, aluminum to copper connections. It is compatible with rubber, polyethylene and other insulating materials. UL listed for all voltages. Penetrox E is a synthetic base compound with evenly suspended copper particles. It is recommended for copper to copper, copper threads, and all grounding applications. UL listed. ----------------------------------------------------------------- Manufacturer: Ilsco Corporation 4730 Madison Road Cincinnati, Ohio 45227 Tel: 1-513-533-6200 Fax: 1-513-533-6274 Product Name: DE-OX Source: No factory direct sales. Available from electrical supply wholesalers and distributors. Customer may call for nearest distributor. Price: Approximately $2.90/ 1oz, $4.90/ 4oz and $7.30/ 8oz squeeze bottle. NOTES: Used in the electrical trade for Al/Cu and Al/Al connections. Green colored grease with no noticeable particles in suspension. ----------------------------------------------------------------- Manufacturer: Antennas West PO Box 50062 Provo, Utah 84605 Tel: 1-801-373-8425 Fax: 1-801-373-8426 Product Name: Goose Grease Source: Factory direct sales only. Price: $1.00/ 1oz + and $1.00 p&h. NOTES: Transparent silicone grease. Antennas West also recommends this product for ground rod clamp connections. ----------------------------------------------------------------- Manufacturer: Mosley Electronics, Inc. 10812 Ambassador Blvd. St. Louis, MO 63132 Tel: 1-800-966-7539 and: 1-800-325-4016 and: 1-314-994-7872 Fax: 1-314-994-7873 Product Name: 1) Mosley Penetrox (Conductive Grease) 2) Weather Guard (Clear spray coating) Source: Factory direct sales only. Price: Mosley Penetrox- $4.45 / packet + postage. Weather Guard- $12.75/ 8oz spray can + shipping NOTES: Mosley Penetrox is a grease like product. Weather Guard is a clear spray especially recommended for marine and coastal environments. Weather Guard cannot be shipped via the post office; UPS required. ----------------------------------------------------------------- Manufacturer: Loctite Corporation 1001 Troutbrook Crossing Rocky Hill, CT 06067-3910 Tel.: 800-842-0041 Product Name: Permatex ANTI-SEIZE LUBRICANT Source: Many Automotive Supply Distributors Price: N/A NOTES: Comes in 1 oz squeeze tube, 8 fluid oz brush top container, and a 12 oz aerosol can. Can be used on the threads of U-bolts to prevent "seizing, galling, and corrosion." It aids in the disassembly of the antenna's hardware. Not for use on electrical connections. The part no. on a 1 oz tube is 133A. ----------------------------------------------------------------- The connection of a copper wire to galvanized tower leg should be avoided even if joint compound is used. The primary problem here is that due to dissimilar metals, the galvanizing will eventually be eaten away. In addition, there is very low surface-area contact of the round wire with the (round) tower leg. A copper strap should be used instead. In this case, use a washer material between the copper grounding strap material and the tower legs. The most common thing to do is use a thin sheet of stainless steel (machinist's shim stock). You could also use lead, tin, or silver, or you can simply tin (soft solder) the end of the copper conductor that will be clamped to the galvanized steel. Consider using a clamp such as or similar to the PolyPhaser TK series stainless steel clamp as shown on page 53 of the '90-'91 Catalog. The TK clamp will help increase the surface area of the connection as well as provide the necessary isolation between the dissimilar metals. Be sure to use antioxidant/joint compound on all contact points. For an even more effective connection, use copper strap in place of the wire with the TK series. Beyond that, it would be very beneficial to seal the connection with your favorite "liquid tape" or Scotchkote and vinyl electrical tape to keep moisture out of the joint. The moisture is the electrolyte that turns the dissimilar metal joint into a battery. Silver oxide is the only oxide (that we know of) that is conductive. This is one reason why PolyPhaser's N-type coax connectors are all silver with gold center pins. Copper oxide is not conductive and the proper application of joint compound will prevent oxidation. Knowledge of corrosion can make the difference between a good site that stays on the air and one which needs a lot of maintenance after a short period of time. Noble Metal Table: Accelerated corrosion can occur between unprotected joints if the algebraic difference in atomic potential is greater than +-10.3 volts. MAG. ALUM. ZINC IRON CAD. NICK. TIN LEAD COPPER SILVER PALL. GOLD MAGNESIUM 0.00 -0.71 -1.61 -1.93 -1.97 -2.12 -2.23 -2.24 -2.71 -3.17 -3.36 -3.87 ALUMINUM 0.71 0.00 -0.90 -1.22 -1.26 -1.41 -1.52 -1.53 -2.00 -2.46 -2.65 -3.16 ZINC 1.61 0.90 0.00 -0.32 -0.36 -0.51 -0.63 -0.64 -1.10 -1.56 -1.75 -2.26 IRON 1.93 1.22 0.32 0.00 -0.04 -0.19 -0.30 -0.31 -0.78 -1.24 -1.43 -1.94 CADMIUM 1.97 1.26 0.36 0.04 0.00 -0.15 -0.27 -0.28 -0.74 -1.20 -1.39 -1.90 NICKEL 2.12 1.41 0.51 0.19 0.15 0.00 -0.11 -0.12 -0.59 -1.05 -1.24 -1.75 TIN 2.23 1.52 0.63 0.30 0.27 0.11 0.00 -0.01 -0.47 -0.94 -1.12 -1.64 LEAD 2.24 1.53 0.64 0.31 0.28 0.12 0.01 0.00 -0.46 -0.93 -1.11 -1.63 COPPER 2.71 2.00 1.10 0.78 0.74 0.59 0.40 0.46 0.00 -0.46 -0.65 -1.16 SILVER 3.17 2.46 1.56 1.24 1.20 1.05 0.94 0.93 0.46 0.00 -0.19 -0.70 PALLADIUM 3.36 2.65 1.75 1.43 1.39 1.24 1.12 1.11 0.65 0.19 0.00 -0.51 GOLD 3.87 3.16 2.26 1.94 1.90 1.75 1.64 1.63 1.16 0.70 0.51 0.00 LESS NOBLE CATHODIC PROTECTION Cathodic protection is a process of using the known variables of a corrosion cell to effectively mitigate the detrimental effects of corrosion. There are two types of cathodic protection commonly used. The easiest is known as galvanic anode protection. This is accomplished in tower anchor systems by electrically bonding sacrificial anodes to the anchor support, making the galvanic corrosion cell current flow away from the sacrificial anode and toward the anchor shaft and copper ground rod. Because the anode is higher on the galvanic chart, it will corrode instead of the anchor or tower components. Sacrificial anodes vary widely in their sizes, shapes and make-up. Anodes are typically made of magnesium or zinc. The anode is usually placed in a cotton bag surrounded by a gypsum, bentonite and sodium sulfate mixture. This mixture is used for the purpose of assisting in the activation of the current flow and to ensure that moisture remains around the area of the anode. A wire is attached to the inner core of the anode and is designed to be bonded electrically to the member to be protected. Following installation of the galvanic anode cathodic protection system, it is essential that it be monitored regularly to ensure its proper operation. A DC volt meter and copper/copper sulfate reference electrode (half-cell) is the most common method of checking the system after its installation. The tip of the half cell is placed in the soil with one lead of the volt meter connected to it and the other to the structure being tested. The measurement should show a voltage shift from the same test conducted on the structure before the system installation. PROTECTING ANTENNAS FROM CORROSION One good way of protecting your shiny new aluminum and copper contraptions from corrosion is to paint them with a protective paint. There are two types you can use. Clear acrylic lacquer will do a good job for at least a few years. Another product that has lasted 15 years near a salt water environment is X-I-M 900, a clear metal primer, which may be harder to find. You may have to visit a professional paint store to find it. In any case, clean the metal thoroughly with a scotchbrite pad. DO NOT use steel wool or sandpaper, both of which will leave behind residues. Then, degrease it with rubbing alcohol, let it dry, and apply 3 coats of the paint. If the paint you use is not a spray paint, the best thing to use is a paint mitt. First, put a plastic baggie over your hand, put the mitt on, dip it in the bucket and grab the surfaces with up/down or back/forth motions. The mitts are available from CESCO and other suppliers. Get several pairs and throw them away when you're done. DO NOT paint polycarbonate plastic parts (Lexan), such as the element clamps on KLM beams. The paint WILL react with the plastic and result in fatal cracking. You should be VERY careful about approaching polycarbonate plastic with ANY volatile hydrocarbon solvent in general (paints, adhesives, lubricants, threadlockers). Until you know for sure that the stuff is compatible with the plastic, keep it away! PROTECTING THREADED FASTENERS ANTI-SEIZE FOR FASTENERS The Principles, behind seizing prevention are not very different from those of applying "GOO" to your antenna electrical connections. Both types of "joint compound" have a liquid vehicle to carry some kind of solid particles into the connection. Regardless of the application (electrical or mechanical) the purpose of the liquid vehicle is to readily allow the application to spread and deposit the suspended solid particles to all mating surfaces. Once, this has been accomplished, the job is really done by the solids. The materials were designed this way, and our experience verifies it! Any of us, who have applied some kind of "Goo" to a connection have observed that after some amount of time, the compound dries up and all that is left in the connection is the solid material. This is caused by a natural leaching process, whereby the repeated depositing and flushing activity of moisture in the connection washes the liquid vehicle out of the connection. We also observe that some of the solids are also washed out, but fortunately, some of them are left in the connection to do their job. In the anti-seizing application, the solids are almost always softer than the parent materials (parent materials refers to the material on either side of the connection, like 300 series stainless in the nut & bolt of a connection, or forged steel on each side of a good turnbuckle.) They are also trapped in between the mating thread interfaces mechanically by the pressure created by tightening the fasteners. When we come along years later to undo the connections, the trapped soft particles get chewed up and destroyed, preventing the parent materials from coming into contact with each other and galling. As stated in the previous post, identical parent materials will want to gall, or deform equally together to distort each other, causing a mechanical lock. Sometimes, an effective anti-seizing solid may be harder than the parent materials. In this case, the joint will come apart, but damage will be done to the parent materials requiring replacement. The key for the anti-seize solid to be effective is for it to have a different hardness than the mating surfaces. The softer solid is preferred as it allows the mating parts to be reused. The galvanic corrosion problems with certain solids are addressed above. The selection of an anti-seizing compound is directly connected to the environment your hardware will be exposed to. If the connection is going to be flooded with repeated moisture on a daily basis, you need to use a compound that will ~ot completely exit the connection. If your environment is relatively dry (moisture condensing on the hardware 1/3 of the year) you can use almost anything. There is a product called "LeadPlate" that can be used in a variety of applications. Several of the applications have been high temperature aerospace. The really neat aspect of this type of product is the extremely soft nature of the lead solids. They seem to very easily deform and stick to the mating surfaces. When the vehicle goes away, the lead particles are still stuck to the mating surfaces, by virtue of soft malleable nature of the lead, so that the connections always came apart. Permatex (Tm) anti-seize can be used on all threaded connections. This compound is very clearly silver in color. It can protect fasteners even after 10 years. The toughest application is for hardware on sailing yachts. The empirical history on this experience has proven that all common anti-seize compounds behave well initially. When they are exposed to daily washings of condensation, as is experienced by anything on the ocean, All of the good stuff goes away, and the poor guy trying to take the hardware apart ends up spending 80% of his time getting it apart, 10% of his time getting the local machine shop to make new parts, and 10% of his time putting it all back together. So, what is the good stuff? Its name is Tef-Gel. It is Teflon based and is not cheap. Both the vehicle and the solid seem to stay in the connection! This product is still there, to do its job, where all of the others were washed away. Reminder, this discussion is aimed at preventing things that must move from getting locked up! Tef-Gel is sold in the marine distribution chain. I would suggest that you look for general marine retail outlets. In the U.S. there is a company called "Port Supply" that has several retail outlets along both the western and eastern coasts. THREAD LOCKING Time to get back to some of the simple stainless connections on amateur antennas and towers that we don't need to move, but need to stay put. Simple thread-locking compounds can be used with success. The fascinating thing about these connections is that, the "thread-locking" Blue Loctite provides enough lubrication to the connection to prevent galling. The compound cures properly, when the parts are not contaminated with oils, it seals the connection off from moisture, and its eventual corrosion, and is easily disassembled later. When we put a thread-locking compound into a threaded connection, the outer threads, exposed to the air do not completely cure. The material inside the outer thread rings completely cures. The next neat little feature of the thread-locking materials is that when they cure, they expand. The expansion of the compound applies pressure to the mating thread faces and locks the fastener. Better antenna building through modern chemistry! The locking feature of the compound is essential, as the anti-seizing compounds cannot provide a lock. They are designed to prevent a lock. Gets confusing, Eh? Blue compounds are the low strength type. They are usually called "threadlocker" or some such name. Red compounds are the medium strength type. They are called "bearing mount" or .... Green compounds are high strength types and should be associated with terms like "nuclear bomb" or "cruise missle" when thinking about getting them apart. If you are putting semi-permanent stainless fasteners together, use the "Blue" thread-locking Loctite. Critical connections that make masts fall down and kill people get the "Red" or "Green" Loctite. Things that require regular service and lubrication get the Tef-Gel (like noisy tubular towers). Again, you should be VERY careful about approaching polycarbonate plastic (such as the Lexan parts on KLM antennas) with ANY volatile hydrocarbon solvent in general (paints, adhesives, lubricants, threadlockers). Until you know for sure that the stuff is compatible with the plastic, keep it away! WATERPROOFING CONNECTIONS Having been involved with DB Vapor wrap, Scotch 88 tape and ScotchKote on hundreds on professional and amateur antennas over the past 20 years, I would like to make an observation. #1 Putting a wrap or two of 88 tape on the connector and or feedline and then putting the Vapor Wrap on top will keep water out in 75% of the installations. Why only 75%? Well, 25% of the time air is trapped and leaves a gap. Where there is air, there will be water. #2 When Vapor Wrap is put right on the connector and then 3 wraps of 88 tape are put on top, followed by ScotchKote (left to dry for a few hours) and 1 more wrap of 88 tape, our connections have been 100% waterproof. #3 I have never had trouble taking Vapor Wrap off of a connector. It takes some practice, but you can use the wrap to stick to itself and it peels off. #4 I have HAD trouble taking COAX SEAL off any connector where a ham called me in to find out why water got in his coax. #5 If you don't put a wrap of tape over the ScotchKote you will find that the ScotchKote will be gone in about a year. The sun dries it up and allows it to flake away. Put a wrap of 88 tape on top and it is there for a long time. Black-colored Liquid Electrical Tape (LET), made by Starbrite, can also be used in place of the ScotchKote. It may even be preferred since ScotchKote is not rated for UV exposure, and the black LET is. You can restore old containers of LET that have become thick and gummy by thinning the contents using small amounts of the solvent MEK (methyl Ethyl Ketone.) CoaxSeal, or similar products, is used as a vapor barrier to keep moisture out of a coax connector joint. I'm not a big fan of CoaxSeal because it's not a quality vapor wrap like what professional communications installers use. Tower Tech carries a butyl rubber vapor wrap by DB Products, a supplier of professional communications products and we sell it by the foot. It runs $3.00 per foot (it's 3 inches wide). The most important thing to remember when using any material like this is that you need to apply electrical tape over the connector FIRST, and then apply the vapor wrap. Pull the tape very firmly over changes in diameter to eliminate as many wrinkles as possible. Wrinkles in the tape are death to a good seal! Putting CoaxSeal directly on the connector renders the connector unusable if you ever try to reuse it -- it just gunks everything up. Put 2 layers of tape over the vapor wrap and that'll give you a professional, bombproof joint. Here's another hint: apply the last layer of electrical tape (you are using Scotch 33 or 88, aren't you?) so that it runs UP the coax. Then let the tape relax before you apply the very end; that'll minimize the flagging that can take place. That way water will run down the layers of tape and not INTO them. It's like shingles on your roof; if the tape is applied in a downward direction, the tape laps actually channel running water into the joint. BTW, ScotchKote is a liquid that is applied to the electrical tape when you finished the above steps and it gives additional weather proofing to the joint. By coincidence, Tower Tech has it for $16.00 per bottle. An extra measure of oxidation prevention can be achieved by applying a light coat of silicone grease to the contacts in the RF connector. The best grease to use is Dow Corning's "silicone high vacuum grease". By preventing the intrusion of any moisture or other contaminants, (electrolyte is excluded), corrosion cannot form. ACCESSORY MATERIALS AND SERVICES INSULATING MATERIAL High pressure phenolic laminated sheet makes an excellent insulating material for antenna systems. In the industrial plastics world this material is known as "Grade LE Phenolic Laminated Sheet" and any industrial plastics company should have it. A trade name for this material is Garolite. McMaster-Carr carries it. The material is extremely strong and completely impervious to weather (I've had many pieces in use for over 25 years with no significant deterioration!) Standard thicknesses include .250 .312 .375 .437 .500" If u can't find a supplier, I purchase mine from Read Plastics in Rockville MD, (301)881-7900. ELECTRICAL TAPE Don't bother using anything other than Scotch Super 33 or 88. Nothing else stands up to the weather or sunlight. ACCESSORY STEP The general consensus is that these slip on shelves for Rohn towers, although convenient, tend to just get in the way. ROTOR REPAIR Norm's Rotor Service: http://www.tiac.net/users/shiacawn/rotors/ and can be reached at 301-874-5885. Rotor Doctor (formerly CATS): http://www.rotordoc.com craig@rotordoc.com 7368 S.R. 105, Pemberville, OH 43450, 1-419-352-4465 Fax: (419) 353-2287 1-800-3ROTORS Linda at Hy-Gain (everybody buys their parts from the factory) is at 402-465-7021. FIBERGLASS SPREADER RODS Max Gain Systems 221 Greencrest Court Marietta, Ga. 30068 770-973-6251 http://www.mgs4u.com Cubex Co. CRIMP-ON PL-259 CONNECTORS Connectors Unlimited P.O. Box 5973 Manchester, NH 03108-5973 Phone 603-668-5926 Fax 603-641-1179 Their catalog has a lot of connectors (F, UHF, N, BNC, etc) for dozens of cable sizes. And the appropriate crimp tools. With prices. PULLEYS REI/Recreational Equipment Incorporated, 800 426 4840 and www.rei.com. Pulley REI# ropes side sheave strength wt price(May 97) up to plates REI Blue 471-424 ?" alum nylon 4500lb 2oz $10.00 CMI RP101 471-211 5/8 alum nylon 3500 5oz $19.25 CMI RP103 471-210 5/8 alum alum 5000 6oz $39.00 CMI RC104 471-073 5/8 steel steel 10000 1lb $48.50 CMI RP108 471-084 5/8 steel alum 16000 2lb $65.00 TOWER BOLTS I got a large shipment of Rohn bolt kits in yesterday so I can fill your orders again. Here are the items and prices of the stuff I can supply: JR45A U-bolt with nuts for AS25G (25G rotator shelf) .32 each JR51A U-bolt with nuts for AS455G (45G/55G rotator shelf) .83 each 25JBK 25G bolt kit (6 bolts, 6 nuts) 1.44 each 45JBK 45G bolt kit (6 bolts, 6 nuts) 3.14 each 55JBK 55G bolt kit (6 bolts, 6 nuts) 3.87 each Here is the procedure: You determine which items you need and how many. Figure the cost of the items and send me an email showing your totals and your mailing address, including zip code. I will package the items, have them weighed at the local post office to determine the shipping charges, and send you an email with the grand total, including shipping charges. You send me your check, Postal Money Order, or cash (slightly risky) and I will send you your hardware. The UPS office is 15 miles from here and using "Mail Boxes Etc." is way too costly. The Post Office is only 4 blocks and is the least expensive. Stan w7ni@teleport.com TOOL AND PART POUCHES There is a guy that makes handy little pouches for tower work. No other number on his literature. Tower-Mate 25 $15.95, Tower-Mate 45 $19.95 Tower-Mate PO Box 601616 Sacramento, CA 95860-1616 Fax #916-481-5381 Champion Radio Products 888-833-3104 http://www.championradio.com COLD GALVANIZING PAINT KLEIN or LPS make high content, zinc-bearing paint. DAP also makes GALV-A- GRIP in quart cans. ROTATORS SELECTION Data taken from manufacturer's web pages. Price is lowest price found in 1998 Rotating and Braking torque in ft-lbs. Model Price Rotating Braking K-factor Yaesu G450 239 40 217 722 HyGain CD45 320 50 67 1200 Wilson WR-500 ??? 65 108 HyGain HamIV 440 67 416 2800 Yaesu G800 400 79 288 1299 Yaesu G1000 480 79 433 2020 HyGain T2X 530 83 750 3400 Create RC5A2 670 116 1443 Emoto 1200FXX 780 143 1290 Create RC5A3 770 159 1443 Create RC5B3 1300 159 1804 Yaesu G2800 1150 181 1808 6870 M^2OR 2800P 1270 208 1416 Emoto 1300MSAX 1300 215 1792 HyGain HDR300 1100 417 625 5000 Create and Emoto have many more models than listed above. You can find some of this data and a LOT more at: http://www.hygain.com/rotors.htm http://www.yaesu.com/rotors.html http://www.m2inc.com/cats/prods/or2800p.htm http://www.elecdist.com/emoto.html http://www.elecdist.com/create/rotors.html The following rotors will fit into Rohn 25G tower sections without modifying the tower: Yaesu G450, G800, G800SDX, HyGain Ham IV, The following rotors will NOT fit into a Rohn 25G tower section unless a brace is bent or removed: HyGain T2X, ROTOR WIRING COLOR CODING TIP. To use, just take the two heavier conductors (if there are any in your cable) and attach them to pins 1 and 2 (alphabetically), then take the remaining wires and attach to pins 3 through 8, alphabetically. Voila! Most rotators use a similar scheme for motor control and indicator. Their operation is sensitive to voltage drop so the proper sized cable is real important. Hy-Gain recommends the following: Max. length Gauge for Terminals 1 & 2 Term. 3-8 125' #18 #22 200 16 20 300 14 18 500 12 16 800 10 14 If you've got some smaller wire, you can twist multiple conductors together to give you a 'bigger' wire size. The rule is: two wires of the same size are equal to one wire which is two sizes larger. The well-known technique of mounting the Hy-Gain starting capacitor close to the rotator is a good one. The Japanese rotators use DC motors. ROTOR WEIGHT DISTRIBUTION The bearing in most rotors are designed to accommodate the vertical weight load placed on them by a mast and antenna assembly. Relieving this vertical load completely through the use of thrust bearings may actually shorten the life of the rotor in a windstorm since the bottom end of the mast may be more prone to dancing around if all the weight is being supported up higher by the thrust bearing. The preferred method is to let the entire weight of the mast and antenna assembly bear on the rotor and to gently snug up the thrust bearing centering bolts. However, if the mast and antennas are exceptionally heavy, some load can be shared by the upper thrust bearing. Again, the use of two thrust bearings would prevent the mast end from moving around too much and damaging the rotor. The trick here is not to tighten both thrust bearing bolts snugly against the mast, but only enough to keep it from flopping around. This also allows the mast weight to bear on the rotor, stabilizing its bearings. PHYSICAL INSTALLATION TIGHTENING SEQUENCE Here is a neat, simple trick to insure the best alignment. This is a specific sequence of hardware tightening that helps insure good physical alignment. 1. Close, but don't tighten, the mast clamp bolts of the thrust bearing. If you are using a second, lower thrust bearing, leave its clamp bolts loose. The mast should be gently centered by the uppermost thrust bearing, but not prevented from moving vertically. 2. Clamp the rotator to the mast. 3. Tighten the rotator mounting bolts to the rotator plate. 4. Tighten the U-bolts of the rotator plate to the tower legs. 5. Tighten the mast clamp bolts on the uppermost thrust bearing. 6. Do not tighten the mast clamps bolts on the lower, intermediate thrust bearing, to account for any slight bow in the mast or misalignment of the rotator itself. TROUBLESHOOTING ROTATION PROBLEMS If you have a brand new installation, stop and check if you used the proper gauge rotor wire to account for the length of your installation, and that you used the two heaviest gauge wires on the appropriate terminal numbers. This varies with the rotor make and model, so refer to the manufacturer's literature. Undersized rotor cable causes a voltage drop that will interfere with proper operation. Also, double-check your terminal and connector pin wiring and color codes with the literature. Make clear diagrams of all of your connections to be sure you made them correctly. When your new rotator still doesn't seem to be working properly, or when an existing installation stops working, a friend and a tower climb are in order to perform a series of checks to determine where the real problem is. Take your HT with you up the tower and ask a friend to stand by in your shack with his HT so you can coordinate the tests. Check the entire length of the rotor cable from the shack to the rotator for damage as you go up. First, loosen the rotator's mast clamps and attempt to turn the mast and antennas by hand. See if the mast is binding in any particular portion of its rotation. If so, this could indicate a problem with the thrust bearing or some other mechanical interference with the antennas, feedlines, or perhaps nearby obstacles. If you suspect the thrust bearing, loosen the mast clamp bolts on it and try turning the mast again. If free, your thrust bearing may be clogged with debris or corroded. If you cannot clear the problem, leave the clamp bolts slightly loose and re-clamp the rotator. It should work fine even if the thrust bearing race is not turning with the mast. If the mast and antennas turn ok, call your friend and have them run the rotator back and forth between its limits. Watch and listen for smooth, continuous motion and sound from the rotator throughout its range of motion. If there is a problem here, you may see some erratic motion or even hear sounds from the gearbox that always occur in the same portion of movement. If you see any of these problems or if your rotator is ten years old or more, you probably need to service it or replace it. If the rotator does not start turning readily when it is loosened from the mast, your motor starting capacitor (usually in the control head) may possibly need to be replaced. If both the mast and the rotator turn freely separately, but not together, you may have an alignment problem. Work back through the tightening sequence in the previous section. If you still have a problem, look for physical problems that may prevent the rotor from being level or centered in the tower, that may not be accounted for in the tightening sequence. This may become obvious if you encounter binding of a component during the sequence. You may also have a rotator that does not have self-centering clamps. These types require a shim for smaller diameter masts to keep the mast centered when the clamps are tightened. HYGAIN ROTOR PRIMER The following was provided by Gary Kunkee, rotator repair man at Telex- HyGain, an authority on the Ham-M, II, III, IV, V series rotators. The basic hardware of the rotator hasn't changed much with the notable exception of a change from a zinc gear to steel and an internal wiring change (different ordered use of the 8 terminals). Most all parts are interchangeable to this day. HYGAIN ROTOR IDENTIFICATION There were 5 series of Ham M until 1972 whereupon the name changed over time to Ham II, III, IV and V. Look for a four digit number on the Brake Casting (one with terminal strip on it). Some units may not have this number (I think). The first digit may be 1 through 5 indicating Series 1 through 5 of the Ham-M. The Ham II, etc. should be stamped as such (Roman Numeral number). I think the Ham V is actually a Ham IV with a fancier control box. The next three digits indicate the week (2 digits) and year of manufacture. HYGAIN ROTOR LUBRICATION Grease is used modestly, not "packed" as may be commonly thought. Currently they use a product called Nyogel 727F but a low temperature white lithium grease is usable instead. Nye Lubricants, New Bedford, MA, Ph: (508)996- 6721. HYGAIN ROTOR INTERNAL WIRING The main control box transformer is either a 120 or a 240 VAC input winding. It puts out typically 30VAC under load. But 26 to28VAC is okay too. He usually measures 1.5A up to 2.0A current draw. If more than 2 amps is drawn he usually changes the motor. The Series One and Two can be internally rewired to the later standard and be used with the newer control boxes. One giveaway (internally) on these two series is a wire between the pot and to limit switches. Later models do not have this wire. Measurements made on the various terminal combinations with certain results can determine which of the two wiring standards you have. The motor start capacitor, in the control box, is a 130 microfarad, 110- 125VAC, non-polarized electrolytic. A similar replacement is available from Grainger. Grainger part number "4X059" is a 130-156mfd, 110-125VAC, non- polarized electrolytic. Physically it fits in the existing mounting clip, but rather than axial leads, it has two "plug in prongs" at one end, so you need to save the longer leads from the old unit and solder them to the prongs. There's also a physically identical part "4X058" which is 108- 130mfd. Since the original is 130mfd, the 4X058 would probably work as well. HYGAIN ROTOR TYPICAL ELECTRICAL MEASUREMENTS Typical Measurements on Rotator Terminal Strips: Ham-M Series 1 & 2 Between terminals: 1&2 0.75 Ohms Brake Solenoid 1&3 2.5 Ohms Motor Winding 1&4 2.5 Ohms Motor Winding 1&5 2.5 Ohms Motor Winding 1&6 2.5 Ohms Motor Winding 3&4 5.0 Ohms Whole Motor 3&5 Short 4&6 Short 3&7 500 Ohms Position Feedback Pot.- end to end 3&8 0 to 500 Ohms Pot.- One end to wiper arm 8&7 0 to 500 Ohms Pot.- Other end to wiper arm Wiper is No. 8 on this series Ham-M Series 3 to 5, Ham II, III, IV, V Between terminals: 1&2 0.75 Ohms Brake Solenoid 1&8 2.5 Ohms Motor Winding 1&4 2.5 Ohms Motor Winding 1&5 2.5 Ohms Motor Winding 1&6 2.5 Ohms Motor Winding 8&4 5.0 Ohms Whole Motor 8&5 Short 4&6 Short 3&7 500 Ohms Position Feedback Pot.- end to end 3&1 0 to 500 Ohms Pot. One end to wiper arm 1&7 0 to 500 Ohms Pot. Other end to wiper arm YAESU ROTOR PROBLEMS There have been several problems reported with the 400, 800, and 1000 series Yaesu rotators, relating to the control box drive motor and circuitry. The early ones seemed to have cheap drive motors in the control box. the motor commutator segments were too soft and after some time the copper would wipe and fill the commutator gaps. If not caught quickly enough this can smoke the two small current-limiting resistors in the drive circuit. it seems like the resistors act as fuses and protect the drive transistors, so bigger resistors may not be the fix here. The replacement motors seem better so maybe they found a better one. Here's a temporary fix for the motor on the G-1000 SDX control unit: Unplugging the control cable should cause the needle to go to the counter clockwise stop on the indicator. If not, it probably means the indicator drive motor is bad. This is a common problem with the Yaesu G series of rotors. For a quick check to see if that is the problem do the following: 1. Remove the metal cover (2 screws on sides and 4 feet) 2. Remove front panel (3 screws on bottom, 2 on top) 3. Pull front panel out about 1-2cm and look in to the gear mechanism on the left side. you should see a small pulley with a rubber belt on it. 4. Plug in the rotor power but remove the control cable. Be careful, there are exposed connections where line power is available but they are on the bottom side of the front panels on the other side of the indicator at the switch. 5. Turn on the rotor. With a small screwdriver, gently try to turn the small pulley with the rubber belt. If it starts to slowly turn the needle, it confirms the motor is the problem. If it doesn't start operating, it could still be the motor, but may also be the control board. If it goes back at full speed, it might have been a mechanical jam but that is less common. What typically happens is that the commutator segments in the motor are too soft so after a while the metal 'wipes' and powders enough to get in between the commutator segments and essentially shorts out the motor. If the controller is left on for long periods in this condition it can also burn up the 2 current limiting resistors and/or drive transistors on the little circuit board behind the motor (see below). Giving the motor a push gets it past the shorted spot and at least shows you that the rest of the drive and control stuff is working, but it won't last. A temporary fix goes as follows: 1. Starting from where you left off above, pull the power plug. 2. Remove the small circuit board behind the drive motor (4 screws) 3. With needle nose pliers, uncrimp the 3 crimps that hold the plastic back onto the metal case of the motor. 4. Very gently pry the plastic back off the motor. 5. Using a needle or other very small type of dental pick tool, carefully scrape the gunk out from between the segments of the commutator. You can remove the small nylon washer on top of the shaft for better access. 6. Use a paper clip or small pair of tweezers inserted through the small slots on the plastic back to hold the commutator brushes out of the way and carefully replace the plastic back. 7. Re-crimp the metal back and replace the circuit board. This should restore operation for a while, but eventually the motor will need to be replaced. This process is much more involved as you have to disassemble basically the whole front panel to get to it. R1 and R2, referred to above, are 120 ohm, .5 watt resistors in the control head. The control head motor draws about 40 ma when working (no binding etc) so that draws .2 watts of power through either one of the resistors. If the motor binds/stalls or shorts, the current goes up to 110ma which means about 1.5 watts in R1 or R2. This is a significant overload. You can replace them with 5 watt 150 ohm units from the junk box and run the unit with the motor shorted (clip lead) for several hours. It will get warm but will survive. Q1/Q2, the motor drive transistors, actually show very little temperature rise during this, indicating that they are not being worked very hard. If the tower-mounted pot opens (or the leads are off etc) the control box will turn the pot motor to one end and then stall, and if left would burn out the factory resistors. So if you just energize the control box WITHOUT the pot in the rotor connected, you will cause either one of R1/R2 to deal with 1.5 watts, a 300% overload. This is not what you'd call an intelligent design. And you won't see any warnings about this in the manual......Any shorts external to the rotor would not cause R1/R2 to be damaged as they are several levels removed from the output. However, anything that causes the bridge balance to be upset enough that the motor/pot in the indicator cannot find the null will cause the motor to stall out at one end or the other. If you transmit and the indicator moves, you have an RF problem. Higher wattage resistors prevent damage, but they are not the cause or cure of the original problem. You can test your unit on the bench using an external 500 ohm pot on terminals 2 and 3 to simulate the pot in the rotor. If the motor shows no signs of binding, but then only works for a day or so when put back into service, you have to assume that there is a problem with the pot or cabling in the actual rotor. The other common problem is the mast clamp castings, which are brittle and tend to break on installation. ATTACHING COAX AND CONTROL WIRES ROUTING CABLES Run your coax cable and control wires up inside the framework of the tower, next to one of the legs. This way, the tower provides two types of protection. First, the tower will protect the lines mechanically from falling/flying tree limbs, tools, antenna parts, etc (during tower work or a storm), haul lines, or anything else that may bang into or snag on the tower. Second, the tower cage acts like a faraday shield to help protect the lines electrically from EMP (nearby lightning) and direct tower hits from lightning. ATTACHING CABLES TO TOWER Scotch 33+ or 88 makes an excellent cable clamp that, when applied correctly, will withstand the rigors of weather, the sun, and time. Do NOT use cheap vinyl electrical tape unless you like climbing and duplicating your efforts. Start taping at the top and work your way down, taping every 5 feet - that?s twice per tower section. Lift the lines up slightly before each taping to take the strain off of the cables. This way, each tape wrap is only supporting the weight of the 5 feet of cabling below it. Start each tape point with two turns around the tower leg itself, then 4 turns around the cables, snugging them gently with moderate tension. Apply each new turn over the previous one with 100% overlap - do not spread the turns out. Cut the tape free from the roll, do not pull it off until it breaks. Now wrap 4 turns in the opposite direction with light tension. Cut it free from the roll and do NOT apply any tension to the tape on the last turn. This way, residual tension in the tape will not pull the free end loose over time, avoiding "flagging." Using screw clamps or beefy cable ties pulled tight may run the risk of squashing coax cables enough over time to disturb their transmission characteristics. FORMING ROTATION LOOPS IN THE COAX You must allow the coax some extra slack to flex as your rotator moves the antennas back and forth. The first step is to set the rotator to the middle of its stroke, halfway between stops. If you rig your loop this way, it will only have to withstand half of the rotor's full stroke each way. Secure the cables to the mast below the bottom antenna. This can be done with tape, followed by gently snugged cable ties (for extra strain relief, since this is a stress point), covered with more tape to protect from UV. Wrap the coax/cables around the mast 2 times, forming a loose, 8 inch diameter spiral below the tape point. This can also be performed by loosening the mast in the rotor, and spinning the mast and antennas around. Don't pull these turns tight around the mast. They should have a diameter no smaller than recommended for the size coax you are using. Certainly not smaller that 8 inches in diameter for the RG-8/RG-213 sizes. The spiral of extra turns distributes the twisting along a longer section of cable, resulting in far less fatigue that the usual loop that just comes out sideways and back to the tower. If you have a tapered top tower, at this point, you can secure the coax/cables to the tower as above, starting from the top and going down. However, if you have a flat top tower, the top plate will have some rough edges that will tend to chafe the cables' jacketing. Bolt or clamp a short pipe to one of the tower legs that rises a few inches above the plate's edges. Begin attaching the cables to this riser and work your way down the tower. The riser will keep your cable spiral from catching on the top plate. MAINTAINING ANTENNA SWITCHBOX RELAYS The most likely problem here are the relay contacts. These may develop poor contact over time for a number of reasons. If you experience poor swr through a switch after testing with a dummy load, inspect and clean the relay contacts. CARE AND FEEDING OF RELAY CONTACTS NEVER ever ever use anything abrasive on a plated relay contact!!! The contacts are either gold flashed, or silver flashed, with various alloys added to modify the surface for different current requirements. If you remove even a few tenths of an inch (meaning ten-thousandths in plating slang) of surface, you'll absolutely destroy the alloy that keeps contact resistance low. The MOST you should ever use on a plated relay contact is something about as abrasive as cardboard. You can use a thin cardboard like off a matchbook cover soaked in toluene, xylene, or one of the other nasty solvents that evaporate without any residue to clean crud out of the contacts. Some have found that the paper in a dollar bill has about the right consistency for this task. This gentle cleaning does not apply to starter solenoids, or other hundred- ampere, non-plated contacts. They can be cleaned with a grinding wheel since they are not plated, but don't try that on gold or silver alloy flashed contacts typical in low or medium current relays. Relays get "dirty" for two main reasons: 1) They are not plated; 2) They have had the plating ruined by hot switching or "cleaning"; 3) They have debris trapped on the contacts; 4) They aren't in an application where they carry a required minimum current that "wipes" the contact. Number four is a major problem with amplifier relays. The receive contacts technically require a different alloy than transmitting contacts, because one carries virtually no current while the other carries several amperes. Since they are in one relay, you're stuck compromising. An antenna relay is the same. When they "get dirty", and they usually will because the material is a compromise, all they need is a VERY light wiping (like with cardboard) to remove surface contamination. Just be sure to blow any paper fibers out with air or freon when you are done, and NEVER coat the contacts with any "stuff". What type of relay is it that is the problem? Maybe it's the wrong type? Relays rated for hot switching higher currents, while impressing customers, make very poor antenna relays. They are great for starting motors, but not designed to maintain low contact resistance under conditions of low current flow. THRUST BEARINGS ROHN TB3 THRUST BEARING This bearing is engineered to be dry. Lubricating it will actually cause premature failure because the grease will hold onto any contaminants that are blown through in the wind (dust, rain, etc.). The same is true for crankup cables: do not use grease on them. If the bearing isn't turning freely, disassemble it and clean it as described below. If in doubt - throw it away and get a new one, they are relatively inexpensive. If you take a close look at your TB3, you will see a set screw inside which, when removed, allows the bearings to come out. There is really nothing that keeps this set screw in the right place. It could work its way in too far and cause the bearings to bind as they pass the end of the set screw. It could also work its way out too far (limited by running into the mast) such that a ball bearing can drop into the hole that is supposed to be filled by the set screw. The set screw is free to move within its threads for a few turns. There is an optimum place for that set screw to be and that is when it just fills the hole such that the bearings run smoothly past the end of it and there is no space for a single bearing to drop into. New TB3's have a punch mark on the threads to keep the set screw from moving too far. This is an easy way to keep it under control. Another easy way to keep it in place is to simply use grade blue thread- locking compound (removable) on it. Here is a step-by-step method for refurbishing a Rohn TB-3. This procedure is only intended to help improve the operation of a reasonably "healthy" unit. If you find serious problems, like cracked castings, broken or missing ball bearings, extreme wear, or cross-threaded screws - please do the wise thing and replace it with a brand new thrust bearing. Here's what you'll need: 1. A clear, well-ventilated, well-lighted workspace 2. A 16" x 24" or larger tin baking sheet with edges [so you don't lose the ball bearings] 3. A rag for cleaning 4. Mineral spirits for cleaning 5. 3/16" Allen key [preferably with a 6" handle and "rounded" end for insertion at an angle] 6. Miscellaneous filing tools [i.e. small hand files - round, flat; a Dremel tool with fine grinding capability] 7. Wrenches Procedure: 1. Remove all the bolts and nuts that secure the bearing to the tower and the mast into the bearing. 2. OVER THE BAKING TIN, CAREFULLY remove the Allen set screw located on the inside wall [where the mast goes through]. 3. The ball bearings will begin to fall out of the set screw hole. Rotate and lightly shake the bearing to coax the ball bearings out of the hole. 4. The unit was built with 32 [THIRTY TWO] ball bearings. Make sure you have them all! Set them aside. 5. Separate the top and bottom castings of the bearing. 6. Clean both castings and all the ball bearings with the rag and the mineral spirits or other grease-cutting cleanser. Note: It is normal for some dirt and metal powder to accumulate. The bearing should not contain grease. This unit is designed to run dry. 7. Inspect the ball bearing races. Look for unusually worn areas, pitting, cracks. Try rolling a ball bearing in suspect areas to see if it will get "hung". 8. Using your filing tools, smooth out any rough areas so the ball bearing can roll without resistance. 9. Do this for both castings. Note that your mast will be pushing down on the upper casting. This will cause the bearings to press against the top of the race in the upper casting, and against the bottom of the race in the lower casting. Pay close attention to these areas. 10. Make sure you look carefully at the area of the race in the upper casting near the set screw. Wear in this area will cause the thrust bearing to stick. 11. Insert the set screw - don't cross-thread it! Adjust it to the point where a ball bearing can run across it smoothly. Note, from the insertion side, how far the set screw is screwed in. Remove the screw and set it aside. 12. Reassemble the thrust bearing by holding the castings together and inserting the ball bearings back into the set screw hole one at a time. You'll have to rotate and jiggle the unit to find space for the last 5 or 6 ball bearings. Do this over your baking tin so that WHEN [not IF] you drop a ball bearing, it falls in the tin, not in the air conditioning vent. 13. Replace the set screw. Apply blue thread-locking compount to it and insert it until it is at the point you noted in Step 11. It should be roughly flush with the inside wall of the upper casting. Be careful not to cross-thread the set screw. 14. Now it's time to give the bearing a spin. It should run much smoother, and should not "stick" at all. 15. If you think the bearing could operate a little smoother, try adjusting the set screw in or out a bit. Remember, the ball bearings must go by the set screw smoothly. 16. If the unit still sticks . . . return to Step 2. If this is your second time through the process and you're still not satisfied - THROW IT AWAY and go shopping for a new one. INSPECTING YOUR TOWER INSPECTING NEW TOWER SECTIONS When picking up new tower sections from a dealer, inspect each section for defects before accepting them. Look for: 1) Bent or twisted sections (sight along their length). 2) Deformed or bent ends (6 places). 3) Mis-aligned joint sleeves on Rohn 45 & up (3 places). 4) Welds with cracks or multiple pinholes. 5) Gaps, flakes or separations in the galvanizing. 6) Missing assembly bolts. There should be a plastic tube containing the assembly bolts stuffed into the bottom of one leg. 7) For Rohn 25 only, to make sure you are not accidentally getting Rohn 20, verify the presence of 8 horizontal rungs, not 7. 8) Bent braces 9) Improperly drilled bolt holes. The holes should be oriented such that the bolt's axis points toward the geometric center of the tower cross- section. INSPECTING USED TOWER SECTIONS Take plenty of time to inspect every inch of used tower sections. Tiny defects may be hard to spot, but they could still seriously weaken the tower's structure and ability to carry stresses. Watch out for: 1) Bent or twisted sections (sight along their length). 2) Deformed leg ends that have been flattened out-of-round by over- tightening the joint bolts. Deformed ends may be accompanied by the presence of bent horizontal braces adjacent to each end of the section, where excessive jacking force was required to separate the sections. 3) Elongated or drilled-out bolt holes. 4) Cracks and splits anywhere on the 3 legs of each section. Hairline cracks caused by trapped, frozen water will be thin and run in the same direction as the leg. 5) Cracks or multiple pinholes in the welds (inspect every weld). These should be obvious without magnification. 6) Cut and spliced or bent braces. 7) Legs that you cannot see light through, that are clogged with debris. 8) Rust that is more than light, dusty surface rust. If there are flakes of rust and a scaly appearance of the metal, it is probably deep enough to weaken the leg. Use a flashlight to peer inside of each leg for interior rust. 9) Legs that have been repaired or welded to, other than the original factory brace and joint-sleeve (on R45 & up) welds. These welds are often easily identified by surface rust. ASSESSING BENDS IN TOWER LEGS If you run across a tower section that is bent, examine the metal closely. The structural integrity is compromised only if the leg section has become kinked or distorted out-of-round. The steel in the legs is ductile enough to let you correct minor bends without damaging the tubular shape. The biggest problem with a minor bend is that you'll have a heckuva time assembling sections involving a leg that is bent more than about a half an inch or so out of alignment. Champion Radio sells a good gadget for this called a Leg Aligner, which allows you to hook on to both ends of the mating leg sections and lever them into alignment. CORRECTING MINOR BENDS Here is one way to straighten a bent leg and maintain structural integrity. Slide a close-fitting pipe over the bent leg end and use the leverage to gently bend it back into alignment. Align the end of the pipe with the bent area to apply the corrective bend to the area that needs it. If it returns to its original shape and alignment with no trace of buckling, kinking, or other noticeable distortion (usually the case with small bends), you can be reasonably sure of it's original integrity. However, once a piece of metal has been bent many times, it can become weakened. If you see a leg that looks like it has been bent back to shape, but still has some residual curves (roller coaster shape) or a crack across it, pass it over for purchase. The tin is very ductile and should flow with minor bend correction. If a bend is severe enough to crack or flake the galvanizing, the leg is probably a goner per above distortion criteria. << 5) Cracks or multiple pinholes in the welds (inspect every weld). INSPECTION CHECKLIST FOR GUYED TOWER INSTALLATIONS Here are some mixed ideas/stories. Every Spring and Fall I inspect my towers and antennas thoroughly so that I can plan needed corrective work during the rest of the year. With high winds expected tomorrow and a beautiful warm sunny day today, I decided to begin my ritual inspection of my guy anchors, including guy wires, guy tension, turnbuckles and fasteners. Imagine my shock when I got to one of the guy anchors, and the guy wire was not there! This was one of my very few guy anchors that does not use a turnbuckle, this anchor rod has a "fist" style termination commonly used by utility companies. The "missing" guy was hanging down the tower, with the end on the ground near the tower base. This is a 1/4" EHS guy and all seven strands were fractured where they had passed thru the guy anchor, the three Crosby clips were still in place. The guy has now been repaired and re-attached. I have no idea why the EHS cable snapped where it passed thru the "fist"... This is the first time I've experienced a failure of a guy cable. Additional inspections planned this spring: Each tower base will be examined for evidence of rust or other deterioration and all accumulated dirt or other winter debris will be completely removed. Tower plumb will be checked from top to bottom with a transit and corrected by re-tensioning the guys if necessary. All tower ground wires and ground rods will be inspected. All RF and control cables fastened to sides of the tower will be inspected and fasteners replaced if there is any evidence of deterioration. Electrical connections to rotors and antennas will be inspected. All tower bolts and nuts will be visually inspected for tightness. This twice a year inspection routine has served me well over many years. I highly recommend that all tower owners follow a similar policy. During moderate to high winds, inspect your installation for any unusual movement, especially large or oscillating motions of a part that might cause fatigue in a metal part. Inspect cable clamps for looseness, and deformation or breakage of cable strands. Clear concrete bases above grade of any debris such as leaves and pine needles, that could retain water and hold it against your tower legs and base hardware. There is evidence of mechanical wear on the broken guy wire (shiny galvanize on either side of the break, loss of galvanize, loss of steel and some rust only on the strands in direct contact with the anchor). The break occurred on the part of the cable that took the heaviest load (midway around the "fist," directly opposite the direction of pull on the guy wire). Over a ten year period the guy must have gradually worn from moving in the anchor "fist"! After two or three strands wore partly thru, the remaining strands simply snapped! Thanx for encouraging me to look more closely at the damaged guy wire! Fortunately most of my guy cables are not fastened in this way (most use preformed grips and heavy duty thimbles). I'll very soon replace all of my remaining guy wires that have been installed this way for the last ten years In hind sight, its apparent that the closest Crosby clip must be close enough to the anchor to prevent the cable from moving in the anchor during high winds According to my 1994 Crosby catalog application information, the clip (cable clamp) should be installed "as near the loop or thimble as possible". Your annual tower inspection should include having a wire brush and can > of cold galv so you can fix any rusty spots as you find them Anchors At time of construction Volume and depth of concrete? Rebar present? Maintenance Deadman: Any visible corrosion, wear or damage? Spreader: Any visible corrosion, wear or damage? Are nuts and bolts tight? Turnbuckles: Any visible corrosion, wear or damage? Guy wire clamps or Preforms (Big Grips): Any visible corrosion, wear or damage? Safety Wire: Present? Any visible corrosion, wear or damage? Ground Rod: Necessary? Present? Bonded to metallic guys? Any visible corrosion, wear or damage? Guy Sets from the Ground: Any visible corrosion, wear or damage? Is all hardware present and not visibly loose? Any visible corrosion, wear or damage to guy wires, thimbles, and clamps (or Preforms/Big Grips)? Tower Base At time of construction: Height and depth? Rebar present? At time of each inspection: Any visible corrosion, wear or damage? Any sign that water has frozen inside the vertical tubes? Lightning Protection System and Safety Grounding Ground Rods: Any visible corrosion, wear or damage? Hardware tight? Meet NEC? Tower: Any visible corrosion, wear or damage? Is tower vertical and straight (i.e., not bowed)? Have all joints between sections been inspected? Guy Sets from the Tower: Any visible corrosion, wear or damage? Is all hardware present and not visibly loose? Any visible corrosion, wear or damage to guy wires, thimbles, and clamps (or Preforms/Big Grips)? Support Arms: Any visible corrosion, wear or damage? Is all hardware present and not visibly loose? Antennas: Any visible corrosion, wear or damage? Is all hardware present and not visibly loose? Cables and Electronics: Are cables attached to the tower at least every ten feet of travel? Notes on cures to items found: As with any outdoor building material, it is possible to discover items requiring maintenance. Where problems exist, cures are often obvious. For example: Loose nuts and bolts -- tighten Rusted nuts, bolts, clamps -- replace Rust on galvanized steel -- wire brush and cold galvanizing compound Frayed guy wires -- splice or replace Ground wire broken -- reground. There is virtually nothing that cannot be repaired or replaced on an amateur radio antenna support structure. . ASSEMBLING TOWER SECTIONS Break your tower installation task into the smallest bits that you can. When installing a guyed section, pull the guys up separately; not attached to the section. However, pre-installing guy attachments is a good idea, due to their complexity. When installing an antenna, do not bring up the coax attached - use a pigtail jumper from the feedpoint to the feedline. Use an antioxidant between nesting sections. Install bolts with the nuts on the inside of the tower to reduce the protrusion on the outside legs, which will snag your climbing lanyard, clothes, and skin (ouch!). PRE-ASSEMBLY ON THE GROUND This is one of the best things you can do to make a tower erection go smoothly. A little planning goes a long, long way in this department. Guy attachment points. Figure out ahead of time which section and rung your guys will attach to and install the guy bracket assemblies. Go ahead and install the outer bolts, connection links, and thimbles, too, but don't fully tighten all the bolts until after installation of the guys. If you are not using guy bracket assemblies (you should), mark the guy attachment points with tape. For the top section, it is a good idea, especially if you are raising lighter 25G, to pre-install your rotor plates and thrust bearings. Guy cables Break out your calculator and figure out how long each guy cable will be, then add 10 feet and pre-cut all the guys. Mark each guy with a tag identifying which guy it is for (top, mid, bottom, etc.) Pre-install the guy grips on one end of each cable, but only halfway. Wrap one side of the grip only, so that when you raise it up to the guy bracket, you can slip the free end of the grip through the thimble and link and finish the wrap in a flash while you're up on the tower. Top Section Pre-install your top-plate adaptor, rotor shelf, and secondary thrust bearing, if used. If possible, go ahead and install your rotor, assuming that your gin pole and haul line can take the weight. Check the balance point of the section and mark the appropriate rung with tape so that the ground crew will know where to connect. GIN POLES GIN POLE TYPES 1) Construction Plans: I built a gin pole which I have been using for a number of years. It is made from a 14.5 foot piece of 2" aluminum pipe (2" ID, 6063 alloy) and a rectangular aluminum plate, approximately 18" x 8" x 3/8". The pipe is held to the plate by two U-bolts, and the plate is mounted to a tower leg using two more U-bolts. A hole is drilled through the top of the pipe for an eye bolt which holds the pulley. It's simple to use, although not quite as convenient as the Rohn ginpole. I've used it on Rohn 25 and several crankup towers. To be useful on a crankup tower, you need to have several inches of offset between the pipe and the tower legs so the pipe clears the bottom tower sections when the tower is nested. Total cost of the plate and pipe from an aluminum supply shop was about $75. Now some info on addresses, pricing, and the like: 1. IIX Equipment Ltd. 4421 W. 87th St Hometown, IL 60456 (708)423-0605 e-mail iix@interaccess.com Fax (708)423-1691 $189.95 for a kit that includes gin pole head and mounting bracket only. (pole itself is not supplied). Unfortunately, this kit uses a flat pulley sheave, and should be upgraded to a grooved/cupped sheave for reduced friction. 2. WB0W, Inc. 1210 Midyett Road Saint Joseph, MO 64506-2407 (800)626-0834 Fax (816)364-2619 e-mail wb0w@ibm.net The WB0W GIN POLE can now be ordered with a V pulley for cable, or cupped pulley, or the standard flat pulley for rope. Unfortunately, the flat pulley allows the rope to rub on the side of the pulley body. Using maybe 3/4" hemp line would probably be OK, but it may not work well with small synthetic line. You should definitely order the cupped pulley for ropes. 3. Antenna Mart/Max Gain Systems 221 greencrest Ct, Marietta, GA, 30068 770-973-6251 Part # AMQ-SGP-2 Price: $347.50 + S&H email: mgs@avana.net web: http://www.mgs4u.com Two piece design, will ship via UPS. Easy to transport Length approximately 12 ft. 6 in. Weight 36 lbs. Shipping weight 40 lbs. Special, large lathe turned rope pully. Heavy duty design. Mounts and unmounts in seconds. Uses up to 7/8" rope or 3/4" aircraft cable. Machined pully is high impact plastic. Aluminum pully is $10.00 extra cost option. HOMEBREW GIN POLE MAST Here's how I made my own gin pole mast with just a little machine work with hand tools at home. I wanted a 12-foot long, two-piece unit so I could pack it inside my car or van. I bought five, 6-foot long sections of aluminum pipe from Texas Towers in the following sizes: 6061-T6 EXTRUDED TUBING: 2.0" OD, 1.760" ID, 0.120 wall, 6' long, qty 2 6061-T6 DRAWN TUBING: 1.750" OD, 1.634" ID, 0.058 wall, 6' long, qty 1 1.625" OD, 1.509" ID, 0.058 wall, 6' long, qty 1 1.500" OD, 1.384" ID, 0.058 wall, 6' long, qty 1 These are all conveniently UPS shippable and inexpensive! Notice that these sizes all telescope closely, one inside the other. I nested the three drawn sizes together and carefully aligned one end. Then, with one saw cut, I cut a 16" long section from the group, and carefully filed the ends square and flush with each other, effectively creating a 16" long coupling that is 1.750" OD and 1.384" ID. Using a handheld de-burring tool (see Home Depot), I very thoroughly radiused the inside edges of each end of the coupling, so that the haul rope would pass through it very easily without snagging. The sections fit so closely together that they appear to be one piece. I placed the coupling 1/2 way (8") into one of the 2" OD extruded pieces and clamped the works in a vise. Next, I drilled, tapped and countersunk four holes to accept #10, flat head countersunk machine screws. I placed 2 of the screws approximately 3 and 6 inches away from the end of the mast half (where the joint will be), and the other two in the same spacing but 180 degrees from the first two. I trimmed the screws for length such that when they were fully seated, flush with the outside, the ends are just flush with the inside of the coupling and do not extend into the rope path. I applied a thread sealant (Loctite blue) to these four screws before final installation so that the coupling will stay permanently attached to one side of the two-piece mast. Next, I slipped the remaining mast half over the coupling and prepared four more screws and holes. I did not seal this second set, since this will be the side of the joint that comes apart. Since I drilled all the holes by hand and eye, I punched index marks where the two mast halves meet at the joint so that I could always mate the screw holes. The joint is surprisingly tight and there is no noticeable play on the resulting, 12' mast. It's real handy to be able to break it down into 6' sections for storage. The screws fit flush on the OD of the mast, allowing it to slide through the gin pole's clamp assembly nicely. GIN POLE ROPE The general consensus is to use a braided, 3/4" Dacron rope, if you can afford it. A braided rope, rather than a twisted type, avoids the unwind/wind cycles that occur under load. Braided rope is also far easier to coil. Dacron rope is generally considered the best, but it is the most expensive. Nylon is more readily available in the home stores, but it stretches quite a bit, reducing your control of lifted objects. However, this stretching helps reduce shock loading if items are dropped. Larger sizes, such as 5/8 and 3/4, although far stronger than necessary to do most jobs, are much easier to grip. 5/16" is the smallest size you would want to use, and has plenty of strength (around 1200 lb for braided Dacron). The length you need will be approximately twice your tower height plus an appropriate length (at least 50 feet) for the ground crew to use while maintaining a safe distance away from the bottom of the tower. For a 100 foot tower, then, your rope should be at least 250 feet long. The easiest way to store this rope is inside a tall, round trash can. The rope can simply be fed into the can without coiling and will come out readily without tangling. Smaller ropes may also fit very nicely into a plastic 5-gallon bucket. Pick up one of those plastic seat lids that fits on the bucket and you have a nice carrying case for your rope. RIGGING THE GIN POLE AND TURNING BLOCK Be sure to use a turning block at the base of the tower to keep the haul line lined up with the axis of your gin pole and to prevent side loads. Your turning block *must* lock onto the tower with a safety hook and catch, a locking carabiner, or a screw link. DO NOT CUT CORNERS HERE! Don't play around with hooks that don't have safety latches. Nothing will cause a disaster faster than having your turning block break loose in the middle of a lift! The turning block should have a pulley sheave diameter of at least 2" for best operation, and a safe working load (SWL) at least equal to the heaviest load you want to lift. Again, keep in mind that the safe working load of an item is usually only 20% of its breaking strength or less. The position you select for the turning block will determine which leg the gin pole will have to be mounted to keep the rope lined up. If there is a particular side of the tower you want to lift items on, place the turning block closest to the desired leg in that direction. When you mount the gin pole, mount it on the leg that places it as close as possible to directly above the turning block to reduce rope friction. It is imperative that the haul line remain free when manipulating items up and down during placement. Keep the mast of the gin pole retracted, if possible, while repositioning it for best control. Mount it as high as possible on the tower leg such that it is directly above the turning block at the base of the tower. When extending the gin pole, turn the pulley out so that it faces away from the tower to reduce the friction during the long hauling stage of each lift. Only at the end of the lift do you swing the item over the tower, causing the rope to wrap somewhat around the gin pole. GIN POLE KEEPER LOOP A `keeper loop' is a handy way to speed up rigging and de-rigging the haul rope in your gin pole. The `keeper loop' is simply a length of small rope that is long enough to go through the gin pole and back around to itself. Tie the ends together to form a loop. When you need to thread the gin pole with your haul line, untie the keeper loop, and tie one end to the free end of your haul line. Use the keeper loop line to pull your haul line through the gin pole. Stow the keeper line during gin pole use. When you are ready to de-rig the pole, reverse the process, pulling the keeper line back into the pole for storage. RAISING MASTS When raising very long masts, you can tape the top of the mast to the haul rope to stabilize it and keep it vertical while you are raising it. When the mast reaches the top, you cut the tape as it passes by you. Another technique is to have the pick point on the mast above the midpoint; then it goes up vertically (up-side down) with no problem. What you do at the top of the tower when the haul line knot hits the top of the gin pole is to flip the mast 180 degrees. Since you've got it captured at the gin pole, it will just rotate until you have the short end in your hand (a short rope attached to the 'top' will allow you to pull it down to you). Then you just lower it through the thrust bearing/tower top. This produces the maximum 'pucker factor' when dealing with masts but it does work well. It actually is easier than it sounds. CLIMBING MASTS Of course you want to make sure that the mast is safe to support a person on it, such as a chromoly mast, secured at the bottom with dual thrust bearings, or one thrust bearing at the top of the tower and the rotor at the bottom of the mast. MAKE SURE that the mast is not just a piece of thin wall something or other. It's a pretty good-sized mental adjustment to be able to climb a mast but remember the load is all vertical and the tower is capable of handling big loads. Compared to big wind stresses, one 200 pound climber isn't going to make much of an impact on the installation. You can make temporary steps to use with your tower working tools and equipment. Use 2" channel iron 15" or 16" long. (Channel is more secure than angle.) Cut "V" notches in both flanges to match your mast diameter but don't cut all of the way to the flat part. Drill holes for two U-bolts (second one is for safety). Cut along the flange bend about 3/4" from each end on the top flange only and bend the ends of the flange (about a half inch) up 90 degrees (keeps your foot from sliding off of the end of the step). Take a cold chisel and using the corner, beat a huge number of indentations into the top surface of the step to make it less slippery. Try raising ridges of steel by increasing the angle of the chisel. Buy the U-bolts just long enough to pass through the step or cut off the excess so your cloths don't catch on the ends of the bolts. You're all set, except for the courage. Mount the first one a foot or so above the last spot that you can stand on. Put another one (if required) a foot or so above that. Now you've got a temporary ladder to get you up the mast. While most people wrap their belt around the mast a couple of times to secure themselves, a good tip is to have a separate short lanyard (about 2 feet long) that is just used for mast work (tnx to K6NA for this tip). RAISING ANTENNAS CHECKING ANTENNA TUNING BEFORE RAISING Don't fall into the trap of assuming that a brand new antenna that you have just assembled, even though the manufacturer's literature may say that no tuning is required, will have a satisfactory SWR curve. Consider checking side-mounted antennas on their mounts at a temporary location near the bottom of the tower, so you can easily tweak them when they are interacting with the nearby tower. Here is another point to consider. There is a tendency of HF beam elements (especially the longer ones) to couple with the earth when they are close to ground, making their frequencies of best resonance lower that when it is raised in the air. If possible raise the antenna 20-40' in the air using a non-conductive tram line or other overhead line that you can rig. Try lashing the antenna to a 20 foot extension ladder with a temporary mast and stand the assembly up with some friends while checking the SWR using a temporary pigtail extension for the feedline. If you perform your tuning close to the ground, the best resonance frequency may rise higher than you wanted once the antenna is installed on the tower. Plan ahead to check this before or during the installation process before all your ham friends call it a day and start digging into your beer, barbeque, and doughnuts! TRAMMING Tramming is the best way to raise a large or bulky beam assembly to the top of the tower. A 1/8" steel cable is installed from the ground, up to a point on the mast above the attachment point, usually through a temporary pulley, and then back down to ground directly opposite of the originating point to provide a balanced stay. A traveling pulley attached to one side of this tram wire carries the antenna suspended below it up the wire directly to the mast. Attach the pulling line to a short piece of pipe attached to the antenna boom. This pipe will stay pointed at the mast, parallel with the tram line, as the antenna rises, keeping it properly oriented with the boom perpendicular to the tram line. A second pulley can be added at the end of the pull pipe for even more stability. If a rope is used for the tram line instead of a cable, the antenna can be tested before permanent mounting by pulling it only part way up in the air with a temporary feedline. It can be quickly lowered again to fix any swr problems before permanent mounting. Using powered machinery to raise antennas should be avoided unless the operator has absolute control over the hoisting device and has direct communication with someone on the tower who is watching the assembly raise up. REMOVABLE TAG LINES The antenna tag line ends have to be reachable from the tower. Use a clove hitch to secure them to the boom. Then take them out to a convenient element and then wrap them around the element 2 or 3 times to provide a little friction for the rope. (BTW, two tag lines, one on each side of the boom, is handy.) Finally, tape the tag line to the element out far enough so that you won't bend the element by pulling on the tag line but enough that you can get some leverage while pulling on the rope. After applying the tape (2 or 3 wraps of electrical tape is usually fine), work the tag line back and forth a couple of times pulling it through the tape to loosen up the grip a little. After the antenna is up at the top of the tower but before it's clamped to the mast, you untie the clove hitch on the boom, making sure that there are no knots in the line. Next you have your ground guy start pulling the tag line. He'll be pulling it through the tape and when you get to the end, have the ground guy give a little extra pull as you launch the end of the rope in the direction of the tape. As he pulls, it'll slide through the tape and fall to the ground. All that's left is a piece of tape that'll probably fall off in a couple of years and a successful antenna installation. ALIGNING BEAMS Finding true north In principle, north can be located by using a magnetic compass and making an appropriate correction. Magnetic north is substantially off from true north -- the exact amount varies by location. But there are better ways. Polaris, the north star, can be used, but this is inconvenient -- you have to wait for a clear night -- and not entirely accurate either. The most accurate way to find a true north south orientation is by using the sun itself to find the direction of a shadow cast by a vertical object when the sun is at its zenith. This is easier than it sounds, and can be done by measuring the length of the shadow cast by the upright before and after noon. Set up a vertical pole (or use a rope with a weight) to cast a shadow on the ground. If you use a rope you will need to make the reference point somewhere near the top to cast a visible shadow -- like a stick knotted into the rope. The base of the shadow will be the first point for your south-north axis and the reference point or top of the pole will trace the second point. At some time in the morning, mark the spot on the ground where the reference point casts its shadow. Measure the length from the base to the end of the shadow, and using a string of that length, trace out a semi-circle on the ground with the base of the shadow as its center point. As the sun rises higher in the sky, the shadow will first shorten as noon approaches, and then will lengthen. At some point in the afternoon it will reach the semi-circle you traced in the morning. Note the spot when it crosses the arc the second time. The midway point between the morning and afternoon points, will be directly north of the base point of vertical object." Here's a simplified version of this scheme. Look up the sunrise and sunset times in the newspaper for the day. Calculate the time that is exactly halfway (the "transit time") between them. All shadows will point true north at this time. There is a website you can visit that will calculate the transit time for you for any date and location. You will need to know your local longitude and latitude. Visit http://aa.usno.navy.mil/AA/data/docs/RS_OneDay.html to obtain the transit time. MINIMIZING ANTENNA INTERACTION Turning 2 beams that are stacked vertically such that one beam is pointed 90 degrees from the other minimizes interaction. This 90 degree misalignment is compensated for when aiming that particular beam. CHILD PROOFING A TOWER/ANTI-CLIMB GUARDS ANTI CLIMB DOCUMENTATION If you live in a neighborhood where there may be a likelihood of kids playing on or around your tower, you may want to consider some anti climb panels on the bottom section to block access to the tower rungs. A warning placard would also be appropriate. Photograph the installation to document it for future legal concerns. METHODS One way to keep people from climbing your tower (especially kids) is to build a cover for the base. Just take a sheet of marine grade plywood. Cut to fit on 2 sides. Notch a 2 x 4 for backing and drill, install carriage bolts and washers. The 3rd side cut to fit and hinge it to one of the other sides, At least 3 hinges, drill and use carriage bolts and washer. washers and nuts on inside all three sheets, Take a hasp and install on the other side and padlock it. Paint it and will last for 20 years. When you climb, unlock, swing open, and climb. Then when you come down, swing back and padlock. Another way is to use standard galvanized hardware mesh. It wraps around Rohn 25 nicely, and you can lace it with some galvanized wire. To climb the tower, put a 6 foot step ladder up against the side to get above the mesh. This method is much cheaper than the Rohn flat metal guards, and it is probably as effective. Anti-climb methods will prevent kids and pranksters from climbing, but someone who is dead set on climbing is going to find a way around your efforts. After you make your anti-climb sections, take a few photos of them as installed and file them away so you'll have them if anything ever happens, and you need to show the court how you made a reasonable attempt to prevent unauthorized climbing. TOWER STRENGTH INFORMATION >Does anyone know what safety factor Rohn uses for 25G, 45G and 55G? Can >you refer me to the drawing or page that says it? First a word about the weight of each type. For each 10-ft section, the weights are: 25G-40 lb, 45G-70 lb, 55G-90 lb. Sorry, but the safety factor is not 3:1. I wish it was. The EIA-222 standard requires a 2:1 safety factor on the guy wires. I have done comparison calculations and I come up with about the same thing they have in their literature. Everyone should do a sanity check calculation like this to make sure they are doing it right. The tower buckling load has a safety factor on it that varies with height. As an example, drawing CB70488 R1 shows a 190' tower in a 90 mph wind zone. The base load for this tower is 9,870 lbs. The same drawing shows the base load for the 70' tower at 3,010 lbs. Now this is the same section of tower but the applied load is different while the guy spacing is almost the same (31' vs. 32'). So I guess you could say that it has a 3:1 or better in this particular case. In both cases the limiting factor is the guy strength available in the top 3/16" guy wire. Now if you would use 1/4" guy wire (6700#) versus 3/16" guy wire (4000#) on a 70' tower, you won't get anywhere near the 9,870 lbs of base load so you won't over load the tower section, but you should be able to get about 60% increase in antenna wind load available. This is provided the guy anchors don't pull out of the ground and you use the GA25GD guy bracket to get the load properly distributed into the tower - especially for the top guy. The second set can still be 3/16" and looped around a tower leg. The Rohn catalog contains drawings for each type of tower section that list engineering properties. For quick reference here are some facts for Rohn 25: The maximum allowable bending moment on a section of Rohn 25 is 7,000 foot- pounds. The compression strength of Rohn 25 is 8430 lb. per leg, or 25,290 lb. total compression at the bottom of the tower. CALCULATING WIND LOAD AREA and WIND LOAD WIND SPEED ZONE First, determine the maximum design wind speed for your tower. The industry standard is contained in the TIA-222-e specification. The EIA/TIA-222E wind Map is available at: http://www.skyenet.net/pirod/wszmap.htm. CALCULATION METHOD I want to calculate the effective wind area of a 2" diameter mast that is 72" long. Therefore 72" X 2" = 144 sq.in = 1 sq.ft. The calculation above would be accurate if the mast were square. But because it's round isn't there a constant I need to multiply the result by. You're just about there. The round-member multiplier, or drag coefficient, is 0.67. It is used by Dave Leeson, W6QHS, in his book "Physical Design of Yagi Antennas", page 7-6. One caution when using this factor to reduce the area of round members. I noticed that there are TWO figures for wind loading capability in the current Rohn Catalog shown on the guying charts. One figure is for flat members and the other figure, a larger one, is shown for round members. So I think Rohn is already taking the shape of the antenna load into consideration in publishing two numbers for wind loading. I think it would be incorrect for you to use Rohn's wind loading number for round members and then also reduce the area of your antenna and mast by 2/3. I believe this amounts to using the same factor twice when it should only be used once. Years ago the "conventional wisdom" said that one should combine element and boom areas according to the Pythagoreum theory to obtain a net effective area (if you payed attention in Trig class it uses the A^2 = B^2 + C^2 formula). This has since been proven wrong. The maximum effective area of any antenna is simply the largest of either the elements or the boom. When calculating forces, the shape factor is the number that you are looking for. For round members, the shape factor is 1.0. For a flat surface the shape factor is 1.6. This all factors into the equation: Load in Lbs. = 0.00256 x (V mph)**2 x Shape Factor x Projected Area. This is from Section 25 of the National Electrical Safety Code, ANSI C2-1997. (The bible of electric utilities). This section has its roots in the UBC regarding wind loads. It also contains some nifty parts about calculating the wind load on a lattice work tower and some caveats regarding the use of extreme wind loading. From: "Match Your Antenna To Your Tower", Roger a, Cox, WB0DGF (Telex/HyGain), HAM RADIO, June, 1984..... F = PA, where F is wind force in pounds, P is the wind pressure in lb./ft^2, and a is the antenna wind area in ft.^2 P = 0.004 V^2, for FLAT SURFACES where V is wind velocity in MPH P = 0.004 (0.667) V^2 for ROUND surfaces, where 0.666 is the shape factor Examples: At 80 MPH, P = 25.6 lb./sq. ft. (Flat) At 100 MPH, P = 40 lb./sq. ft. (Flat) for a 10 sq. ft. antenna, F = 256 lb. @ 80 MPH, and 400 lb. @ 100 MPH (flat)etc. Note: The equation P = 0.004 V^2 accounts for gusts and turbulence; for steady laminar flow, P = 0.00256 V^2 should be used. Although the formula P = 0.004 V^2 is nice and simple, and was used for years, there are newer formulas used by EIA-222-D (effective June 1, 1987) and the -E version (if I can find my copy of it in the stack somewhere). 2.3.10 The design wind load (Fc) on a discrete appurtenance such as an ice shield, platform, etc (excluding solid microwave antennas/reflectors) shall be calculated from the equation: Fc = qz Gh Ca Ac (lb) [N] qz is the velocity pressure, calculated based on the centerline height of the appurtenance, qz = .00256 Kz V^2 (lb/ft^2), where Kz = [z/33]^(2/7) for z in ft. V is in mph. z is the height above average ground in ft. to midpoint of section. Kz is the exposure coefficient. Gh is the gust response factor, calculated based on the total height of the structure, Gh = .65 + .60/(h/33) ^(1/7) for h in ft, 1.00 <= Gh <= 1.25. Ca is the force coefficient applied to the projected area (ft^2) of a discrete appurtenance (Ac). If the aspect ratio <= 7 (member length/member width), then a cylindrical shape has Ca = 0.8. If the aspect ratio >= 7, then Ca = 1.2. For flat members, use 1.4 or 2.0. Ac is the projected area of the appurtenance in ft^2. As you can see, it is much more complex now. I still like the old formula best. There really isn't any difference in the formula for wind load for appurtenances (antennas). The main difference is in Table 3, Appurtenance Force Coefficients. For an aspect ratio <= 7, Ca = 0.8 for cylinders. For an aspect ratio >= 25, Ca = 1.2. For ratios in-between, use linear interpolation. If I read this right, most HF antennas would fall into the Ca = 1.2 category. This is dramatically different from the old 2/3 shape factor! The effective area spec on our antennas already have this 2/3 shape factor built in, so you might want to multiply by 3/2 to get the projected area. Other manufacturers may do this differently. The most accurate method is to find the maximum PROJECTED antenna area (either the boom or the elements only) AND use the EIA-222-E formulas. NEWER CALCULATION METHODS Basics: All antenna area calculations start with the simple determination of the projected areas of the antenna components. The projected area is calculated by multiplying the length x width. A piece of tubing that is 2" dia x 24" long has a projected area of 48 SqIn. Next, all of the pieces in a specific component of the antenna (like an element or boom) are added up to get the total. Usually, the total is divided by 144 to get the area in SqFt. Then the element areas are added up to get the total elements area when the wind is parallel to the boom. The boom area applies to when the wind is parallel to the elements. So, we have the flat projected area of the antenna at two azimuth angles, 0 & 90 degrees.What happens after this is what can cause confusion. Problems: Effective area Methods: Back in 1992, when I wrote the 1st version of YagiStress, there was a popular concept that said the maximum antenna area could be found by solving the Pythagorean equality (A^2 + B^2 = C^2) using the total element and total boom areas. Max area = (Boom area^2 + Element area^2)^.5 This always produced a value that was larger than either of the two areas and it occurred at azimuth angles near 45 Deg. I'm pretty sure that Hygain and Force 12 were using this method to generate their spec's. Leeson (W6QHS now W6NL) and I were also using it. I was never able to figure out what the others were doing. Drag Coefficients: All recognized standards, for analyzing structures subject to wind loading, allow for the application of a drag coefficient to account for the shape of the structural members. This is often referred to as a "shape factor". EIA- 222-C (1976) used .666, EIA-222-D (1986) used 1.2, UBC (1988) used .8. All of the factors reduce the flat projected areas by some amount to arrive at the "Effective Area" for an antenna using round members. I think that some Mfgr spec's used this reduction and others may have not. It is very clear that the spec's did not describe what the value represented. Some manufacturers, in other publications clarified their calculations. Confusion: It was never very clear in my mind what the numbers represented. In some cases it was clearer than others, but trying to make intelligent comparisons was impossible. Now, maybe I was the only one who was confused. I'm sure most people thought the areas were derived in the same fashion and could be compared. I am convinced that this was not true. New Methods: In the Spring 1993 issue of Communications Quarterly, Dick Weber, K5IU, published a paper describing wind flow over cylinders at various wind attack angles. The methods described resulted in very different values from what many of us were getting. Leeson and myself independently made some test antennas and separately arrived at the conclusion that the Weber method was correct. I know that Roger Cox at Hygain, and Tom Schiller at Force 12 also picked up on it. I have no direct knowledge about the others. Leeson changed his spreadsheets, but couldn't change his book. I made the changes for YS 2.0 Here are the changes that come out of the new method, it's termed "The Cross Flow Principle" by Weber, or the "Sin^2 behavior of Cylinders in Yaw," by Leeson: The wind flow over the cylinders results only in loads that are perpendicular to the axis of the cylinder. This means that all element loads result in forces along the boom axis. Asymmetric element placement along the boom does not result in a wind torque imbalance. This makes the Leeson element torque compensator unnecessary and ineffective. The Max Projected Area of a Yagi is the largest value determined for the boom or the elements. If the boom area is larger than the total for the elements, the boom area is the max area. The minimum is somewhere in between 0-90 deg azimuth. The min area angle is determined by the ratio of the elements to boom area. If the boom and elements areas are equal the minimum area occurs at 45 deg. What do users need from an antenna area Spec.? I define a user as one who will use the information to evaluate it and make decisions, or a designer who will use the info to determine loads on a structure. The first thing most recipients of a specification do, is make an attempt to compare the area values to other spec's to determine which is "best" or which best suits their application. The second thing a user might do with the area value is design, or have his installation designed. In the U.S., some municipalities require UBC compliance, others require EIA. I'd guess that differences exist in Europe also. If the antenna area values are " flat projected areas", it is clear what the values means and the designer can proceed with applying the appropriate shape factor and wind pressures according to the code. If the areas have been already factored, and the spec doesn't tell what was done, the information is useless. It actually can be dangerous, if the designer is forced to guess what the value means! The third thing a user might attempt to do with the information is select a rotator. Efforts to match antennas and rotators, based on area alone, are useless. That is another discussion for another day. Suggestion for a Standard Antenna Area measurement: Manufacturers should calculate the flat projected areas of the antenna at 0 Degrees & 90 Degrees azimuth, and present them as such. That's it! The user can decide what shape factors and wind loads to apply for determining loads on the mast and tower. It is important to list both values. Some antennas have more area at 0 Deg, others more at 90 Deg. Example: Most 20 meter yagi's with 4+ elements have more element area than boom area. 10 & 15 meter yagi's tend to have more boom than element area. This assumes that the designer has tried to minimize area. We need both 0 & 90 Deg areas to determine the loads on a mast or rotating tower. The max loads will usually occur at either of the two angles, unless we're lucky enough to get them equal at both. Another antenna property that we need, but has not been a consistent part of the antenna spec's is antenna torque. There is only one generic value, for Mfgr's to define here. It is the torque developed when the boom is broadside to the wind. This is caused by either placing the mast connection away from the center of the boom. Or, coax and balun loads that will cause an imbalance. There is another (usually small) antenna torque developed by the connection to the mast (or tower), when the antenna is pointed into the wind. If we mount the antenna to a 2" Dia or other common size mast, the Mfgr can provide this torque value. Since, the Mfgr has no control over how we will mount the antenna to a tower sidemount or TIC ring., he can't determine what this value is. That's our job! Just getting the torque value for the wind broadside to the boom case would be a great improvement! It might make some Mfgr's stop trying to attach the mast to an antenna at the weight balance point, which is usually not at the zero wind torque location. At the very least, providing this value, would allow us to understand why some antennas are "Wind Vanes!," and avoid them, unless we plan to overpower the problem with more robust rotator! The equation used in TIA/EIA 222-F which is the latest revision and the UBC defines the basic wind speed stagnation pressure (a datum) value as: Qs = 0.00256V*V This is base on Bernoulli's equation which can be arranged to give: Qs=1/2*RHOair*V*V8 Density(air) at 59 deg F and 29.92 in Hg is 0.0765 lbs/cf Rho=Density/g: RHOair=.0765/32.2 To express in MPH Qs=1/2(.0765/32.2)(1/3600)*(1/3600)(5280/1)*(5280/1)*V*V Qs= 0.00256*V*VI don't know of any safety factor in this. Hank / KR7X Previous references to the older EIA 222 Rev C spec. stated the formula in that spec was .004V^2.Here is why it is different. The Rev C spec included a built in 30% increase for wind gusts. If we start with the fundamental .00256V^2 and add the 30% increase in wind speed we get a 69% increase in windload. If we multiply the original formula by 1.69 we end up with .004V^2. That's where that formula came from. ANOTHER TAKE ON EFFECTIVE PROJECTED AREA Here is one way of finding "EPA". There are a number of variations and interpretations that can be used to arrive at slightly different answers. Calculating EPA is an art form and is subject to one's own style and taste. The end result should be within 10% to be called "close enough." Let's define some terms: PA - Projected Area - length x width. FPA - Flat Plate Area: converts round areas to flat areas by multiplying PA times .67 EPA - Effective projected area: The projected area (PA) times the shape factor. (PA x Ca). The term Ca varies with the shape (round, flat, other) and the length to width ratio. Ca - shape factor of appurtenance. For rounds, Ca varies between .8 and 1.2 for L/W = 7 to 25 respectively. For flats, varies from 1.4 to 2.0 for L/W = 7 to 25 respectively. Where did the confusion on EPA, FPA and PA come from? The EIA-222 specification has had various revisions, resulting in a proliferation of methods. For Rev C, the world used FPA, and when Rev D came out, the procedures were changed to EPA. Many antenna manufacturers have still not updated their catalogs. They may not like the larger EPA numbers or they may have limited manpower. There are a lot of antenna manufacturers and many of them use different values and don't say which method they are using. The EIA-222-F (current version) spec says that if the antenna is made up of rounds, you can conservatively multiply FPA by 1.8 to get EPA. One of the best methods that some antenna manufacturers publish is the thrust value (T) and the wind speed (V). To get EPA = T/(.00256 x V x V) (I can't do the squared thing in plain text) Now the problem gets worse, because almost none of the antenna manufacturers publish information on their antennas with "ICE" and ice controls the design of guyed towers (but it is "optional" whether or not to design for ice and how much ice). The majority of commercial towers are designed for 1/2" radial ice with 75% of the basic wind speed wind pressure. So the trick is to figure out which is the value given in: PA, FPA, or EPA. This is mainly done by looking at the antenna and determining the length and width of each antenna element and find its Ca x PA. The total of all elements is the EPA. For ice, you can repeat the process by adding 1" (for 1/2" radial ice) to all lengths & widths. Or for a quick approximation, if the antenna is made up of many different diameters, take the (EPA/1.2) and divide it by the total length of all the round elements. This will give the average diameter. Then EPA(1/2") = (D+1") x (L +1") x 1.2 REFURBISHING USED TOWER TOUCHING UP RUST SPOTS As long as the tower sections are not corroded to the point where their physical integrity is suspect, surface rust spots and new, bare steel parts can be touched up and fresh, protective galvanizing coating applied with a zinc-bearing paint commonly referred to as cold galvanizing compound. Prep the surface by wire brushing, followed by a scrub with a piece of 3M scotchbrite and clear table vinegar. After drying, paint on the cold galvanizing compound. This paint should contain 90% or more zinc, and the good stuff will weigh about 25 pounds/gallon, 6.5 pounds/quart. It will also be expensive, up to $20-30 or so per quart, $60-80 per gallon. Some good brands are Klein, LPS (cold galvanize), ZRC (Galvilite, www.zrcworldwide.com ), Sherwin Williams (Zinc Clad #5), Rust-Oleum (#2185) and DAP (galv-a-grip). LPS also makes an excellent spray-on cold galvanizing product, although spraying makes less efficient use of the product on the round tower members than flat plates. SEPARATING OLD TOWER SECTIONS I bought an automobile scissors jack at a garage sale and modified it by having my neighbor weld some small steel angle pieces on the top and bottom of it such that when I expand it inside of either 45 or 25 tower, it allows me to easily separate them. I also had him weld a small bar on the jack where the handle used to be inserted so I can easily hand crank it on the tower. He also welded a short length of chain with a clip on the end of it for attaching it to the tower so I won't drop it one someone's head below. A tip for using this jack: Insert it in the tower and crank it up against the tower section horizontal cross braces. With all the bolts removed from the section you are taking down, reach up a couple of feet and vigorously jerk the tower leg back and forth several inches. The tower legs should separate a little. Tighten the jack again and shake some more. Continue this until the sections separate. ADAPTING CATV HARDLINE for AMATEUR USE CHOOSING LENGTH If you make your CATV aluminum sheathed coax 224.5 feet long it will act like a linear transformer and if you feed it with 50 ohms, you will get 50 ohms out of it at the other end on the frequencies listed above. The minor difference between 1.775 and 1.8-2.0 MHz is minuscule and it will be great for all the other bands!!!! Dunno about WARC. Haven't done any calculations for them. The velocity factor of CATV foam filled aluminum exterior coax is 0.81. The velocity factor for some air-dielectric types is 0.91. For foam dielectric, if you want it to be half waves or multiples there of at 1.775, 3.550, 7.100, 14.200, 21.300, and 28.400 MHz, use the formula: 984/1.775 X .81 and it will give you the answer of 554.366 feet. That is the length of a full wave length at 1.775 MHz. Half that for a halfwave and you get 277.183 feet. Multiply that by the velocity factor of the coax (.81) and you get 277.183 X .81 = 224.5 feet! HARDLINE CONNECTORS FOR AMATEUR USE Now for the next problem: connectors. AD4KT Charlie Davis, Woodland Creek Antennas in Jefferson, GA ,manufactures PL259 coax plugs for 1/2 and 3/4 inch hardline. He is a physicist at the Univ of GA. His price is about $8 for the 1/2 inch and $13 for the 3/4 inch. These are very nice product for CATV hardline and I have one in my hand. His connectors are the appropriate size brass compression copper tubing fitting machined to fit the PL259. Solder the center conductor, apply Pentrox to aluminium /brass surface contact area, tighten the compression fitting and you are done! You may contact Charlie at 706-367- 8069, cdavis@hal.physast.uga.edu 11 Old Pendergrass Rd., Jefferson, GA 30540 Another source for hardline connectors: DAVIS RF Co., Commercial wire/cable, RF connectors, custom cable and connector design. Discounts to hams. Visit their web site at www.davisRF.com. 1-800-328-4773 (1-800-DAVIS RF) POC: Steve Davis, K1PEK If you want to home brew: Go to your local Lowes Store (or Home Depot or whatever) and look for a 1/2" to 3/8" pipe coupling. It is made by Anderson-Barrows. Its Anderson-Barrows designation is U50. The description on the outside of the package says: Tubing to Female Pipe Coupling, Part No. BP966-P, 1/2" x 3/8" Remove the inner (loose) tubing and discard it. Place the sleeve end over the 1/2" aluminum tube and move it back a ways. Take a pipe cutter and cut the aluminum at 7/8" back from the end and then (by taking a utility knife and cutting through the shield along the axis of the coax, using care to not cut oneself) remove the 7/8" aluminum shield and cut away the foam from the center conductor while being careful to not scrape off the copper plating of the center conductor. When you have accomplished that, you are ready for the next part. Now take the previously-obtained Amphenol barrel connector (designation 83-1J... that's important), carefully examine both ends. On one end you'll see a small c-ring insert. Taking a narrow-bladed hacksaw, cut the end of the barrel connector along the axis of the barrel connector so that the blade bisects and cuts the middle of the c-ring insert. Voila! The insides now fall out! You'll find you have two plastic inserts and a center conductor. The barrel center conductor will fit over the end of the coax center conductor. Solder it to the coax center conductor so that the closest part of the barrel's center conductor from the aluminum jacket on the coax is 7/16" Insert one of the plastic inserts back into the barrel so that the end that was not cut will capture the insert. Take the end of the barrel that was cut by the hacksaw and screw it into the threaded end of the U50 coupler. Now take the U50 outer section and (after first putting Penetrox A around the outer portion of the aluminum jacket from the edge to about 3/4" back) slide the sleeve portion up and screw the outer portion into it. As it is being screwed together, two things happen: (1) The compression fitting clamps down on the aluminum sleeved coax. (2) The end of the barrel's center conductor will come right up snug with the end of the barrel. You are now an expert! You can go fit the other end with much greater ease! It works great. Be sure and waterproof it with Starbrite Liquid Electrical Tape or Scotch 33 or Scotch 88 plus some coax seal on top of that, plus another layer of Scotch 33 or Scotch 88 on top of that and you have yourself one Hell of a connection! The folks at N6IJ, have recently found a quick, simple termination to our 75 ohm surplus CATV coax (.75") used in longer runs at the site. Simply hacksaw the aluminum jacket, in quarters, about 1" along the axis of the coax, and use an Xacto knife and Needle Nose pliers to tear out the foam dielectric, about 3/4" deep into the clean cut end, and insert a Barrel UHF fitting, hose clamping the jacket tightly to the barrrel, and seal with tape. Use NoAlox sparingly between the barrel and the inside of the jacket. Do not use too much NoAlox, or else it may cause a short between the center and jacket. For another description and photos for making these CATV connectors, see May, 1992 QST under Hints & Kinks, or the ARRL UHF/Microwave Projects Manual. Here's another description for terminating hardline: For the 1/2 inch CATV try using a reducing compression union, 5/8" to 1/2" (True Value part 286-738). Cut the plastic coating (if it has it) back about 1.75". Cut the aluminum jacket about 1.5 inches from the end of the CATV. Use a plumber's tube cutter for clean edges. Then strip about 3/4" of the dielectric away from the center conductor. Put the 1/2" nut and the compression ring over the aluminum jacket. Shove the dielectric and center conductor into the compression union just as far as you can, making sure that the aluminum jacket gets inside the seat of the 1/2" end of the union. You should have an ample amount of the center conductor coming out the 5/8" end of the union. Slip the compression ring down on the seat of the union followed by the nut. Tighten it down. Take a UHF barrel and shove it on the center conductor. Make sure it also engages the seat of the compression union. The center conductor should go no more than halfway into the barrel. If you have extra on the center conductor, trim it to make it fit. Put the 5/8" compression ring on the UHF barrel followed by the nut. Crank it down making sure that things are tight and secure. When you put it up on the tower, take either some silicon tape or liquid rubber with you. Apply it generously over the entire connection followed with a good wrap of electrical tape. The center conductor of the 1/2" hardline may be a little bit smaller than the center of the UHF barrel. Go to the local hobby shop for some fuel line used in model airplanes, about the next to the smallest size they have. Solder a piece big enough to cover the center conductor in place and shove it into the barrel for a nice tight fit. For the 3/4 CATV, it's a different story. You will probably not find a 3/4 to 5/8 reducing compression union, they are apparently rare (if they exist at all). Try a 3/4" female hose thread connector that reduces to 1/2" female pipe thread, a 3/4" to 5/8" reducing male, and the compression nut for a 5/8" union. Cut away about 1.5" of the aluminum jacket. Using the 3/4 female, start it on the jacket and "score" threads into the jacket, just as far down as you can get it. Take the male and turn it into the end of the female that the CATV comes out of. Tighten it down. With as much of the dielectric as you can get into it, cut away the dielectric. Slide the UHF barrel over it, cut it where needed and secure it with the compression ring and nut. WX proof as above. All of the compression fittings and connectors are available from True Value hardware and about three bucks apiece. helps. * DO NOT use penetrox because with time it will migrate and cause a blow out (always in the middle of a European run in a contest) * DO use silicone grease between the aluminum shield and the barrel connector to keep corrosion down. * Seal it as well as you can * Do NOT use Radio Shack barrel connectors as they will invariably break down during the big JA runs in a contest Try to use hard splices as much as possible for the longest term solution. Use 1/8 inch hobby store brass tubing and slit it longitudinally with a dremel tool to slip over the center conductors that are butted together and soldered. Then lay the copper shield of RG-11 over the aluminum shield and smear it up with plenty of silicone grease and seal it well. WASPS Towers, for some reason, are a magnet for wasps that like to make their nests on them high above the ground. You will need a product like Wasp- Freeze, or Bee-Bopper to spray them from a distance if they build a nest on your tower or antennas. They are least active when it is dark and cold. Very early morning is a good time to attack them. If you get stung, the best sting remedies seem to be ammonia, and a paste made from Adolf's meat tenderizer and water, which contains an enzyme papain that will break down the poisons in the sting. BUILDING YOUR OWN BALUN Here's something by Ed Gilbert, WA2SRQ, on the effectiveness of homebrew choke baluns. They are cheap and effective. --------------------------------------------------------------------- Having access to a Hewlett-Packard 4193A vector impedance meter at work, I have made measurements on a number of baluns, coaxial and otherwise. For my beams I was particularly interested how many turns and on what diameter are optimum for air core coaxial baluns, and what the effect of bunching the turns was (formless). Using the remote programming capability of the HP4193A along with an instrument controller, I measured the magnitude and phase of each balun's winding impedance at 1 MHz intervals from 1 to 35 MHz. For comparison, I also made measurements on a commercial balun which consists of a number of ferrite beads slipped over a short length of coax. I've appended some of these measurements so you can draw your own conclusions. PVC pipe was used for coil forms. The 4-1/4 inch diameter baluns were wound on thin-walled PVC labeled "4 inch sewer pipe". This material makes an excellent balun form. It's very light weight and easy to work with, and I obtained a 10 foot length at the local Home Depot for about 3 dollars. The 6-5/8 inch diameter forms are 6 inch schedule 40 PVC pipe which is much thicker, heavier, and more expensive. Each test choke was close-wound on a form as a single-layer solenoid using RG-213 and taped to hold the turns in place. The lengths of cable were cut so there was about 2 inches excess at each end. This allowed just enough wire at the ends for connections to the HP4193A's probe tip. After data was collected for each single-layer configuration, the PVC form was removed, the turns were bunched together and taped formless, and another set of measurements was taken. I have only included the "bunched" measurements in the table for one of the baluns, but the trend was the same in each case. When compared to the single-layer version of the same diameter and number of turns, the bunched baluns show a large downward shift in parallel self-resonance frequency and poor choking reactance at the higher frequencies. Interpreting the Measurements ----------------------------- All the baluns start out looking inductive at low frequencies, as indicated by the positive phase angles. As the frequency is increased, a point is reached where the capacitance between the windings forms a parallel resonance with the coil's inductance. Above this frequency, the winding reactance is reduced by this capacitance. The interwinding capacitance increases with the number of turns and the diameter of the turns, so "more is not always better". The effects of a large increase in interwinding capacitance is evident in the measurements on the balun with the bunched turns. This is probably a result of the first and last turns of the coil being much closer together than the single-layer coil. An important requirement of these baluns is that the magnitude of the winding reactance be much greater than the load impedance. In the case of a 50 ohm balanced antenna, the balun's winding impedance is effectively shunted across one half the 50 ohm load impedance, or 25 ohms. A reasonable critera for the balun's winding impedance for negligible common mode current in the shield is that it be at least 20 times this, or 500 ohms. The measurements show, for example, that 6 turns 4-1/4 inches in diameter meet this criteria from 14 to 35 MHz. The measurement data also reveals the power loss these baluns will exhibit. Each of the measurement points can be transformed from the polar format of the table to a parallel equivalent real and reactive shunt impedance. The power dissipated in the balun is then the square of the voltage across it divided by the real parallel equivalent shunt impedance. While this calculation can be made for each measurement point, an approximate number can be taken directly from the tables at the parallel resonance points. At 0 degrees phase angle the magnitude numbers are pure resistive. I didn't record the exact resonance points, but it can be seen from the tables that the four single-layer baluns are all above 15K ohms, while the ferrite bead balun read about 1.4K. These baluns see half the load voltage, so at 1500 watts to a 50 ohm load, the power dissipated in the coaxial baluns will be less than 1.3 watts, and the ferrite bead balun will dissipate about 13.4 watts (neglecting possible core saturation and other non-linear effects). These losses are certainly negligible. At 200 ohms load impedance, the losses are under 5 watts for the coaxial baluns and 53.6 watts for the ferrite beads. Conclusions ----------- - A 1:1 coaxial balun with excellent choking reactance for 10 through 20 meters can be made by winding 6 turns of RG-213 on inexpensive 4 inch PVC sewer pipe. - For 40 or 30 meters, use 12 turns of RG-213 on 4 inch PVC sewer pipe. - Don't bunch the turns together. Wind them as a single layer on a form. Bunching the turns kills the choking effect at higher frequencies. - Don't use too many turns. For example, the HyGain manuals for my 10 and 15 meter yagis both recommend 12 turns 6 inches in diameter. At the very least this is about 3 times as much coax as is needed, and these dimensions actually give less than the desired choking impedance on 10 and 15 meters. Measurements ------------ Magnitude in ohms, phase angle in degrees, as a function of frequency in Hz, for various baluns. 6 Turns 12 Turns 4 Turns 8 Turns 8 Turns Ferrite 4-1/4 in 4-1/4 in 6-5/8 in 6-5/8 in 6-5/8 in beads sngl layer sngl layer sngl layer sngl layer bunched (Aztec) ---------- ---------- ---------- ---------- ---------- ---------- Frequency Mag Phase Mag Phase Mag Phase Mag Phase Mag Phase Mag Phase 1.00E+06 26 88.1 65 89.2 26 88.3 74 89.2 94 89.3 416 78.1 2.00E+06 51 88.7 131 89.3 52 88.8 150 89.3 202 89.2 795 56.1 3.00E+06 77 88.9 200 89.4 79 89.1 232 89.3 355 88.9 1046 39.8 4.00E+06 103 89.1 273 89.5 106 89.3 324 89.4 620 88.3 1217 26.6 5.00E+06 131 89.1 356 89.4 136 89.2 436 89.3 1300 86.2 1334 14.7 6.00E+06 160 89.3 451 89.5 167 89.3 576 89.1 8530 59.9 1387 3.6 7.00E+06 190 89.4 561 89.5 201 89.4 759 89.1 2120 -81.9 1404 -5.9 8.00E+06 222 89.4 696 89.6 239 89.4 1033 88.8 1019 -85.7 1369 -15.4 9.00E+06 258 89.4 869 89.5 283 89.4 1514 87.3 681 -86.5 1295 -23.7 1.00E+07 298 89.3 1103 89.3 333 89.2 2300 83.1 518 -86.9 1210 -29.8 1.10E+07 340 89.3 1440 89.1 393 89.2 4700 73.1 418 -87.1 1123 -35.2 1.20E+07 390 89.3 1983 88.7 467 88.9 15840 -5.2 350 -87.2 1043 -39.9 1.30E+07 447 89.2 3010 87.7 556 88.3 4470 -62.6 300 -86.9 954 -42.7 1.40E+07 514 89.3 5850 85.6 675 88.3 2830 -71.6 262 -86.9 901 -45.2 1.50E+07 594 88.9 42000 44.0 834 87.5 1910 -79.9 231 -87.0 847 -48.1 1.60E+07 694 88.8 7210 -81.5 1098 86.9 1375 -84.1 203 -87.2 778 -51.8 1.70E+07 830 88.1 3250 -82.0 1651 81.8 991 -82.4 180 -86.9 684 -54.4 1.80E+07 955 86.0 2720 -76.1 1796 70.3 986 -67.2 164 -84.9 623 -45.9 1.90E+07 1203 85.4 1860 -80.1 3260 44.6 742 -71.0 145 -85.1 568 -51.2 2.00E+07 1419 85.2 1738 -83.8 3710 59.0 1123 -67.7 138 -84.5 654 -34.0 2.10E+07 1955 85.7 1368 -87.2 12940 -31.3 859 -84.3 122 -86.1 696 -49.9 2.20E+07 3010 83.9 1133 -87.8 3620 -77.5 708 -86.1 107 -85.9 631 -54.8 2.30E+07 6380 76.8 955 -88.0 2050 -83.0 613 -86.9 94 -85.5 584 -57.4 2.40E+07 15980 -29.6 807 -86.3 1440 -84.6 535 -86.3 82 -85.0 536 -58.8 2.50E+07 5230 -56.7 754 -82.2 1099 -84.1 466 -84.1 70 -84.3 485 -59.2 2.60E+07 3210 -78.9 682 -86.4 967 -83.4 467 -81.6 60 -82.7 481 -56.2 2.70E+07 2000 -84.4 578 -87.3 809 -86.5 419 -85.5 49 -81.7 463 -60.5 2.80E+07 1426 -85.6 483 -86.5 685 -87.1 364 -86.2 38 -79.6 425 -62.5 2.90E+07 1074 -85.1 383 -84.1 590 -87.3 308 -85.6 28 -75.2 387 -63.8 3.00E+07 840 -83.2 287 -75.0 508 -87.0 244 -82.1 18 -66.3 346 -64.4 3.10E+07 661 -81.7 188 -52.3 442 -85.7 174 -69.9 9 -34.3 305 -64.3 3.20E+07 484 -78.2 258 20.4 385 -83.6 155 -18.0 11 37.2 263 -63.2 3.30E+07 335 -41.4 1162 -13.5 326 -78.2 569 -0.3 21 63.6 212 -58.0 3.40E+07 607 -32.2 839 -45.9 316 -63.4 716 -57.6 32 71.4 183 -40.5 3.50E+07 705 -58.2 564 -56.3 379 -69.5 513 -72.5 46 76.0 235 -29.6 Ed Gilbert, WA2SRQ eyg@hpnjlc.njd.hp.com ATTACHING ELECTRICAL ENCLOSURES TO YOUR TOWER Use some galvanized, punched strut. It's a channel shaped material, also referred to as Kindorf, Power Strut, Uni Strut, as well as many other names. Bolt this to the tower using U-bolts, or clamps, then use strut nuts, or spring nuts inside the channel to screw the box to.