Homebrew projects for radio & electronics enthusiasts
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There is a huge amount of relevant information you should know before building a tower.
Here's a collection of information that I have gathered that will give you a boost. You'll be glad you took the time:
N1LO's GUYED TOWER TOPIC SUMMARY
Here is some great information from Kurt K7NV ( now an SK). We met on the TowerTalk forum many years ago and enjoyed a mutual professional respect. I gave him permission to host my tower guide document, which he had edited by a friend and posted it on his own website. Unfortunately after his passing, Kurt's website went offline but it can still be found on the internet way back machine site as an archived, saved website. Here is Kurt's archived notebook page:
The K7NV Notebook
Kurt posted some engineering deflection analyses to show how towers react to windloads and why it is so important to select guy materials and sizes for low stretch as well as adequate ultimate breaking strength:
Guyed Tower Safety Analyses by Kurt, K7NV
I used the information I collected above to help me build my own tower, starting in 1998. I had a 110' tower, made from 11 sections of Rohn 25. I oversized the guy cables and chose all the components carefully to withstand weather and occasional downed limbs from nearby trees. I started learning to climb by helping a couple of other experienced tower climbers in my area. It is truly an adventure of the body and mind to climb a tower, learn to trust your safety gear, perform competent work at height, and get back down safely.
I crowned my tower with a Force 12 C3E trapless HF tribander at 112 ft (2 ft above the top plate) that could operate 20-10m. Above that, a Cushcraft 13B2 2m beam at 115 ft, and on the top of the 2 x 1/4 in aluminum mast, I installed an 8 ft copper-clad ground rod, pointed upwards. The ground rod acted as an air terminal to protect the tower and antennas below it from lightning. I had a 17 ft VHF/UHF vertical and a discone scanner antenna side mounted on the tower, along with two fiberglass side arms and pulleys, used to support wire antennas. I used an old-school tower builder's trick and unfurled the free ends of each guy cable into static dissipators, with multiple sharp points. Yes, it did work to reduce lightning strikes! Here's one of the few good pictures I have of my tower, taken in 2004.
My tower stood up to hurricane Isabel that came through Southeastern Virginia in September 2003. I stepped outside during one of the wind gusts to snap a quick picture. I anticipated the direction of the strongest winds before the hurricane came through and had the beam pointed into the wind as best I could. You can see all of the beam elements flexing, all of the other components on the tower blowing around, even the side mounted VHF/UHF vertical was flexing. You can see shredded leaves, flying through the air, captured in this moment.
I enjoyed that tower for 10 years until Mother Nature took it away from me. Yes, even though I had over engineered the guy cables and did everything I could to make it strong, it was not strong enough to withstand the load from an entire tree that fell over square across one of the guy cables. It was a 2 ft diameter maple tree that had a hidden rotten base and broke right off during a minor storm. Interestingly, the guy cable did not break, but my heart did! The compressive load of the weight of the tree caused one of the tower legs to buckle, and the entire tower folded up in a Z shape within a small radius. At the time, I just happened to be in my car parked in the driveway about 40 ft away, installing a radio. I heard some wood crackling and thought that a small branch was falling down. I looked up just in time to see the tower crumple. I shall never forget that in all my days. The oversized guy cables and sturdy screw anchors held fast, containing the tower within a small radius. It did not hit me, it did not hit my house, and even the antennas were undamaged, because one of the guy cables tangled in the giant hickory tree next to the tower, preventing it from slamming completely to the ground. This was a time of great difficulty and stress in my life from this and other pressures at work. It took quite some time for me to get around to cleaning up the mess and salvaging many components and antennas.
Here are some photos from my original tower installation. This was before I had discovered digital photography. These are photos of old color prints that do not have much detail, but are interesting and educational nonetheless. What an adventure!
N1LO'S TOWER PICTURE GALLERY
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Have you found something useful here? Got a comment? Drop me a line: n1lo (remove 'nospam' from address when sending)
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