Posted: 5/3/2012 6:51:27 PM EDT
Looks like the latest round of thunderstorms that rolled through Indy earlier in the week took out part of the 40-6m OCFD antenna in the trees behind our home. If you remember, this isn't the first time this antenna has been damaged by high winds. This time it's the east end that pulled loose from the insulator and is hanging down about ten feet above the ground. Still works well enough for WSPR to send a 5w signal heard by a couple of stations in Israel on 30m. 
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STILL WORKS 
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Sorry to hear about your bad luck.
Nice pictures though. Maybe the Palm trees are too flexible for the Indiana weather and stretch things until they break? Try a hardwood tree for support if you have any.
Sorry, I'm just in one of those moods tonight... ETA: You might try a suspended weight on the end under the pulley. It will move easily but hold the antenna taught. |
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You might try a suspended weight on the end under the pulley. It will move easily but hold the antenna taught. I have a couple of springs inline to try to relieve some of the stress when the trees move, but that doesn't seem to be enough. ALKVA suggested the hanging weights the last time this happened also. May have to give it a try. 
The previous failure was where the wire wrapped back on itself after going through the insulator. Looks like the same type of failure this time, but on the other end. 
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I use the exact same wire with a lot less shock absorption (no pulleys, no springs) and have never had it break, not in any ice or wind storm. Max. winds survived so far were gusting to 70. However I tie a figure-eight-on-a-bight knot in the end, I don't wrap it like you do (and I don't bother with fancy heat shrink).
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Perhaps a wire tie or clamp would be in order. I'm open to anything now that I've had two failures in a year. Quoted:
The wire itself is holding up well. It's stranded 14awg THHN from Lowes.
How is the jacketed stuff working for you? I've hard ups and downs. Next time my copperweld breaks, i'm tempted to get some standard 12 ga THHN to replace it. |
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I use the exact same wire with a lot less shock absorption (no pulleys, no springs) and have never had it break, not in any ice or wind storm. Max. winds survived so far were gusting to 70. However I tie a figure-eight-on-a-bight knot in the end, I don't wrap it like you do (and I don't bother with fancy heat shrink). http://pages.swcp.com/~nmmc/climbrocks/knots/figure8.GIF I may try that knot and skip the spring. aa777888-2. The pulleys are convenient to raise and lower (for repairs like this) one side or the other. ETA: Just to clarify, you tie that knot with the antenna wire to attach it to the insulator? I use a similar knot, a Bowline, on the rope side of the insulator that has never failed. Use it to support the pulleys also. BOWLINE 
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I know you have thought of this, but a weighted line will elimate the wind related stress.
Leave the pulleys, as you have them and replace the springs with a heavy lead weight. Sufficiently heavy to tighten the line as you want. As the trees move back and forth, the lead weight will move up and down but the tension on your antenna will not change.... |
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I know you have thought of this, but a weighted line will elimate the wind related stress. Leave the pulleys, as you have them and replace the springs with a heavy lead weight. Sufficiently heavy to tighten the line as you want. As the trees move back and forth, the lead weight will move up and down but the tension on your antenna will not change.... +1 
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For the failure at the insulator I use about 3 times the number of turns of wire and then use lots of cheap electrical tape. I also run tuned feeders so, other than balance, the lengths of the antenna are not critical. The tape will be better (Stronger) than the shrink wrap. I'd suspect that UV exposure is weakening the shrink tubing. For springs, in the past I have used screen door springs but the pulleys and counter weights are probably better. My old H.S. teacher used to talk about 1/2 window weights. R.I.P. Mr A. 73, Rob |
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I use the exact same wire with a lot less shock absorption (no pulleys, no springs) and have never had it break, not in any ice or wind storm. Max. winds survived so far were gusting to 70. However I tie a figure-eight-on-a-bight knot in the end, I don't wrap it like you do (and I don't bother with fancy heat shrink). http://pages.swcp.com/~nmmc/climbrocks/knots/figure8.GIF I may try that knot and skip the spring. aa777888-2. The pulleys are convenient to raise and lower (for repairs like this) one side or the other. ETA: Just to clarify, you tie that knot with the antenna wire to attach it to the insulator? I use a similar knot, a Bowline, on the rope side of the insulator that has never failed. Use it to support the pulleys also. BOWLINE http://reidsmarine.com/images/knots/bwln.jpg Yes, I tie that knot into the antenna wire. It is easier to put into the wire than a bowline, which I also use for my support lines, same as you. I don't bother with insulators, the 550 cord I use as supports is good enough. I tie the figure eight into the wire, then tie the 550 cord into the wire loop with a bowline. I have two antennas set up similarly. The one that is most similar to yours is a dipole that uses the peak of my roof as a center support point. Each leg is about 150' long of the same wire you are using. Each wire is stood off the house with about 1' of 550 cord and supported by a long piece of 550 over a tree limb at the far ends. These are tied off to tree bases, in this case with no pulleys and with the knots as discussed above at each end of each wire. I leave a foot or two of sag in each wire. The other antenna is a fancier installation of my 140' long Cobra Ultralite Senior. This antenna has pulleys at both ends and they are indeed very convenient for maintenance. At one end I even set up a 2:1 pulley system to ease tensioning. However both ends are tied off to hard points (tree bases) and the only shock absorption in the system is the stretch in the 550 and I leave a couple of feet of sag in the wire. The Cobra has withstood everything that nature could throw at it for 3 or 4 years now except for a large tree that fell square across it––hardly a fair test! The large dipole has survived one winter so far. |
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How is the jacketed stuff working for you? I've hard ups and downs. Next time my copperweld breaks, i'm tempted to get some standard 12 ga THHN to replace it. Try MTW (Machine Tool Wire) for the long haul. MTW is more flexible, and the black I have has held up to UV well for the 5 or 6 years I've had it. http://www.wireandsupply.com/product_p/mtw-14g.htm http://www.wireandsupply.com/product_p/mtw-12g.htm MTW is only a few cents more per foot than THHN. |
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Perhaps it is good that the wire is pulling apart at the insulator, rather than actually breaking the wire. Like blowing a fuse instead of toasting the whole radio. Great analogy, I was thinking the same thing.  Any discontinuity, like a knot or a turn around an attachment point, will be weaker than the rest of the rope/line/wire. |