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Look at it closely. It is three wires (Radio Shack rotor wire) joined at
opposite ends to make one long wire. The 70 foot model actually has a "run" of 210 feet - 105 feet on each side. Funny, Radio Shack rotor wire comes in 70 foot rolls. Attach ladder line to a middle insulator. Add up the cost and you'll save a lot by doing it yourself. I have seen a Cobra and it looks very well made but I have never used one. The principal is called linear loading, and it is a very effective way of getting maximum benefit out of short antennas. It is far more efficient than coils. ON4UN's book talks a lot about it but I couldn't find much discussion on the effect of having the wires so close together. He does advise, on page 8-13 of the Third Edition, "make sure the separation between the element and the folded linear-loading device is large enough, and that you use high-quality insulators to prevent arc-over and insulator damage." He doesn't define "enough" and the phrasing of the sentence makes it sound like the only concern with having them too close is arc-over. On the same page, he warns modeling is "very tricky." From the discussion that follows on this thread, I would say that is an understatement. -- Radio K4ia Craig "Buck" Fredericksburg, VA USA FISTS 6702 cc 788 Diamond 64 "Bert Craig" wrote in message . net... Opinions please. :-) http://www.k1jek.com/ It got pretty rave reviews on eHam. http://www.eham.net/reviews/detail/3...9a7885c56da2cc -- Vy 73 de Bert WA2SI FISTS #9384 QRP ARCI #11782 |
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