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On Sun, 24 Jul 2011 15:52:08 -0700 (PDT), Gary
wrote: Other than the obvious (he was mistaken in what he reported to me) any ideas as to what went wrong? You forgot to offer burnt offerings to the radio propagation gods. I don't think he will ask for any more advice from me. 80 meters at 100 miles is in the range of the NVIS propagation. 25 miles is about the limit for 80m ground wave, and 300 miles is about where sky wave starts. The problem with NVIS is that it's really picky about the height of the antenna above the ground. I don't have very much NVIS experience to offer any guaranteed suggestions on how to make NVIS work reliably. I assume the kid will be talking to his father regularly. My limited and unscientific tinkering empirically determined that the NVIS horizontal antenna wire has to be fairly close to the ground. A dipole that close to the ground has a fairly low impedance. See "height above ground" section: http://www.w0ipl.net/ECom/NVIS/nvis.htm My guess(tm) is that with the antenna near the ground, most of the RF goes straight up, which is what you want for NVIS, while an elevated antenna delivers more RF towards the horizon. There are plenty of web sites expounding on NVIS antenna and propagation worth reading. Tell the kid what you think happened, but let him do the research and tinkering. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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