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On Sun, 01 Feb 2004 01:19:22 GMT, Orval Fairbairn
wrote: BTW, it DOES make a difference if you hook up the comm antenna to the nav and vise-versa. One is horizontilly polarized while the other is vertically polarized. Both receiver sensitivity and xmit capability cna be severely compromised. Yes, but: The Narco "Comm" antenna is the transmitter, and the "Nav" antenna provides the signal for the receivers for BOTH the Nav and the Comm channels. The Comm receiver is *supposed* to use horizontally-polarized antenna. I know, it ain't right optimum. But that's the way Narco wants it. The original two antennas in the airplanes were coax dipoles with baluns. Both horizontally oriented, both located UNDER the aluminum-covered turtledeck. They were truly duplicates. And they worked quite well, for almost 20 years. One crapped out a few years back, and that's when I built the surface-mount antenna described in my "Antenna Madness" posting about three years ago. So I've got one horizontal, and one vertical. I try to hook the old dipole (the horizontal one) to the receiver and the new vertical one to the transmitter. I actually run the coaxes in two pieces, with the connector right by the seat, so I can switch antennas easily if I detect a problem. This is handy for troubleshooting...a couple of times, I've noticed that I wasn't receiving signals very strong, or folks complained that they couldn't hear me very well. I've been able to quickly swap antennas and compare. Ron Wanttaja |
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