Message-ID: <006e01bf5101$3e6225e0$42064498@us.oracle.com>
From: "Steven B. Janicki" <sjanicki@us.oracle.com>
To: <lancair.list@olsusa.com>
Subject: Why I Plan To Use A Diplexer Vs. Installing a Second Com Antenna
Date: Mon, 27 Dec 1999 23:00:35 -0800
Mime-Version: 1.0

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http://www.pavionics.com/antcomcompsite.htm

I have referenced the above url which takes you to
ANTENNA TIP # I COM ANTENNAS FOR COMPOSITE AIRCRAFT
by Bob Archer of Sportcraft Antennas


I chose to go with a Diplexer because of the above article. I will add the
key sentence and you may visit the above URL to read the entire article.
Again my descision and I am not trying to influence others just sharing my
logic.

PAGE 2

When installing any antenna remember that antennas do interfere with each
other when installed too close together and that close metallic (or
conductive: remember graphite) objects that are as long or longer in the
same polarization/plane will reflect RF energy away from them. Close meaning
one wave length or closer and closer being worse. One wave length is about
eight feet at VHF frequencies. Less than a quarter wave length is really bad
from both a VSWR and the radiation pattern stand point. The formula for
wavelength is: 11803/ FREQ. in MHz. = wavelength in inches. So there being
only one good location for an internal COMbI antenna (unless you have twin
verticals) and antennas don't work well close together, it follows that for
aircraft with dual transceivers and no good location for a second antenna
there is a need for a two set switching device of some type.

Regards,

Steven
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