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Subject: Re: [LML] Legacy Com Antenna
From: Colyn Case <colyncase@earthlink.net>
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Dean,

I just went through this with my IVP.
Considerations:
- a big round ground plane (radius on order the total length of the =
antenna) is nearly mandatory to really have it work.
if you can find two such areas on your belly that would be the optimal =
solution.
- diplexors involve substantial signal loss.  =20
- a switch is another possibility but that also is a reliability issue.

Given all that, I think my preferred solution is to totally optimize my =
number comm: no diplexors, no connectors, really good ground plane; and =
then do the best I could with a second antenna and use that for comm 2.  =
 ...and provide myself a connector between the comm 2 antenna and comm 2 =
where I could manually plug in my portable instead of comm 2.

caveat:   I'm a total amateur and I'm sure this post will attract an =
expert opinion.

Colyn


On Dec 30, 2011, at 12:07 PM, Dean Whiting wrote:

I was looking for some advice about communication antennas.  The legacy =
is setup to have one com antenna.  We want a capable IFR airplane and I =
am hesitant to have one antenna with a diplexer (or is it duplexer, I've =
seen it both ways) as a possible single point of failure.  Is this the =
method that most people are using?  If you mounted a 2nd com antenna, =
where did you place it?  I searched the archives and found someone else =
who asked the same question but I couldn't find the answer.  Any other =
input or advice on the subject would be appreciated.

Dean Whiting

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