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|  |  | Dean, 
 It is possible to use a single comm antenna but it takes something like this:
 
 http://www.aircraftspruce.com/catalog/avpages/comantswtich601.php
 
 It's not a very common installation and it's a lot more expensive than a second antenna!
 
 My layman's understanding is that transmissions from one radio become over-powered receptions to the other radio.  So most commonly, two comms each use a dedicated antenna.
 
 On a Legacy, the second antenna can go aft of the primary.  It needs to be centered a minimum of two antenna lengths from the other comm antenna.  That makes it a challenge to use a straight antenna as it may hit the ground before the tail tie-down.  We've put an antenna in that area, and we may have ended up using a bent whip like a Comant CI-122.
 
 Nav antennas can be split without worry.
 
 Dave Saylor
 AirCrafters
 140 Aviation Way
 Watsonville, CA 95076
 831-722-9141 Shop
 831-750-0284 Cell
 
 
 
 On Fri, Dec 30, 2011 at 9:07 AM, Dean Whiting <dean.whiting@gmail.com>  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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