Dean:
I used Bob Archer antennas on my IV P with excellent results. The vertical tail unit is COM 1. I placed the wingtip version in each tip. The right tip (also containing the magnetic heading sensor) feeds the G900 nav/gs 4 way splitter recommended by Garmin while the left tip is the COM 2 antenna. Tuning a distant ATIS shows both com antennas have the same sensitivity. You may hear that com antennas should be vertically polarized which is correct in theory. In actual practice the scatter experienced by both the XMIT and received signals makes the polarization effect negligible.
I also placed the GPS/XM antennas below the eglass turtledeck. The xpdr antenna is the only external antenna which is on the bottom using the carbon fiber as a ground plane with excellent results.
Jack Morgan
On Jan 3, 2012, at 6:00 AM, Lancair Mailing List 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