| Hi Tom,
based on my experience with Nav antennas and carbon, I would say your chances of getting a com antenna to work inside carbon are about nil, even with NO paint over the top.
In fact, I have yet to hear (although I hope it's possible ) that someone got really good (e.g. 100 mile line of sight) range out of a Bob Archer com antenna in a glass vstab.
What seems to work is a whip (monopole) on the belly with either a sheet metal ground plane or a star of copper tape. The RADIUS of the ground plane should ideally be 22" although people have done well in the high teens. ...so placement is an issue. You can build your own whip out of fiberglas and copper tape and make it more aerodynamic if you wish. Length is critical and seems to come out to 20.8" with 1/2" copper tape (as predicted by Jim Weir). You want to get the ferrite donuts from Jim Weir if you go that route.
Colyn On Feb 23, 2011, at 9:09 AM, TOM GARDINER wrote: Folks I am experiencing a dreadful time getting my COM radios to perform to their full (or even half) potential in my LNC2. I have two Bob Archer's mounted in the tailcone and in the proper orientation with a VSWR of around 1.5 with RG 400 cable. The antennas are fed by two Garmin 430s with a measured output of 8 watts each. The thing is that ATC and my flying friends report a consistently weak signal and the same applies on reception on my end. My airplane has the carbon tail and I built the seat bench using carbon on foam (bad idea in hindsight). I have tried another type of antenna that is a dipole with a balun mounted in the center of the baggage section in a vertical orientation but with little or no improvement in results. I am beginning to suspect the Lancair supplied Gray epoxy primer which I understand contains aluminum oxide in the base I am now considering mounting an external antenna but thought I would ask if anybody had experienced similar issues and subsequently corrected them. Any help/advice would be very much appreciated Thanks Tom LNC2 24 hrs
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