| Hi Tom,
I put the same Archer nav antenna in the other wing tip and used it for com 2. The slightly higher frequencies of the com range are only a few DB lower as the antenna is sufficiently broad band. As a practical matter the vertical polarization deemed best for com has little effect due to scatter which the com signals experience. I can tune an ATIS at the fringe distance and compare the 1 and 2 audio quality with only a slight difference. If you locate the compass magnetometer in the wing tip, put it on the nav side as the com transmit power could upset it's magnetic sensor. The wing tips must be eglass rather than the carbon fiber winglets common on the earlier IV's.
I used the archer MBR antenna on the inside of the wing fairing and got by. It seems too close to the fuselage but seems to work OK.
I placed the two GPS/XM antennas under the eglass turtle deck. After paint completion, I compared the signal strength on my G900 with the antennas outside the airplane and mounted under the eglass and found no difference in signal strength. I have had no reception issues with GPS. My paint choice was base coat/clear coat non metallic white in the antenna area. I suspect a metallic paint in the antenna area could impair reception but have no data to support that guess.
The XPDR antenna is on the bottom and is the only external antenna. The fiber provides sufficient ground plane in my opinion. Moving it aft as necessary to clear your belly tank is not an issue and the fairing location should be OK also with a foil ground plane extending well into the fuselage fiber area. I would try to center it on the fuselage however.
Hope this helps.
Jack Morgan IVP On Mar 3, 2013, at 6:00 AM, Lancair Mailing List wrote: Subject: Looking for advise on Antenna locations for IVP
Date: March 2, 2013 2:51:44 PM EST
I did a search on the LML archives and found a pot pouri of questions, problems and tips, but much of the info had to do with glass planes (not carbon fiber), and I have some unique challenges as well. I have already installed the Bob Archer com antenna in the vert/stab and a nav antenna in the winglet (think just one). My unique challenge is the fact that most of my belly between the gear and forward to the firewall is fuel tank, so this area is unusable for antennas. I think, based on complaints, that I want at least one more com antenna. As shown in the attached picture, of the aft fuselage area with my A/C, there is no way I can get a large ground plane in there. With carbon, do they usually install it in the fuselage (wondering if the ground plane does any good behind the carbon)? I may be able to get a "segmented" one in there, with part of the ground plane inside the A/C condenser box, and run a ground strap or strip between the segments at each end of the "pie slice" cut out for the A/C. Otherwise I am limited to a smaller ground plane, or installing one on the outside of the skin (already body worked and in primer). Also, for the transponder and Marker beacon antennas, wondering if I could place one at the rear of each wing fairing, as I think the ground plane (G/P) on those would be smaller, and the G/P could be "seen" easily through the fiberglass of those fairings. My understanding is the gound plane need only be as large in radius as the length of the actual antenna it is connected to? Thanks in advance for any advice. Tom Sullivan
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