Antenna separation

lr172 · #1 04-08-2018, 02:06 PM

I am planning antenna placement for the 10. The Comms are under the rear seats with almost 4' of separation. I would like to mount the transponder antenna and UAT antenna under the front seats. I will have a bit over 2' of separation between them and over 3' from the Comms.

Will this separation be adequate? I read the the transponder antennae should be 2' apart, but also read 6' apart.

I appreciate any guidance here.

Larry

BobTurner · #2 04-08-2018, 03:28 PM

Coms: I?d like to see a bit more separation - but lots of 172s have antennas on the cabin roof, about 4 feet apart. Can?t argue with success! Don?t expect to be able to have the copilot use one radio while the pilot uses the other. Also, I do find that once in a while, my belly whip can?t communicate with ground. Usually a small turn fixes the issue, or I switch to the wingtip antenna.
UAT: I?d be a bit concerned about my UAT receiver (especially if it?s dual band) being overloaded and unuseable when the transponder transmits. Some brands have ?inhibit? lines to keep this to a mimimum. Otherwise I?d try to find a more distant location for one of them (maybe remote mount the UAT in the tail).

Carl Froehlich · #3 04-08-2018, 05:49 PM

If you use a remoter ADS-B receiver (like is used in the SkyView system) you can mount the receiver and antenna aft near the battery. This moves the ADS-B antenna a good distance from the transponder antenna.

I mounted the transponder antenna under the co-pilot seat. Both comm antennas are mounted in the tunnel area, one on each side, one forward just behind the wing spar and one aft. The antenna are mounted toward the sides of the tunnel to keep distance to the elevator push tube. This makes access to the antennas easy.

Carl

N941WR · #4 04-08-2018, 06:52 PM

(This on a -9, so your mileage may vary.)

I put my transponder antenna just aft of the firewall, on the right side and then added the ADS-B antenna in the same place on the left side.

No issues with it being blanked, even though both antennas is right next to the left and right gear legs.

(My Comm antenna is bolted through the spar flange, forward of the spar. This kept me from having to run more wires through the spar, which has limited space. If/when I add a second comm antenna, it will go on the right side.)

Northernliving · #5 04-08-2018, 06:54 PM

The Dynon install manual says that ADS-B and transponder should be 2ft or more in separation. Page 347 or Section 14-9 of this manual. http://dynonavionics.com/public_html...v_AD_v15_3.pdf

lr172 · #6 04-08-2018, 08:21 PM

Quote:

Originally Posted by BobTurner

Coms: I’d like to see a bit more separation - but lots of 172s have antennas on the cabin roof, about 4 feet apart. Can’t argue with success! Don’t expect to be able to have the copilot use one radio while the pilot uses the other. Also, I do find that once in a while, my belly whip can’t communicate with ground. Usually a small turn fixes the issue, or I switch to the wingtip antenna.
UAT: I’d be a bit concerned about my UAT receiver (especially if it’s dual band) being overloaded and unuseable when the transponder transmits. Some brands have “inhibit” lines to keep this to a mimimum. Otherwise I’d try to find a more distant location for one of them (maybe remote mount the UAT in the tail).

The UAT will be a Uavionix and it is trying to do dual band on a UAT antenna, so already operating around the fringes. Maybe I'll install it behind the baggage bulkhead with the antenna back there as well to avoid any compromises on reception.

Thanks to all for the input and ideas.

Larry

GalinHdz · #7 04-09-2018, 06:39 AM

Quote:

Originally Posted by lr172

I am planning antenna placement for the 10. The Comms are under the rear seats with almost 4' of separation. I would like to mount the transponder antenna and UAT antenna under the front seats. I will have a bit over 2' of separation between them and over 3' from the Comms.

Will this separation be adequate? I read the the transponder antennae should be 2' apart, but also read 6' apart.

I appreciate any guidance here.

Larry

IMHO this should be fine.

Don't overthink this. Follow the Mfg recommendations since they know their equipment better than anybody on this board.

RandyAB · #8 04-09-2018, 08:53 AM

With the Garmin stuff, (I don't know about other manufacturers), there are blade antennas that will handle both the ADSB in and out in one antenna. I put the VHF bent whips under the passenger seats and will put the blade for the transponder under the passenger seat. I know of others that have this setup and are happy with it.

airguy · #9 04-09-2018, 09:47 AM

I have my two comm antennae (bent whip) on the far left and right sides of the airplane under the seat pans, transponder is in mid-tail area about a foot forward of the static port location and my ADSB UAT receive antenna is mounted under the seat pans centered right between the two comm antennae. This has worked perfectly for me from an RF perspective, the only issue I had with it was self-induced with cheap coax and easily resolved.

ebyars · #10 04-09-2018, 06:23 PM

Quote:

Originally Posted by lr172

The UAT will be a Uavionix and it is trying to do dual band on a UAT antenna, so already operating around the fringes. Maybe I'll install it behind the baggage bulkhead with the antenna back there as well to avoid any compromises on reception.

Thanks to all for the input and ideas.

Larry

That's exactly where I installed mine and it's working great.