RV-10 Comm Antenna Placement

[HighFlying]

So first I will apologize for writing yet another thread about the placement of antennas on an RV-10. There are hundreds of posts on the topic and I have read most of them. I appreciate top and bottom is best for diversity, not so much for aesthetics. My current thinking/plan is to put one Comant Ci-122 under the left rear passenger seat with coax going to tailcone for remote radio location and another Comant Ci-122 under the copilot seat, coax going to the panel. This gets about 4' of distance and gets them out of each other's radiating pattern. Will that be enough separation for simultaneous transmitting on the comms? I am also planning on SDS EFI so things are getting a little crowded under that seat with return fuel lines and such but I think it will work. Also, I am thinking the transponder will go behind the firewall in the tunnel. Is there a downside to this approach that I am not accounting for? Exhaust streams, potential performance issues, something else???

 

[Avanza]

So first I will apologize for writing yet another thread about the placement of antennas on an RV-10. There are hundreds of posts on the topic and I have read most of them. I appreciate top and bottom is best for diversity, not so much for aesthetics. My current thinking/plan is to put one Comant Ci-122 under the left rear passenger seat with coax going to tailcone for remote radio location and another Comant Ci-122 under the copilot seat, coax going to the panel. This gets about 4' of distance and gets them out of each other's radiating pattern. Will that be enough separation for simultaneous transmitting on the comms? I am also planning on SDS EFI so things are getting a little crowded under that seat with return fuel lines and such but I think it will work. Also, I am thinking the transponder will go behind the firewall in the tunnel. Is there a downside to this approach that I am not accounting for? Exhaust streams, potential performance issues, something else???

You may find that when on ground it may
be difficult to contact TWR on some airports. Transmission is dependent on line of sight. I would suggest atleast one antenna on top.

Good luck

 

[Carl Froehlich]

Keep in mind mounting any antenna under the rear seats will require modifications to allow future access. Not impossible but options other than under the rear seats are available.

What I did (and will repeat on the new RV-10 build):
- Both comm antennas are mounted under the tunnel, one forward and one aft. This provides easy future access.
- One antenna is biased to the left side of the tunnel, the other to the right. This eliminates potential interference between coax runs and the elevator push tubes.
- The antenna backing plates are joggled to allow for one side to share the fuselage skin to rib line a rivets. The antenna mount screws are just inboard of this rib.
- XPDR antenna is mounted under the co-pilot seat.
- ADS-b antenna (and SkyView receiver) are mounted just aft of the baggage compartment bulkhead.

This does support the ability to have the pilot transmit on one radio and the copilot to transmit on the other (Spilt Mode). I caution however that this capability is very dependent on your radio selections. For example I understand the Garmin GTR-200 (series) install instructions provides guidance to add the “receiver desense” connection between the radios as a mitigation of receiver front end overload when transmitting on the other radio. I will defer to the Garmin experts but I assume following this guidance translates to no split mode radio communications.

I run the GTN-650 and Dynon radio as Comm #2. This antenna placement has worked well for me.

The XPDR antenna mounted behind the firewall close to the exhaust stream would not be my choice. If you are using a remote XPDR then you also have option to move it aft.

Carl

 

[BobTurner]

As Carl replied above, split mode operation is tough enough even if one antenna is on top and the other underneath. If copilot is listening while pilot is transmitting, you’re asking that poor radio to reject a 5 watt signal just a few feet away while cleanly bring in a micro-watt level signal from miles away. I personally wouldn’t even attempt it.

 

[rocketman1988]

I have both com antennas beneath the passenger seats on my -10. Have never had any issue with communicating on the ground or in the air. I routinely listen to com 2 while com 1 is active and have had zero issues. I am running a Garmin G3X Touch suite, GTN650, and a Garmin remote com two.