Antenna separation
 

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

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).

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

(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.)

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

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

IMHO this should be fine.

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

:cool:

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.

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.

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

Greg ..... does your UAT mfgr recommend 1 meter (or 3') between the ADS-B antenna and any others? It seems your separation from the comm antennas is well short of that. Also, which ADS-B box do you have?

I have the Dynon UAT (and Delta-Pop 978MHz blade antenna) - originally the 470, then the 472, and several subsequent beta-test versions of the 472. The installation requirements for the ADSB-472 antenna from Dynon specify only 2' (24 inches) minimum distance from the transponder antenna (which is fairly close in frequency) and no requirement for separation from comm antennae (which are very far away in frequency). The only problem I experienced with my antenna location was coax-related, when I replaced the coax my RF performance was excellent.

I'm not a EE, and I don't pretend to understand antenna theory - but I am of the understanding that separation of antennae becomes critical only when the operating frequencies are fairly close together. If I'm wrong about that I'm sure a few others will chime in to correct me - they always do - it's actually one of the traits I value most about this forum.

My separation distance between the transponder and the UAT antenna was a happy accident - during my early build I knew I would be nose-heavy due to other design constraints, so I was moving any equipment aft that could be moved. That included the transponder and its antenna - and they ended up residing just forward of the static port locations. The UAT came onto the market later and I was able to put that antenna under the seat pans between the comm antennae without any difficulties.

I have an Echo UAT to be installed in the next month (by moi) and I'm wrestling with the antenna location. Uavionics calls for 3' mininum separation from either xponder or comm antennas, which forces my ADS-B antenna back in the tailcone; and that, in turn, puts it further from the ADS-B box(es) than the 8' maximum they state for RG400. The lower loss coax options (primarily RG304 and RG393) are hard to find and terribly pricey. ($10/ft!) If I could get away with 2' separation, it simplifies my installation a bunch. :)

Can you just mount the ADS-B box in the tailcone near the antenna?

Carl

+1

No issue running the power and rs-232 lines all the way back there. Unit is very small and easy to mount about anywhere without structural support.

Larry

Yes, running four #22 wires vs. RG-400 co-ax is a no brainer. My -6A has about a 6 inch section of co-ax for the Dynon ADSB box and my -10 will be similar.

In both cases the boxes are aft of the baggage bulkhead.

Yes.... putting the Echo UAT behind the baggage bulkhead is an obvious alternative. I have (had, perhaps?) a desire to keep all my avionics up front, for ease of servicing and troubleshooting. Additionally, I have the GRT SafeFly which requires a GPS puck-GPSantenna connection also. That is most easily done on the glareshield. As always, it's time vs money for the insallation/retrofit. I may just pay the $10/ft for RG393. :)

Bent whip vs other antenna distances
 

When measuring out the separation from Bent whip antennas, do you use the tip of the bent whip or the base of the bent whip?

Theres no guidance on this that I've found, so I have to assume that everyone is using the base, even tho I think the correct answer is the tip.......or maybe the separation numbers already include a half foot for the assumed bent whip tip......??????

I believe you should have over 3' from UAT to transponder. I have the comms under the rear seats and put the UAT and transponder antennas under the front seats at the outer edges, just fwd of the gear legs. I have 3.5' between the two and over 3' from the Coms. If I have problems, I'll move the ADSb to the rear area.

Larry

Thanks Larry, but the actual distance is not the question.

The question is from where is the actual distance measured..........Bnc to Bnc connector?.......or some other point for measurement?

BNC to BNC should be fine. I would not however mount an ADS-B in antenna over the bent part as it is easy to find better spots.

90% of the bent whip energy is radiated in the first third of the antenna (the more vertical part).

Carl

Looks like I'll have to mount the echoUAT antenna about 10' aft of the firewall (I moved the GTX320A antenna about 7' aft of firewall to keep distance to 5.5' long muffler/exhaust pipe).

But if mounting the echoUAT unit in the aft fuselage, will the WiFi signal reach the cockpit (Nexus 7 tablet running iFly GPS and for configuration of the echoUAT.) ?

Finn