Antenna separation

[Rupester]

Originally Posted by airguy

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.

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?

[airguy]

Originally Posted by Rupester

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.

[Rupester]

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.

[Carl Froehlich]

Originally Posted by Rupester

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

[lr172]

Originally Posted by Carl Froehlich

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

[az_gila]

Originally Posted by lr172

+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.

[Rupester]

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.

[maniago]

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......??????

[lr172]

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

[maniago]

Originally Posted by lr172

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?