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Blue750
09-19-2016, 08:03 PM
One of the restrictions for consideration when placing a GPS puck on the aircraft from the manufacturer of my GPS (Dynon GPS 2020) is to maintain 3 ft separation from any other transmitting antennas. In the location I would like to mount the puck, I have good separation from my top mounted VHF comm antennae, but the placement is within approx 1ft of my ELT whip antennae. Normally the ELT will not be transmitting inflight and if on the ground only in a crash type scenario. Does it seem reasonable to consider the ELT whip a "non-transmitting" antennae and therefore not a concern with regard to my GPS puck placement? What concerns would you have with the proposed placement? Thanks for all thoughts and or discussion!!

Dave
FlyingRon
09-20-2016, 06:25 AM
Yeah, I'd not worry about the ELT antenna. It's neither transmitting nor receiving in any operation you'd care about.
Blue750
09-22-2016, 09:57 PM
Yeah, I'd not worry about the ELT antenna. It's neither transmitting nor receiving in any operation you'd care about.

Thanks "FlyingRon" , I was concerned with interference from certain VHF freqs being reradiated thru the ELT antennae and possibly disrupting GPS signal. After a few queries to Dynon and an avionics shop, I am not as concerned as I was initially. Evidently antennae and electronic circuit designs have mostly eliminated the problem associated with older 121.5 ELTs creating an occasional issue with certain frequencies and the GPS. Not an issue with the newer 406 ELTs.
FlyingRon
09-23-2016, 07:45 AM
That is an issue with the crap output stage of ELTs but I'm not sure that the GPS-to-ELT spacing is going to make as much difference in that case as the comm-to-ELT spacing. The bigger issue is indeed of direct COMM-to-GPS transmitter interference.
Blue750
09-26-2016, 06:36 PM
Agree...but I am not as concerned as I was before researching and discussing it with brighter RF guys than me! Here is where I ended up mounting my stuff on top of the fuselage. Two more antennas to go (ADSB and XPDR) on bottom front of aircraft.

5805

Cheers! Dave