Is it possible to test your antenna location before drilling??

AndyRV7 · #1 02-04-2020, 06:53 AM

I've saved the best for last...

I want to locate my ADS-B antenna just inboard of the passenger side fuel vent. This gives me 3 feet of separation from my transponder but only 2 feet from my comm. Is there any way to know if this will be a good spot before I drill a half-inch hole in the skin??

My other logical option is aft of the baggage compartment but the skin is thinner AND I have a historically greasy belly, which I've heard can degrade the signal. ...Not to mention the longer coax run.

Thanks for any advice. Andy

N941WR · #2 02-04-2020, 06:57 AM

I don't know about testing but my Transponder antenna went just inboard of my right fuel vent with no issues of any kinds. Being a taildragger, there was some concern the gear leg might block it but that has never happened in almost 1000 hours of flying.

When it came time to add the ADS-B antenna, I put it in the same location on the left side. Again, no issues, even though it didn't meat the minimum recommended distance.

One major advantage of these locations is that the wiring is really easy and they are out of the exhaust and oil streams.

flightlogic · #3 02-04-2020, 07:36 AM

The pulses at 978 mhz will not affect coms. Go for the shortest coax run.
Good ground at the base... and just wipe off oil now and then.

Pilot135pd · #4 02-04-2020, 08:59 AM

Quote:

Originally Posted by flightlogic

.. and just wipe off oil now and then.

oil prevents corrosion, just saying

flyer46 · #5 02-05-2020, 11:56 AM

That is exactly where I put my Echo antenna (just inboard of the vent). I tested it for you. It works perfectly at that location.

Walt · #6 02-05-2020, 01:06 PM

I would suggest you install per the manual guidelines or as close as practical to those guidelines.

Don't want to offend anybody but terms like "no issues", "works perfectly" etc. have no valid measurement basis and it's likely many of the locations that folks use, because it's convenient, give less than ideal performance (you just don't know it).
Just because it works doesn't mean it works as designed.

It's like any other antenna, you can stick em wherever you want (under cowl, wingtips, no ground plane, etc.), just don't expect them to perform like a correctly placed unit.

GalinHdz · #7 02-05-2020, 03:58 PM

Quote:

Originally Posted by Walt

It's like any other antenna, you can stick em wherever you want (under cowl, wingtips, no ground plane, etc.), just don't expect them to perform like a correctly placed unit.

EXCELLENT words of wisdom.

AndyRV7 · #8 02-05-2020, 08:20 PM

Quote:

Originally Posted by Walt

or as close as practical to those guidelines.

That could be a very big difference. Sadly, there are no perfect locations. I would guess most people aren't trying to find the simplest solution, but the best solution given their circumstances.

rightrudder · #9 02-05-2020, 09:00 PM

Quote:

Originally Posted by N941WR

I don't know about testing but my Transponder antenna went just inboard of my right fuel vent with no issues of any kinds. Being a taildragger, there was some concern the gear leg might block it but that has never happened in almost 1000 hours of flying.

When it came time to add the ADS-B antenna, I put it in the same location on the left side. Again, no issues, even though it didn't meat the minimum recommended distance.

One major advantage of these locations is that the wiring is really easy and they are out of the exhaust and oil streams.

My experience as well. My EchoUAT system aced the PAPR first time out.

This location gives a little more than a semicircle for a ground plane...and I was fully prepared to make it a full circle with foil on the underside of the cowling....but it proved unnecessary.