Antenna Ground Plane

For those of you who created an antenna shelf ahead of the firewall (mine is attached only to the engine mount, via adel clamps), how did you create the ground plane required of the antennas? The adel clamps, plus the powder coating on the engine mount, effectively isolate the shelf from the rest of the aircraft.

macrafic said:

For those of you who created an antenna shelf ahead of the firewall (mine is attached only to the engine mount, via adel clamps), how did you create the ground plane required of the antennas? The adel clamps, plus the powder coating on the engine mount, effectively isolate the shelf from the rest of the aircraft.

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OK, now I feel really dumb having asked this question. I knew the answer all along, just had one of those elderly mind blanks!!! As long as my shelf is large enough (8" in diameter in area, according to Garmin), I should be good. No need to ground the shelf to the aircraft. Sorry to bother ya all!

Just as a FYI, mine is adel clamped to engine mount and is nowhere near 8 inches in diameter and works just fine. I have another up on my glareshield with zero contact to any metal that also works fine. Have a hard time believing any ground plane is needed at all.

Erich

macrafic said:

OK, now I feel really dumb having asked this question. I knew the answer all along, just had one of those elderly mind blanks!!! As long as my shelf is large enough (8" in diameter in area, according to Garmin), I should be good. No need to ground the shelf to the aircraft. Sorry to bother ya all!

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if the shield of the coax is tied to the ground plane, you're good to go as long as the ground plane is large enough (sounds like yours is). Ultimately, it will be grounded to the A/C via your Garmin and the ground line back to the battery. I'd recommend that you alodine the ground plane, as least where the antenna mounts, to ensure a good electrical bond between the antenna puck and the ground plane once you torque down the mounting screws.

Uh, does the Garmin install guide say to install the GPS antenna on a ground plane? Quarter wave 'whip' antennas are the the only antennas typically used in a/c that need ground planes.

Charlie

I mounted a Garmin GPS antenna under the cowling on the RV7A without any kind of ground plane at all. Has worked great for over 10 years.

molson309 said:

I mounted a Garmin GPS antenna under the cowling on the RV7A without any kind of ground plane at all. Has worked great for over 10 years.

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Same here many times over.