GPS Antenna

[rwarre]

Do GPS antenna go bad? Could figure out why my Auto Pilot wouldn't work while flying from Ind. to CO. yesterday. Discovered that my MGL Efis was not picking up any satellites and not referencing ground speed. Haven't check connections yet but thought I would throw this out first. Thanks

[OkieDave]

Check your connections first. Antennas are passive components and shouldn't go bad, though you might have a broken conductor in the cable or inside the housing (that's not the antenna itself going bad, but would still require replacement as it's beyond the skill of most people to fix, and frankly, not worth the time).

[KatanaPilot]

Garmin WAAS GPS antennas have an amplifier that can fail. We had a situation where one antenna failed and the RF it transmitted was strong enough to block the adjacent GPS antenna - so we experienced dual GPS failure on a G1000.

So not all antennas are passive.

[OkieDave]

Originally Posted by KatanaPilot

Garmin WAAS GPS antennas have an amplifier that can fail. We had a situation where one antenna failed and the RF it transmitted was strong enough to block the adjacent GPS antenna - so we experienced dual GPS failure on a G1000.

So not all antennas are passive.

I stand corrected. Mea culpa.

[Canadian_JOY]

I hate to sound persnickety however I can't let a factual error stand in the way of troubleshooting an avionics problem. Many GPS antennas are "active" antennas. DC power is fed up the coax cable to power an RF amplifier in the antenna. This amplifier can fail outright, or do other funny things like act like an active jammer for other GPS receivers.

The advice given in a previous post to check connections is always sound advice. Look and feel them - sometimes an errant shoe under the instrument panel can snag a coax cable and "poof" there goes your receiver! If the simple diagnostics don't work, you might be into a new GPS antenna "puck". Many of these devices used with EFIS systems are relatively inexpensive, certainly not like trying to pay for a Garmin antenna for a certified WAAS navigator.

[Canadian_JOY]

Aha! Somebody typed faster than I did! :-)