FireMedic_2009
Well Known Member
I have a friend with a Lancair 290. He has a GNX375 with the antenna installed under the fiberglass cowling. His plane was down for close to 2 years to have 4 cracked cylinders replaced. The plane has been flying a few months now and has noticed the gps drop off intermittently.
We have confirmed the satellites drop off with the mic is keyed between frequencies 118.0 and 122.0. He first noticed it when the Xcruise was engaged. But then last week it dropped three times within a couple of short flights. The last time it dropped when he turned from the downwind to base before he keyed the mic.
A month ago we tried a notch filter, physically grounding the gps antenna (it’s mounted on a small 12”x10” ground plane that’s grounded was already grounded) and the radio stack even though Garmin says a ground plane is not needed for the gps antenna. The Garmin tech went through possible radio interference, the elt’s electrical board possibly being activated during radio xmission. So we tried removing the elt and placing it in a trunk of a car to completely isolate it from any radio xmission while testing it on the ground. We even tested it away from any hangars, but the gps signal would still drop momentarily when the mic was keyed between those frequencies.
So what I’d like to try is placing his GNX375 unit in someone’s plane here in Florida to make sure it’s not the unit with the problem and rule that out. If the unit is not the problem then not sure what’s causing the problem. He is located in Tampa KVDF and can fly over to you
Thanks
Daren
We have confirmed the satellites drop off with the mic is keyed between frequencies 118.0 and 122.0. He first noticed it when the Xcruise was engaged. But then last week it dropped three times within a couple of short flights. The last time it dropped when he turned from the downwind to base before he keyed the mic.
A month ago we tried a notch filter, physically grounding the gps antenna (it’s mounted on a small 12”x10” ground plane that’s grounded was already grounded) and the radio stack even though Garmin says a ground plane is not needed for the gps antenna. The Garmin tech went through possible radio interference, the elt’s electrical board possibly being activated during radio xmission. So we tried removing the elt and placing it in a trunk of a car to completely isolate it from any radio xmission while testing it on the ground. We even tested it away from any hangars, but the gps signal would still drop momentarily when the mic was keyed between those frequencies.
So what I’d like to try is placing his GNX375 unit in someone’s plane here in Florida to make sure it’s not the unit with the problem and rule that out. If the unit is not the problem then not sure what’s causing the problem. He is located in Tampa KVDF and can fly over to you
Thanks
Daren
