GNX 375 intermittent GPS signal loss

[jbDC9]

Just checking to see if anyone else has run into this issue...

I have a new install GNX375 in my RV-8 that seems to have a glitchy GPS receiver, or something... it will intermittently and randomly lose the GPS position signal for a bit, usually between 5-15 seconds, then it reacquires the signal. The antenna is mounted on the rear turtledeck with new RG400 cable running under the left side floorboards and through the gear tower to the panel. The TNC connectors check out ok, no shorts that I can see. I swapped in a good known replacement antenna to see if that were the issue, but the problem persists, so it's not the antenna.

From the Install Manual:
6.4.1 Antenna Location
The GPS antenna should:
1. Be installed as near to level as possible with respect to the normal cruise flight attitude of the aircraft.
2. Be installed in a location to minimize the effects of airframe shadowing during typical maneuvers.
3. Be installed a minimum of two feet from any VHF COM antenna or any other antenna which may emit harmonic interference at the L1 frequency of 1575.42 MHz.
4. Be installed a minimum of two feet from any antennas emitting more than 25 watts.
5. Be installed a minimum of nine inches (center to center) from other antennas, including passive antennas such as another GPS or XM antenna.
6. Be installed a minimum of three inches from the windscreen.
7. Have a twelve inch center to center spacing between GPS antennas.

All of these requirements are met. The transponder and ADSB side of the 375 are working fine, no issues there. Is there a data log that I can download and maybe send to the Garmin guys to see if they can find the cause?

I really want to like this unit, but this GPS unreliabilty, plus the Bluetooth doesn't connect to my Samsung/Garmin Pilot tablet, plus the MapMX flight plan transfer to/from the Aera 660 is buggy... it's frustrating.

Has anyone else run into this?

[BobTurner]

Set the receiver to the ?satellite? page and have someone watch it, on the ground but in the open so it sees the satellites. Go around and push and pull, gently, on the coax and connectors (especially where the coax goes into a connector). See if that isolates the problem. I know when I assembled a TNC I didn?t push hard enough to snap and lock the center pin. The cable tested good, but wouldn?t make good contact when inserted into the female connector.

[DeeCee 57]

Has anyone else run into this?

Nope, working perfect under good ol ?friendly? European skies

[dlloyd3]

I have a KX165 when keyed on several frequencies would cause my 375 to loose the GPS. Notch filter fortunately cured that. Could an older comm radio be the problem?

[jbDC9]

Originally Posted by BobTurner

Set the receiver to the ?satellite? page and have someone watch it, on the ground but in the open so it sees the satellites. Go around and push and pull, gently, on the coax and connectors (especially where the coax goes into a connector). See if that isolates the problem. I know when I assembled a TNC I didn?t push hard enough to snap and lock the center pin. The cable tested good, but wouldn?t make good contact when inserted into the female connector.

Now that?s a good idea, hadn?t thought of that trick. Duh. Will give it a shot.

Originally Posted by dlloyd3

I have a KX165 when keyed on several frequencies would cause my 375 to loose the GPS. Notch filter fortunately cured that. Could an older comm radio be the problem?

Interesting... I do have an old KX-125 in the panel, but transmitting on it has no effect.