Does anyone know whether the Transponder in the Garmin GNX375 always automatically goes to active transmitting when unit is power on? I thought it had an altitude (or groundspeed?) trigger? Or is this something that can be selected through the config options? (I can’t find it in normal setup pages but perhaps it can be accessed through the installation config menu?)
Speed dependant, can be adjusted, see page 7-16 of the installation manual. Have mine set at 30kts, and that works fine.
That’s amazing thank you!
Can you confirm how you access that page? I think it is a combination of knob and home button press?
Might be easier if I upload the whole IM 
Dan legend thank you!
Assuming you are not in possession of the IM… Garmin only provide those on request, and since I have an avionics update foreseen for next month or so, had requested the latest version about a month ago. So here goes, welcome 
Further observations / question if anyone knows or has any ideas please!
Avionics master – ON then powers ON the GNX automatically – I believe this is normal and is a selectable part of the installation wiring pins
If you shut down by turning Avionics master – OFF without powering down the GNX via the home key, it then seems to restart the next time with the transponder already transmitting in ALT. If you power off first via the GNX home key with transponder in STBY, it then restarts next time with transponder in STBY still.
Do other people find the above behaviour? I am thinking it is good practice/proper to power down the GNX before turning avionics master off?
I am also thinking the logic is that cutting power to the GNX via the avionics master makes the GNX think it has had a power interrupt so it comes back on next time in a different manner?
MattL wrote:
If you shut down by turning Avionics master – OFF without powering down the GNX via the home key, it then seems to restart the next time with the transponder already transmitting in ALT. If you power off first via the GNX home key with transponder in STBY, it then restarts next time with transponder in STBY still.
If you have automatic ground/air switching configured, then it should come up in GND mode. Is there a reason to ever have it in STBY mode?
Do other people find the above behaviour? I am thinking it is good practice/proper to power down the GNX before turning avionics master off?
I never turn avionics off individually – I just flip the avionics master…
I’m still here
And believe it or not, I’m not sure what my 375 does… what I know is that I’m using only that avionics switch to power on, and shutdown all my avionics, on each flight.
I’ll try to remember and spy on my GNX to see how it acts on my next flight(s).
I am not sure about right now but in the past Garmin transponders could do auto AIR/GND switching only with a differential pressure switch.
The GPS GS based method never worked on the GTX330 I have.
Accordingly, mine remains ON the whole time. If I wanted it OFF, I would pull the CB.
The above behaviour I cannot confirm either way.
