[brettt777]

If I have RS232 data to my GTX-327 from the G3X for altitude, shouldn't that qualify as ADC data and therefore be enough for my auto-standby function to work? It says that it looks for GPS ground speed first and then ADC data.

 

[Longez]

Absolutely. This works great in my G3X aircraft.

Page F-4 of Rev. E of the G3X installation manual defines the wiring from the GSU-73 to the GTX-327 transponder.

It also includes the following configuration information for the GTX-327 (which you have probably already done):

GSU 73 TO GTX 327
A. ON THE GTX 327 CONFIG MODE PAGE, SET THE CONNECTED GTX 327 RS-232 INPUT FORMAT TO "REMOTE"

On the GTX-327, also make sure it is configured for "Automated Airborne Determination". If you have any trouble figuring out how to do this, come back and ask here and I will dig up the instructions.

From GTX-327 Manual:
Automatic ALT/STBY Mode Switching
If the GTX 327 is configured with Automated Airborne Determination, ALT mode selection occurs when lift-off is sensed. When the aircraft is on the ground, the transponder automatically selects and displays STBY

 

[Longez]

I looked in the GTX-327 installation manual and found some additional information. On the second configuration page is a selection called "Auto Standby". Make sure this is set to "ON" instead of "OFF".

Let me know if this configuration change doesn't make the Auto Standby feature work correctly.