GRT Avionics

I have my comm radios wired up and they are communicating with my 10.1 EFIS. The serial port is programmed and the counter is recording an increase. However I can't change the frequency from the PFD. I can change the channels on the screen but it does nothing to the radios and I can change the channels on the radios and it does nothing to the channels on the screen. Is there some setting I need to set or activate in order to get the remote tuning from the PFD to work?

I responded to your e-mails about this already but I will comment here for anyone else.

Radios controlled by SL30 or SL40 protocols are automatically configured for sending frequencies once the serial port is configured for SL30-1 or -2 or SL40-1 or -2. The "COM1 Device" and "COM2 Device" settings can also be set to make sure the EFIS knows what device is COM1 and what device is COM2. The SL30 protocol is mainly for NAV/COMs (and NAV-only units) like the original SL30. The SL40 protocol is for COM-only devices like the original SL40. From your e-mails it sounds like your M760Q only wants the SL30 protocol and won't accept SL40, which is weird since it's COM-only. There's currently no way to straighten that out in the EFIS software especially as you're already using the SL30 interfaces for actual NAV devices.

I've got the VAL COM2K and NAV2K connected to the EFIS. Frequency and volume controls appear to work fine. I'm working on tracking down an issue where the COM radio will work great until I complete a run-up, and then will only transmit carrier wave but no sideband information. I'm trying to determine if possibly there's something like an auto-squelch which engages with the higher engine noise and is then blocking out my mic output? I'm not finding any way described in either the Horizon 10.1" user guide or VAL COM2K install guide in how to adjust squelch.

The squelch is part of the volume control. When the volume control knob is active you can push the knob to toggle squelch on/off. If you push and hold the knob for a second it will switch to the squelch adjustment mode (SQL). The COM 2KR also has microphone gain and sidetone levels. Those are adjusted in SET MENU, Display Unit Maintenance, COM Settings.

Turns out my issues were other things like, incorrect antenna orientation, bad antenna wires, issues with poor grounding on shielded audio wire shielding, and an irritating style of old pin connections to the audio panel.
Various changes including swapping out the audio panel and many updates to the wiring solved the issue.
GRT ease of configuration really helped with swapping around which was COM1 and which was COM2, as well as just knowing that wasn't what I messed up on the initial install.