I no longer have a pressure altitude reading on my transponder and Garmin 430. I am not an avionics specialist so I am at a loss. I have dual GRT Horizon displays and may have configured a setting incorrectly when setting up my ADSB. I installed a UAT Echo and it was operating correctly. My question is if the GRT transmits the signal or is it from another dedicated device or signal? I get a message that says no input signal channel 1 on my 430 and no altitude on my transponder.