[App_rpt-users] Trouble with RTCM and Garmin GPS (18x LVC)

I can't get the RTCM to recognize the attached GPS unit. Reference: http://static.garmincdn.com/pumac/GPS_18x_Tech_Specs.pdf I have determined that pin6 on the DB15 of the RTCM is transmit data to the GPS (using an oscilloscope) and that's hooked to the RxData line of the Garmin (green). Will the Garmin respond if it does not have lock? RTCM diagnostics complain: Running Diagnostics... Warning!! VF Diode NOT calibrated!!! Testing PTT/External CTCSS Error - Failed to read PTT/CTCSS in asserted state Testing GPS UART Error - Failed to read data from GPS UART Any hints? or ways to get more diagnostics? -Doug-