Have you looked at: http://wiki.allstarlink.org/wiki/RTCM_Client#GPS Specifically, does this Garmin use 5V or 3.3V logic? I believe the RTCM uses 5V logic only (the VOTER) will do either. If your Garmin is 3.3V, it may have issues. Also, make sure the baud rate is correct, and it is configured to send the required NMEA sentences. Lee On Nov 16, 2017 12:40 AM, "Doug Kingston" <dpk@randomnotes.org> wrote: 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- _______________________________________________ App_rpt-users mailing list App_rpt-users@lists.allstarlink.org http://lists.allstarlink.org/cgi-bin/mailman/listinfo/app_rpt-users To unsubscribe from this list please visit http://lists.allstarlink.org/ cgi-bin/mailman/listinfo/app_rpt-users and scroll down to the bottom of the page. Enter your email address and press the "Unsubscribe or edit options button" You do not need a password to unsubscribe, you can do it via email confirmation. If you have trouble unsubscribing, please send a message to the list detailing the problem.