Symmetricom GPS for RTCM

This might be a stretch for the Allstar group, but figured if anyone was using one, I’d find them here.

We’ve had quite a few years of success using Garmin GPS 18LVC “pucks” feeding our RTCMs. Lately, it seems as mountain tops get more RF crowded, we are losing lock more and more often.

I developed a “gps distribution” board that can take either an RS232 or RS422 input and properly isolate and distribute the GPS signal up to 8 RTCMs at the same time (yes, we sites with that many, and are about to put up a new RX-only site with 11 RTCMs). I had hoped to use some old Symmetricom 58534A “nose cone” style outdoor GPSs’ at RS422 to A) get the GPS outside and B) utilize the RS422 to fight off interference on the line in. The setup actually works nicely, but I can’t for the life of my get the GPS to send the $GPRMC sentence. I have the original manual for the GPS, and I have the original HP software (SatStat) for monitoring/demoing/changing. I have 5 of these GPS’s from different eras (some Symmetricom and some HP, all same, just who owned the company at various times) and they WILL NOT respond to the $PFint sentences I send.

Is anyone else using these by chance? and if not, is anyone using an outdoor style GPS? If so, what model? what serial protocol are you bringing it back to the RTCMs with?

Thanks for sharing.


The Trimble Thunderbolt are commonly used as are the BG7TBL Units. See this ASL Wiki page. RTCM’s speak Trimble. The BG7TBL GPS speak Garmin at 9600 baud (as I recall). The Thunderbolt takes forever to boot.

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