This worked for me gps to 436hp
There was a u Tube video posted several years ago of a person connecting his gps to his Home Patrol. Here is the link:
https://www.youtube.com/watch?v=uWVdh2Docx8
So I bought a used Garmin etrex vista on ebay ($44), and purchased the Garmin serial port connector (PC interface cable (RS232 serial port connector) ($29). I then connected it to the serial port cable/plug from my Uniden 396xt through a serial gender changer and null adapter. I set the Vista's interface settings to NMEA in and NMEA out, and the baud rate at 4800. I set the baud rate on the 436HP to 4800, and connected the Vista to the HP via the serial port.
Once the Vista gps acquired the satellite data, it was apparently read by the HP, just as it was from my cigarette lighter powered Uniden gps unit. The HP changed sites and transmitters according to my physical position as I drove around exactly as it did with the powered unit. I was also able to walk around with the setup, which, of course, was not dependent on an external power source, other than the AA batteries in the Vista gps.
The downside to this set up is that Garmin does not make a serial output gps unit anymore, nor do the current models support NMEA/ serial output, so you have to find a used unit (there were several old garmin units that would work, according to their specs).
This worked for me. I am guessing that there might be a market for a small battery powered gps "hockey puck" to run with the current run of HP location based scanners. Of course, I expect that they are thinking of including a gps chip in the scanner itself, in some later iteration.
It was fun to try to work this out. Yea for the internet.