[aprssig] How to pick a GPS receiver, was: cheap GPS puck

Sander Pool sander_pool at pobox.com
Sat Jan 21 13:46:07 CST 2012

Thanks for that Stephen, very handy. You are right of course that USB 
mice are virtually universally compatible as long as you have the 
correct drivers installed. With luck you already have Prolific or FTDI 
drivers and it'll work without any additional drivers at all.

That said there are some GPS receivers that have binary streams that 
have functionality beyond NMEA. SiRF chipsets have such a mode and it's 
conceivable that someone builds a GPS receiver (USB or serial) that 
defaults to this mode, making it incompatible with applications that are 
not set up for it. The GPS 18 I have for my asteroid occultation work 
for example was programmed by the vendor to switch to NMEA. Apparently 
it came in binary mode from the vendor. If your application requires 
NMEA, ensure your GPS puts NMEA on the serial port.

So I think the best advise I can give is to understand the capabilities 
of your software (expects NMEA on a serial port), the capabilities of 
your computer (has RS-232 or bluetooth or USB) and the capabilities of 
the GPS (TTL, RS-232, USB, BT, internal or external antenna) you are 
considering. Things aren't difficult but there are no true shortcuts.

I made the mistake of buying two RoyalTek RGM-3600 receivers without 
investigating them closer. Once received it was unclear if they were TTL 
or RS-232. Luckily they were RS-232 but the vendor didn't know. Then 
they turned out to be hard coded at 19200 baud which is too fast for the 
D710. Attempts to slow them down failed. I learned a lot about GPS 
modules in the process though. Interesting stuff :)

I just got my BR-355 and I'm ready to open it up. Should be interesting 
:) I'll take some pictures to share later if anyone cares. The plan is 
to put it inside the D710 head.


     Sander W1SOP

On 1/21/2012 2:23 PM, Stephen H. Smith wrote:
> . <http://www.curioustech.net/xport.html>
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