[OZAPRS] Suitable GPS for HF APRS & SCS DSP Tracker ??

Andrew Errington a.errington at lancaster.ac.uk
Tue Sep 23 12:53:16 EST 2008

> I have an SCS DSP Tracker TNC with NMEA input for GPS. Its a simple 2
> wire interface, however my Garmin Etrex GPS NMEA output will not work
> UNLESS the GPS NMEA output port, is triggered with a voltage to "wake up"
>  its output chip. This is done to obviously save battery power for the
> unit. IF its connected to a PC it simply uses voltage from one of the
> RS232 COM port pins to "wake up" the chip and the GPS then sends the
> data happily to the PC. This cannot happen when it is connected to the TNC.
>  Apparently this great battery saving feature was only implimented on the
>  later Garmin Etrex models. So.....does anyone know IF the Garmin Geko 301
> or any other small compact battery powered GPS has the ability to simply
> stream NMEA data out of its port, without needing a trigger voltage, to
> activate its comms chip? TIA.


Can you wire up the Garmin so that the trigger pin is held 'high' (or the
appropriate state) to fake it as if it were connected to a PC?  Are you
sure it is a power-saving feature, and not simply hardware flow-control? 
I suppose it doesn't matter either way.

Aside from that, I can confirm that the Garmin Geko 201 "just works".  I
have one, and I have set the output mode to NMEA.  When I turn it on stuff
appears on the serial port.  When I turn it off, it stops.  (Yes, I know
you asked about the 301).

The Geko 201 is probably the most basic-but-useful GPS receivers you can
get.  The 101 is definitely not worth buying (and should never have been
made IMHO), and the 301 is not worth the extra money (it has a built-in
electronic compass and barometer, independent of the GPS-derived direction
and elevation calculations).




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