[aprssig] GPS to TNC APRS packet processor

Dave Baxter dave at emv.co.uk
Mon Mar 20 03:28:05 CST 2006

The only real advantage would be that the TNC could receive too.
Perhaps initiating a posit on behalf of a recipient.  Or, (subject to
display hardware being present) actualy display a message for the
mobile/portable opp'.  Hmmm...  Thinks...  Been done before, TH-D7 or

Maybe there are GPS's on the market that can display "user" messages.
If so, for a limited number of users, no doubt it would be a nice idea.

An interesting "Project" (a cut down Tracker or clone?) but not sure if
there would be a mass market for it.  As to different NMEA "Idea's".
True.  But, the basic information will always be spat out in the same
form.  After all, you can hang a GPS RX from just about whoever makes
them, and so long as you can get a NMEA string into whatever gadget or
software you have, it will get passed and processed as needed.  Just
that if you want course, speed and height, you need to detect and
process at least two NMEA sentences.  Now, at the moment, not many
"gadgets" can do that, can they?

Dave G0WBX.

> -----Original Message-----
> From: scott at opentrac.org [mailto:scott at opentrac.org] 
> Sent: Saturday, March 18, 2006 12:04 AM
> To: 'TAPR APRS Mailing List'
> Subject: RE: [aprssig] GPS to TNC APRS packet processor
> > Just wondering if anyone has invented such a device, 
> perhaps using a 
> > microcontroller of some sort, that would sit in between a GPS and a 
> > TNC so that TNC's which are not out-of-the-box stand alone tracker
> I don't think so, mostly because it costs just as much to 
> make one that does the same thing without needing a TNC.
> > and the TNC could take care of transmitting it.  Using a real TNC 
> > would have its advantages versus a TinyTrak, et al on HF since the 
> > method of carrier detection is by audio voltage.  On HF, I find it
> You can just add an XR2211-based carrier detect circuit to an 
> OpenTracker or TinyTrak.  The newest OpenTracker board I'm 
> working on (the Tracker2) is already in beta testing and has 
> a '2211 circuit built in.  It'll cost a bit more than a 
> regular OT kit, though.  And I haven't written the software 
> DCD code yet - white noise will trigger it right now.  That's 
> a 5-minute fix, though - there's already a flag that tells it 
> if the DPLL is synced, just need to feed that into the CD counter.
> I guess maybe using a T2 doesn't count as 'without a TNC', 
> though.  It's a TNC in itself, and will do KISS and operate 
> as a digipeater.
> Scott
> N1VG

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