[aprssig] GPS to TNC APRS packet processor

Andrew Rich vk4tec at tech-software.net
Fri Mar 17 21:19:56 CST 2006


A while back I was playing with a PIC and I thought I would have a go at
making it do RTTY.

I was surprised at how well the thing actually worked.

I was expecting harmonics and all sorts of problems.

I used a Resistor ladder of 4 bits.

I hooked it up and the thing copied 100%

Ok so I started to introduce noise and the thing still copied 100%

It is amazing what these little chips can do.

Maybe one day we will have PIC based modems.

One chip - then we will have to work on modulation techniques.

Ok going to fire up my open tracker here and play with your new PSK code.


Andrew Rich
Amateur radio callsign VK4TEC
email: vk4tec at tech-software.net <mailto:vk4tec at tech-software.net>
web: http://www.tech-software.net

-----Original Message-----
From: aprssig-bounces at lists.tapr.org
[mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Wes Johnston
Sent: Saturday, 18 March 2006 12:53 PM
To: TAPR APRS Mailing List
Subject: RE: [aprssig] GPS to TNC APRS packet processor

Scott, what is your guess for a price on the T2 kit?  I have a SCSG meeting
in the morning, and would like to "rough" them in when telling them about

----- Original Message -----
From: scott at opentrac.org
To: 'TAPR APRS Mailing List' <aprssig at lists.tapr.org>
Sent: Fri, 17 Mar 2006 16:04:12 -0800
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
> 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
> 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
> more than a regular OT kit, though.  And I haven't written the software
> 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
> _______________________________________________
> aprssig mailing list
> aprssig at lists.tapr.org
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