[OZAPRS] HF APRS tracker options.

Andrew Errington a.errington at lancaster.ac.uk
Sat Dec 6 10:29:49 EST 2008


Have a look at Mike Berg's pages:

http://www.ringolake.com/pic_proj/pic_index.html

I built a FreeTrak:

http://www.ringolake.com/pic_proj/gps_trak/freetrak202.html

(Ooh, it's a PIC16F628!)

It worked as advertised, but the rail-to-rail op-amp was tricky to find.

I, too, want to do APRS on HF, but I haven't yet tried it.  I looked
through the source code, and it seemed to me that it was very simple to
adjust the timing to change the baud rate to 300 baud, and to adjust the
tones.  The code already does MIC-E compressed, so that's ok for HF.  I'll
see if I can find my notes, and if you're willing to experiment then go
for it!

Since then I have heard that the op-amp (basically a unity gain buffer)
may not be necessary and that the audio in to the radio mic. can be driven
directly from the PIC output.  I have not verified this.  I also found
"NedTrak" which uses the same techniques, and uses an ordinary 741 or 358
op-amp:

http://pe1grl.khds.nl/nedtrak.htm

Good luck,

73,

Andrew
ZL3AME

On Sat, December 6, 2008 11:59, Steve wrote:
> G'day all,
>
>
> Can anyone provide some advice on APRS trackers for HF?
> I've been running VHF for ages now using various firmware versions (TT1,
> TT3 and my favourite - aprstracker) on the tried and true TinyTrak
> hardware, but it seems that only the TT3 firmware will support HF. My TT3
> tracker is in use in the car, so I don't want to rip it out to test HF if
> I can avoid it..
> As I wanted to get up and running this weekend, I'm looking for free
> tracker firmware that does 300bd, etc. Anything that will run on 16f84 or
> 16f628 type chips will be fine.
>
>
> Does anyone know of any options?
>
>
> Thanks in advance!
>
>
> Steve (VK2ZSZ)
>
>
>
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> Ozaprs at aprs.net.au
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>


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