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[picsig] RE: [aprssig] APRS tone encode question

Scott Miller scott at opentrac.org
Mon Aug 23 21:58:54 UTC 2004


I wouldn't trust that OpenTracker waveform too much.  I did that really
quick on my way out the door this morning without checking over the 'scope
config very closely.  I've done more detailed analysis with the RAL program
and it looks like a regular sine wave, with a couple of notches visible near
the peaks.  The 'scope was seeing this without any filtering, and it wasn't
a pure tone that was being measured - it was regular data and that always
seems to give it a weird look.  Plus, the time and amplitude scales weren't
set the same as in Andrew's picture.  This is the first digital storage
oscilloscope I've owned, and I'm still discovering that it doesn't give me
quite what I'd expect from an analog oscilloscope.  Maybe it's time to go
find the user's manual.  =]

I've had no trouble with decoding the OpenTracker data.  I  haven't really
run any controlled tests with various signal-to-noise levels to test it,
though.  Maybe someone can bring the gear for that to DCC and we can run
some comparisons.

Scott
N1VG

----- Original Message ----- 
From: "jtowler" <jtowler at xtra.co.nz>
To: <vk4tec at tech-software.net>; "'TAPR PIC Mailing List'"
<picsig at lists.tapr.org>; <scott at opentrac.org>; "'TAPR APRS Mailing List'"
<aprssig at lists.tapr.org>
Sent: Monday, August 23, 2004 2:36 PM
Subject: RE: [picsig] RE: [aprssig] APRS tone encode question


Guys,

Interesting that the original picture of the 3 bit resistor waveform and the
MX614 waveform both look sin-wave in shape, but that last one from
OpenTracker looks much more like a triangle shape. Very sharp looking peaks.

Real question: How well does each decode on typical receive units?

Just interested ... Not really too important ... Just interacting to pass
the time ...

Regards,
Jim, ZL1TYF





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