[aprssig] Help needed: APRS receive with RTL_SDR and Direwolf

[Heikki Hannikainen]

archive.org's Wayback Machine to the rescue:

http://web.archive.org/web/20190312004932/https://blog.pwarren.id.au/tech/2014/02/11/APRS-to-YAAC.html

On Sat, 17 Aug 2019, Greg D wrote:

> Thanks, Andrew.  Any clues would be helpful.
>
> The link times out, however.  No response.  Did he/she link to another
> document somewhere with the info?
>
> I've been poking at it some more, and part of the problem appears that
> the option '-E offset 0' is causing the audio output stream to be muted
> somehow on the RPi.  But not forcing the offset means that I'm not on
> the right frequency, as it appears to be picking up a nonsense offset
> from somewhere / sometime else.  I can fudge that with some reverse
> engineering, but direwolf still doesn't decode anything.
>
> Capturing the output from the frequency-fudged rtl_fm into a file and
> playing it on my PC does yield a packet signal, but it's badly
> distorted.  Need to find some additional controls.  So, making some slow
> progress...
>
> Greg  KO6TH
>
>
> spam8mybrain wrote:
>> Hi, Greg.
>>
>> One of the users of my software pulled this stunt to use an RTL_SDR
>> dongle. See if this (with appropriate adjustments) works for you.
>>
>> https://blog.pwarren.id.au/tech/2014/02/11/APRS-to-YAAC.html
>>
>> I make no guarantees; I haven't tried it myself yet.
>>
>> Andrew, KA2DDO
>> author of YAAC
>>
>>
>> -------- Original message --------
>> From: Greg D <ko6th.greg at gmail.com>
>> Date: 8/12/19 00:42 (GMT-05:00)
>> To: TAPR APRS Mailing List <aprssig at lists.tapr.org>
>> Subject: [aprssig] Help needed: APRS receive with RTL_SDR and Direwolf
>>
>> Hi folks,
>>
>> I'm trying to set up a "quick" receive iGate with a Raspberry Pi, an
>> RTL_SDR dongle, and Direwolf.  No joy as yet.  However, when I run the
>> SDR dongle as a server with rtl_tcp and aim GQRX at it with its internal
>> packet decoder tool, that decodes just fine.  Direwolf also works fine
>> with a USB sound card and a cell phone mike near my HT, so I'm guessing
>> the issue is with rtl_fm.  What setting have I bungled or missed in
>> doing this?
>>
>> The run string I'm using is this, or variations on the theme (I've tried
>> a bunch of different stuff, without luck).
>>
>> $ rtl_fm -f 144.39M -M nbfm -E offset 0 -g 11 -p 60 -r 24000 - |
>> direwolf -c direwolf.sdr.conf -r 24000 -p -D 1 -
>>
>> Here's what it displays.  Note the error from line 155 also is seen when
>> running Direwolf from a sound card, and that decodes just fine, so I
>> don't think it's a problem with the Direwolf config.  And, yes, it is an
>> old version of Direwolf, but for reasons too convoluted to go into here,
>> that's what I've got.
>>
>> Dire Wolf version 1.0a
>> Line 155: Missing tone frequency for space.
>> Audio input device for receive: stdin
>> Audio out device for transmit: null
>> Found 1 device(s):
>>   0:  Generic, RTL2832U, SN: 77771111153705700
>>
>> Using device 0: Generic RTL2832U
>> Channel 0: 1200 baud, AFSK 1200 & 2200 Hz, A, 24000 sample rate.
>> Note: PTT not configured for channel 0.
>> Virtual KISS TNC is available on /dev/pts/0
>> WARNING - Dire Wolf will hang eventually if nothing is reading from it.
>> Created symlink /tmp/kisstnc -> /dev/pts/0
>> Ready to accept KISS client application on port 8001 ...
>> Ready to accept AGW client application on port 8000 ...
>> Found Rafael Micro R820T tuner
>> Tuner gain set to 12.50 dB.
>> Tuner error set to 60 ppm.
>> WARNING: Failed to set offset tuning.
>> Tuned to 144390000 Hz.
>> Oversampling input by: 42x.
>> Oversampling output by: 1x.
>> Buffer size: 8.13ms
>> Exact sample rate is: 1008000.009613 Hz
>> Sampling at 1008000 S/s.
>> Output at 24000 Hz.
>>
>> Now connected to IGate server noam.aprs2.net (206.12.104.38)
>> Check server status here http://206.12.104.38:14501
>>
>> [ig] # aprsc 2.1.4-g408ed49<0x0d><0x0a>
>> [ig] # logresp KO6TH-8 verified, server T2BC<0x0d><0x0a>
>> [ig] KO6TH-8>APDW10:!3857.53N\12106.64W&
>>
>> and nothing after that...  Even with my TH-D74 in the same room, on EL
>> power so as to not crush the input.
>>
>> _______________________________________________
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>> aprssig at lists.tapr.org
>> http://lists.tapr.org/mailman/listinfo/aprssig_lists.tapr.org
>
>
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   - Hessu