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

[Greg D]

Ha!  Got one packet to decode.  rtl_fm parameter -s 22050 seems to have
been the key.

Direwolf is complaining that the volume is too high, so will work on
that.  But progress made! 

Thanks,

Greg  KO6TH


Heikki Hannikainen wrote:
>
> 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.
>>>
>>> _______________________________________________
>>> aprssig mailing list
>>> aprssig at lists.tapr.org
>>> http://lists.tapr.org/mailman/listinfo/aprssig_lists.tapr.org
>>
>>
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>
>   - Hessu
>