[aprssig] Help needed: APRS receive with RTL_SDR and Direwolf
ko6th.greg at gmail.com
Sun Aug 18 14:12:15 EDT 2019
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!
Heikki Hannikainen wrote:
> archive.org's Wayback Machine to the rescue:
> 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
>> 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.
>>> 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
>>> 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
>>> 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
>>> 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
>>> 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 (126.96.36.199)
>>> Check server status here http://188.8.131.52:14501
>>> [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
>> aprssig mailing list
>> aprssig at lists.tapr.org
> - Hessu
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