====== Creating an APRS iGate with an RTL-SDR and Dire Wolf ======

**This is not finished yet, don't use!**

It's possible to create an APRS iGate using a relatively cheap RTL-SDR "dongle". As is common with SDRs they don't perform quite as well as a real radio, but they're a versatile tool that's worth having in the shack.

You'll need one with a Temperature Controlled Oscillator (TCXO) as the cheaper ones without drift too much for reliably decoding APRS. If you don't already have one I recommend the [[https://www.amazon.co.uk/Nooelec-NESDR-SMArt-SDR-R820T2-Based/dp/B01HA642SW|Nooelec NESDR SMArt]]. I also recommend //avoiding// the SMArtee version with it's inbuilt bias-tee unless you need one for a specific application.

Note that Dire Wolf also include their own detailed documentation [[https://github.com/wb2osz/direwolf/blob/master/doc/Raspberry-Pi-SDR-IGate.pdf|here]] but below is a quick summary to get you started.

===== Installation =====

Install the required packages:
  sudo apt-get install direwolf rtl-sdr
  
Create a directory for the logs:
  sudo mkdir /var/log/direwolf 

===== Configuration =====

When using Dire Wolf with an rtl-sdr it's necessary to edit the systemd service to ensure rtl_fm runs and redirect Direwolfs output into journald.

Open /lib/systemd/system/direwolf.service in your favourite text editor and replace it with the following:

<code>
[Unit]
Description=DireWolf is a software "soundcard" modem/TNC and APRS decoder
Documentation=man:direwolf
AssertPathExists=/etc/direwolf.conf
Wants=network-online.target
After=sound.target syslog.target network-online.target

[Service]
SupplementaryGroups=dialout audio
ExecStart=/bin/sh -c '/usr/bin/rtl_fm -f 144.8M - | /usr/bin/direwolf -c direwolf.conf -t 0 -r 24000 -D 1 -'
StandardOutput=journal
StandardError=journal
SyslogIdentifier=direwolf

[Install]
WantedBy=multi-user.target
</code>

Reload systemd, enable and start Dire Wolf
<code>
systemctl daemon-reload
systemctl enable direwolf 
systemctl start direwolf 
</code>

===== Usage =====

Starting manually:
  rtl_fm -f 144.8M - | direwolf -c direwolf.conf -r 24000 -D 1 -

View Dire Wolfs stdout:
  journalctl -f -u direwolf
  
{{tag>[rtl-sdr]}}