Sunday, May 7, 2017

gqrx on freebsd

I'm still tinkering with my own SDR code in C, but I decided I'd give gqrx a go. It sports a simple UI to visualise things as well as a simple control network protocol.

FreeBSD has packages for it, so it really was as simple as:

# pkg install gqrx

I already have the rtl-sdr bits installed, so that was pretty easy:

# rtl_tcp

.. to bring up the network service for it.

But running gqrx .. didn't work. It just stood there and did nothing when I ran it - no UI, no useful log output, nothing.

So out came truss. Step one in the "what is going on" showed no useful logging. Step 2 is "ok, what syscalls is it making." It turns out it was trying to connect to the IPv6 localhost address - but rtl_tcp defaults on FreeBSD to IPv4 localhost. gqrx doesn't handle connect() errors gracefully, so it was just stuck in an infinite connect() loop.

So I cleared the config, started gqrx again, and ensured this time it was set to '' instead of 'localhost'. Voila! It worked!

Now - I need an SDR unit that can go down closer to DC so I can pick up shortwave. This RTL dongle I have doesn't tune below 27MHz.