IQ balance correction

[bitglue]

Using a SoftRock receiver I get some pretty bad signal mirrors:

There's a blind optimizer available: http://cgit.osmocom.org/gr-iqbal/

In my experience it works pretty well, however it takes a little while to converge. And if it's not receiving input for a while (because you're transmitting, for example) sometimes it will converge with the channels reversed when it comes back. Also changing bands it has to converge again.

Some capability to adjust the balance for transmit would be good too. I don't know there's a way to automatically do this without some hardware with a loopback mode, but having some UI where I can tweak the correction factors automatically and save them for a couple bands would be a good start.

[kpreid]

Hmm. A use case for inserting optional blocks between a device and everything else. The device composition mechanism doesn't support that. Yet.