gqrx with hamlib control of softrock usb-controlled soundcard radio on linux

[Roger David Powers]

I configured gqrx to use the sound card input being driven by the softrock radio which worked but gqrx was not able to control the radio.

I noticed gqrx was using SoapySDR's SoapyAudio module in this use case, and that SoapyAudio can use hamlib to control various SDR radios including Softrock.

I found I had to make some code changes to SoapyAudio to get this to work.  It seemed to be assuming that all hamlib radios were controlled via serial ports, which is not true these days.

Anyway I filed my notes and a code diff as an issue at the SoapyAudio page:

https://github.com/pothosware/SoapyAudio/issues/16

It gives the device strings I used to make this work from gqrx.

Sorry even though I am a SDR newbie I realize this is not very newbie friendly.  It seems you will have to apply the patch and build the module from source since it seems by default hamlib support is not enabled.  Yet it shows it can be made to work, and if the maintainers pick up the patch it will at least make it into the code base. 

Now I need to figure out why gqrx seems to be showing a mirror-image of the spectrum, mirrored around the center frequency.  I wonder if this is a FAQ. 

Regards,
RDP

[Simon Kennedy]

Hi RDP

I didn't think that gqrx supported audio input, are you using a specific SoapyAudio device string?

The image you are seeing can be caused by imbalance in the I & Q audio inputs.

Regards

Simon.

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[Roger David Powers]

Hi, Simon.

GQRX device string ends up looking like:

device="default_input=True,default_output=False,device_id=0, driver=audio,soapy=0,rig=2509,rig_rate=9600,rig_port=/dev/ttyS0

The last three things are the Hamlib control parameters.  The "driver=audio" part selects the SoapyAudio module.  

I believe the "soapy=0" part selects Soapy device 0 as seen via "SoapySDRUtil --find".

I will investigate I/Q imbalance some more, thanks for the suggestion!

Thanks!
RDP

[Roger David Powers]

EDIT: doing too many things at once...

I gave the strings for a failing use case.  The working GQRX string ends up looking like:

device="default_input=True,default_output=False,device_id=0,driver=audio,soapy=0,rig=2509,rig_rate=0,rig_port=/dev/rig

More info is in my write up at https://github.com/pothosware/SoapyAudio/issues/16

Sorry for the confusion.

RDP