Softrock RX/TX Ensemble – receiver

My previous two posts are about the Softrock RXTX Ensemble board, and getting it built. After I got mine built, I had trouble finding software applications to use it. Applications are out there, it’s just that I couldn’t find them. I’d be really happy to have something like Flexradio’s PowerSDR available for Linux. That application is great and it’s open source, but it’s Windows only.

(I’m definitely open to advice here, from the Linux SDR people who find this)

I’ve ended up being able to use an application called “quisk” as a receiver, but it required some customizations. My work was all done on Ubuntu Lucid 10.04.

This is not a solution you can just install and run, so be warned. You’ll have to twiddle with it, especially with respect to how your sound devices are configured.

Also, in order for this to work, you will have to have previously installed usbsoftrock as described in my last post, and it will have to be on your default path. This is because quisk starts usbsoftrock in the background to control the SDR board.

When I went looking at quisk, I found an older version on the yahoo softrock group which had been modded to work with the softrock, but it didn’t work for me. I ended up grabbing the latest version of quisk (3.4.8) and copying and modifying some files from the one that was on the yahoo group files area.

Grab quisk from the link above, then also grab this tarball containing two files.

Put the file named quisk_hardware_vk6jbl.py in the directory with the rest of the quisk source. Copy the file named ai4qrdot.quisk_conf.py to $HOME/.quisk_conf.py

At a minimum, you will probably need to edit .quisk_conf.py to set your audio input and output devices. Quisk will receive audio on both stereo channels of the input (actually higher in range than you can hear, up to half the sampling rate). On my system, this is set like this:

name_of_sound_capt = “hw:0”

There’s a script in the quisk directory named portaudio.py, which will print information about sound devices – this may help you find the one you want. You’ll also need the correct input selected in the Ubuntu sound mixer, have it set to mic level, and adjust the volume there. Once you get this right, you’ll be able to see some noise (and hopefully signals) on the quisk display.

In order to hear the selected (tuned) output, you’ll have to have the output device set also. Now for me I was unable to listen on the speakers, which are the same device number as the input I’m using. I would get a split second of sound and then silence. I changed the output to be a pair of USB headphones I use, and that worked. For me, the USB headset device was selected like this:

name_of_sound_play = “hw:2”

A few other things to be aware of – If everything appears sort of ‘mirrored’ around the center of the display, i.e. you tune up in frequency and the signals you see shift up (right) instead of down, then you have the I and Q channels reversed, and need to swap them in these lines in the config file:

channel_i = 0

channel_q = 1

I hope that’s enough information to help. As I was doing it I didn’t really have in mind to document it, only to get something working.

It looks like quisk is capable of transmitting, using AM, SSB, or CW, but as far as I can tell it won’t handle PSK-31 and doesn’t make the audio available for other applications like fldigi. I could be wrong, I haven’t gotten into it very deeply. This may be possible using “jack” but I don’t know.

I’ve also only just discovered sdr-shell, and that looks like it does exactly what I want, with DttSP. In fact, I see that Bob McGwier was one of the starters of DttSP, which invokes full recursion.

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About Steve

I'm Steve Conklin, AI4QR I'm employed by Canonical, Inc as a Linux Kernel Engineer. Interests include Linux, open source software and hardware, electronics and music, and amateur radio.
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