Using the TXEQ in PowerSDR-IFStage

[Karin]

I know that PowerSDR-IFStage was primarily written and modifed from the original PowerSDR software. As previously posted on this forum, I've made a lot of modifications to version 1.19.3.5 of PowerSDR-IFStage.  Primarily focused at a better user experience for the Elecraft K2, and also primarily for my own use.  I've not publicly posted any of these changes.  A few days ago a thought popped into my mind that there are some portions of the unused source code, mainly for the transmit functions which are still in the source code and still compiled in the resulting executable.  Normally one would select "RX only" in the setup page to disable the transmit related functionality of the code.  The thought I had was, how about using the TX Equalizer by routing a microphone input to the TXEQ input and using the output from the equalizer to drive the audio signal to the radio.  Since already had the audio paths established for digital operation (ie: FSK, PSK) from my computer to the radio, using the Windows mixer in the computer, I was thinking it would not be too much of a reach to figure out how to route the Microphone input from the Windows mixer to the PowerSDR TXEQ code then route the output of the TXEQ to the LINE OUT of the Windows mixer.  Now comes the difficult part, at least for me.  I've spent a couple of days trying to figure out audio setup and routing that PowerSDR-IFStage does.  I believe much of this code wasn't touched when Scott and company re-wrote the original PowerSDR v1.19.3.5.  Please corret me if I'm wrong.  Looking over the release notes in the source code I am making that assumption.  I'm still trying to figure out how the microphone input as described in the SDR-1000 instruction manual is routed to the audio paths in PowerSDR, and not having any success at all.

I'd very much like to communicate with anyone who might be interested in such a project, to better understand some of the architecture concepts related to the audio processing. 

 

     Regards,

      Karin Anne Johnson K3UU

[Scott M]

We didn't touch any code related to the transmit EQ.  -Scott

[Karin]

Thanks for the reply Scott.  I thought that was pretty much the case with regards to the software.  I've had some second thoughts about actually implementing this function.  It turns out I wasn't thinking very far ahead of myself, as the transmit bandwidth of an SDR transmit radio is very much determined by the baseband audio processing.  As I was thinking about this related to the Elecraft K2 or any other hardware defined radio, the transmit bandwidth is very much fixed by the usual crystal filter.  Excepting phasing type SSB exciters.  The TX equalizer wouldn't add much to the radio's performance in terms of "Quality Audio", to coin a term here.  It does turn out the audio paths within the SDR code are already there via the VAC functionality, if you can connect a microphone to the basic windows audio system.  It is a bit messy trying to use this with the K2, as some external switching is required to prevent feedback from the external LP-PAN which most folks use with radio to achieve the panadapter functionality that PowerSDR-IFStage was originally conceived. So for now I have a very good understanding of how the audio processing is integrated into the software via Callbacks.  A good learning experience for me but not something I think I want to pursue. Thanks again for the thoughtful reply.

    Karin K3UU