PowerSDR mRX Transmit Audio Setup

w5wc
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PowerSDR mRX Transmit Audio Setup

Postby w5wc » Fri Jun 02, 2017 4:00 pm

This was Doug's original posting on the initial release of the new, more sophisticated TX audio processing capabilities. I have copied the entire thread from the original 3.4.1 release thread and edited it down to just cover TX audio setup--Scott

Transmit Profile Sharing

Therefore, to support this kind of TXProfile sharing, there is also a new button in the Setup - Transmit tab labeled "Export Current Profile." When clicked, it produces this kind of XML file containing only the currently selected Transmit Profile. The file will be stored in the same directory where your database.xml file is located, and given a file name that's the same as the exported transmit profile's name. You can then send it to another ham for import into their own database using the Import Profile button in Setup.

To summarize, the following controls in the Setup - Transmit tab support working with transmit profiles and databases:
1) The "Profiles" section at the upper left, where you can select which profile is the current one from your personal collection. This is where you can also save a profile you've just set up, under a new name, or delete one you no longer need.
2) The "More Profiles" section at the upper right. When you check the "More Profiles" checkbox, you get a scrollable list of additional default profiles that come with the installation. You can then bring the one you highlight (click on) into your own group of profiles (see #1) by clicking the "Include" button just below this list.
3) At the center extreme right side is a new button labeled "Export Current Profile" that you can use to export the currently active transmit profile (see #1) to send to someone or archive for yourself.
4) At lower left are three Database buttons that operate as before, except the "Import Database" function can now be used to import transmit profiles that were produced by the Export button - either by you or someone else. (These three buttons appear no matter what tab you've selected in setup.)

In addition to using Setup, you can select which of your saved profiles is to be used as the current (operational) profile in the main window using the pull-down list at lower right near the other audio controls, which appears when a voice mode (e.g. SSB, DSB, AM, or FM) is selected.

To export a transmit profile:
1) Click the Setup menu item to bring up the Setup window, and select the Transmit tab.
2) Select the profile you want to export using the "Profiles" pull-down list at upper left.
3) Click the "Export Current Profile" button at center, extreme right.
4) A file with the same name as the profile is written in your database directory

To import a transmit profile:
1) Click the Setup menu item to bring up the Setup window, and select the Transmit tab.
2) Click the "Import Database" button at lower left.
3) Select the database file containing the profile you want to import, and click OK
4) If the import is successful, you will be notified that the program will shut down.
5) Re-start OpenSDR-PowerSDR mRX PS.
6) The newly imported profile will appear as an additional choice in the Profiles pull-down list in Setup-Transmit.

New Audio Tools

Do you have a rack of expensive audio equipment that you use to process your MIC signal before feeding it into your radio? Do you run the digital equivalent, a Digital Audio Workstation (DAW), on your computer? Well, if so, you can certainly continue to do that. However, included in this release, we are providing some important audio processing tools that enable you to IMPROVE YOUR TRANSMIT AUDIO and INCREASE THE "DENSITY" AND AVERAGE POWER of your signal without requiring these external options. The new tools are primarily a Phase Rotator and a Continuous Frequency Compressor (CFC). Accompanying these advances are additions to the TX Profiles and enhancements in the TX Equalizer and in ALC Compression control.

Rob, W1AEX, has generously prepared a "CFC Quick Setup Guide" as well as two videos, one focusing on the CFC and another focusing on the Phase Rotator. Thanks Rob!!

The Guide and Videos can be found here:

Guide: https://github.com/TAPR/OpenHPSDR-PowerSDR/blob/master/Documentation/TX%20%20Audio/06-01-2017%20Revision%20-%20Quick%20Start%20Guide%20for%20the%20OpenHPSDR%20mRX%20PS%20CFC%20Audio%20Tool.pdf

CFC Video: https://www.youtube.com/watch?v=j84LuuI70O4

Phase Rotator Video: https://www.youtube.com/watch?v=NM2x2tk0UbY

Also, Scott, WU2O, has developed an excellent block diagram of the TX Chain for reference during setup. It can be found here: TX Chain

* Enhanced TX Equalizer


Equalizer frequencies are now operator-adjustable. Also note, that as it has been since the installation of the WDSP library a few years ago, this is a Continuous Gain Equalizer, NOT a multi-band equalizer. This provides smooth gain transitions across the spectrum as opposed to abrupt transitions at band edges.

* Phase Rotator

In some AM transmitters, it is possible to boost the peak output power by having an asymmetrical audio waveform (positive peaks greater than negative peaks) and modulating to greater than 100% on positive peaks while restricting to <=100% on negative peaks to avoid "pinch-off."

In other AM transmitters and in the case of our digital-up-conversion (DUC) SDRs, this is not the correct approach. We have hard-limits which cannot be exceeded, such as the dynamic range of the DAC. The application of an asymmetrical audio waveform, with positive peaks greater than negative peaks, cannot further increase modulation in the positive direction; it instead REDUCES average power. The correct approach in such cases is to make the audio waveform as symmetrical as possible, i.e., equal positive and negative peaks.

The Phase Rotator makes the audio waveform more symmetrical. It does so by shifting the phase of various audio frequencies by varying amounts, thereby changing the shape of the waveform away from the somewhat typical asymmetrical waveform of human speech. Experimentation and analysis show that a wide range of phase shift versus frequency generally tends to improve symmetry. This wide range leads to an implementation with multiple identical stages, where the total phase shift is the sum of the shifts obtained in each stage. The stages have a specified "corner frequency" where the phase shift of the stage is equal to one-half of the total that the stage provides at the maximum frequency.

While the above explanation focused on AM, note that this feature can be used to increase average power for any speech mode. Note also, however, that it could be detrimental for any digital mode that requires coherent phase versus frequency.

Controls are found on the new DSP => CFC tab in Setup.

* Continuous Frequency Compressor (CFC)

Many audio racks and Digital Audio Workstations provide "Multiband Compressors" which allow specifying different amounts of compression for different audio frequency bands. The CFC offers a superset of that concept where, instead of having multiple bands with constant compression in each band, the compression varies smoothly between frequency points at which it is specified. This concept is similar to the operation of the WDSP Equalizer function; however, in this case, we are varying the compression level across frequencies rather than varying the gain. A Post-CFC Equalizer is also provided as an integral part of this function to provide a final tailoring of the desired audio frequency spectrum.

Use of this function for speech modes can significantly increase the "density" and average power of the signal. Note also that use for digital modes may be detrimental, depending upon the nature of the mode.

Controls are found on the new DSP => CFC tab in Setup.

* ALC Compression Control

On the DSP => AGC/ALC tab, you'll now find an "ALC Max Gain" control. Adjusting the gain above 0dB (the default) has a couple purposes: (1) if NOT using COMP/CESSB, it allows you to set the CFC output to peak at ~0dB and still get some compression (which is often desirable) in the ALC stage, and (2) if USING COMP/CESSB, it allows you to get some ALC compression even though the output of those stages does not exceed ~0dB.

* CESSB Reminder

Just as a reminder, for quite some time we have had available a CESSB Overshoot Control function. This is yet another feature to increase average transmitted power at the same peak power. The CESSB algorithm was published by David Herschberger, W9GR, in the NOV/DEC 2014 issue of QEX. Dave's focus was on SSB transmission. However, in our implementation, we support its use in all voice modes. NOTE THAT A "LINEAR PHASE" TRANSMIT FILTER MUST BE SELECTED FOR THIS FUNCTION TO OPERATE PROPERLY.

This can be enabled on the Transmit tab in Setup. Note that COMP must be enabled (even at 0dB compression if you prefer) for this feature to function.

* New TX Profiles

Need some help getting all these new audio controls set up? Some TX Profiles are provided to give you some starting points. Specifically, courtesy of Rob, W1AEX, four new TX Profiles are included with the PowerSDR mRX application. These are:
- SSB 2.8_CFC (2.8k wide - very helpful on 60 meters)
- SSB 3.0_CFC (3.0k wide)
- SSB 3.3_CFC (3.3k wide)
- AM 10_CFC (5k + 5k for 10k total width)
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w-u-2-o
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Re: PowerSDR mRX PS 3.4.1 released

Postby w-u-2-o » Fri Jun 02, 2017 5:48 pm

All honor to Chris, W2PA, for the database import functionality! This is epic stuff, and a looooong time coming. Chris, you will not be paying for drinks if there are any other PowerSDR mRX users at the bar!

As for the new audio processing capabilities, this isn't just a minor improvement, folks. This is next level sh*t! With this new functionality, there is no other radio, radio software, or ancillary audio devices that can even come close to obtaining the kind of high quality, high performing audio now possible in PowerSDR mRX. With all due respect, not even the W2IHY units will come close. The only way you can get this kind of performance is to have a rack full of pro audio gear, or be using a top quality digital audio workstation application like Pro Tools. The "other guys" will be years catching up to this!

Now, that said, this sort of audio quality does not happen by merely pushing a button. And you can't just turn everything up to "11", either. These controls can be used for good or evil ;) You will need to study and experiment. Rob's videos and sample transmit profiles should help to jump-start you along that path.

73!

Scott
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w-u-2-o
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Re: PowerSDR mRX PS 3.4.1 released

Postby w-u-2-o » Fri Jun 02, 2017 5:54 pm

Here is the block diagram of the audio path:

Image
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w-u-2-o
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Re: PowerSDR mRX PS 3.4.1 released

Postby w-u-2-o » Fri Jun 02, 2017 5:56 pm

And Rob's videos:



A65BK
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Re: PowerSDR mRX Transmit Audio Setup

Postby A65BK » Tue Jan 09, 2018 5:40 am

Hi Team,

I started working regularly on air with my HB Hermes, after a lot of issues and rectification with the help of my "expert" friends like Scott. Martin, Kjell, Phil, John, Mike and some others.
Now I need to fine tune my audio profiles for SSB. I have B1 Mic and UMC22 USB interface . Mic input go to VAC thru VMB software.
Can you advice me the steps to use my recorded Audio Wave file to use with PSDR and experiment with my audio profiles ?
I can record my audio and prepare wave file using VMB. But dont know how to use it with PSDR !

73s
Prem, A65BK
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w-u-2-o
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Re: PowerSDR mRX Transmit Audio Setup

Postby w-u-2-o » Tue Jan 09, 2018 10:56 am

Prem,

I noticed that the link to Rob's video above was dead. I've updated it. Go to 08:25 and watch how Rob uses the Wave menu in PowerSDR. Be sure to record your wav file at 48KHz and with peak amplitudes similar to what you get from your microphone directly in PowerSDR.

73,

Scott
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Re: PowerSDR mRX Transmit Audio Setup

Postby A65BK » Tue Jan 09, 2018 5:48 pm

Hi Scott,

Thanks for reply.
All my audio devices set for 44100. Is this ok or any issue.
44100 setting was used to ensure all Digital mode software also run well. I have read somewhere as 48000 setting may not work with some software. Not sure!

Is the MON audio from PSDR is reliable reproduction and will be same as the one receiving at other end of on air QSO ??

73s

Prem
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w-u-2-o
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Re: PowerSDR mRX Transmit Audio Setup

Postby w-u-2-o » Tue Jan 09, 2018 10:53 pm

Everything, and I mean everything, should be set to 48KHz. Make sure all of your VAC and/or VMB audio devices are set to 48KHz in the Windows Sound Control Panel, both recording and playback. Restart. All mainstream digi mode software, including Fldigi, WSJT-X, MMTTY, Winwarbler, DM780, etc. uses 48KHz as the native audio sample rate, as does PowerSDR.

MON will be faithful as long as you have PureSignal turned OFF. Turn on PureSignal and you will also hear the predistortion.
K9RX
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Re: PowerSDR mRX Transmit Audio Setup

Postby K9RX » Wed Jan 10, 2018 3:32 pm

Scott,

Forgive my ignorance .... just to be sure I understand. So IF I want to use PS, which was one of the top of the list items for getting the radio, I can't "hear" what I sound like using MON - correct?

If the answer is yes then let me ask this: if I turn PS off and listen to my signal using MON is this what the guy at the other end hears even when I am running PS? And if so it would still mean I can adjust all the audio tools to my liking as long as PS is off while I'm doing it knowing that it will sound that way with PS on - only on the RX end.

If the answer is no - well I'll need to tackle that with a question(s) when I receive the response to the above.

Gary
K9RX
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w-u-2-o
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Re: PowerSDR mRX Transmit Audio Setup

Postby w-u-2-o » Wed Jan 10, 2018 10:51 pm

K9RX wrote:Scott,
Forgive my ignorance .... just to be sure I understand. So IF I want to use PS, which was one of the top of the list items for getting the radio, I can't "hear" what I sound like using MON - correct?

If MON is on and PS is OFF, then you are hearing what you sound like without any artifacts from predistortion. If MON is on and PS is ON then you are hearing what you sound like including predistortion.

If I turn PS off and listen to my signal using MON is this what the guy at the other end hears even when I am running PS? And if so it would still mean I can adjust all the audio tools to my liking as long as PS is off while I'm doing it knowing that it will sound that way with PS on - only on the RX end.
Essentially correct, not including any effects of the amplifier that can't be removed by PS and distortions caused by normal propagation, of course.[/quote]

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