A bit of rx audio at start of transmission

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W1JA
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A bit of rx audio at start of transmission

Postby W1JA » Thu Jun 29, 2017 6:38 pm

I'm just getting started in digital modes. I followed, for the most part, WU2O's virtual audio tutorial (http://wu2o.dyndns.org/wu2o_vac_tutorial_2.html) section 8. (I say for the most part because I had to swap B1 and B2 on Voicemeeter Banana to get things to work.)

I'm starting off trying PSK31. Monitoring my transmit signal, at the start of each of my transmissions I hear a couple hundred milliseconds of the last audio I received, retransmitted. I can vary the level of this retransmission with RX1 AF, but that also controls the audio level to my digital-mode software.

I'm using VAC1 in PowerSDR mRX PS 3.4.1, Voicemeeter Banana, and DXLab WinWarbler. I've tried playing with latency settings and can vary the length of this retransmission slightly, but it's always there for about couple hundred milliseconds.

Any ideas?

73, John W1JA
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W1AEX
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Re: A bit of rx audio at start of transmission

Postby W1AEX » Thu Jun 29, 2017 7:48 pm

Hi John,

That's certainly an inconvenient feature! I wonder if some combination of the "delay" settings on the left side of the Options menu tab could possibly eliminate or at least minimize this? It kind of sounds like a buffer is holding onto some data and then dumping it when your transmission is started. My guess is that Scott - WU2O knows a way to clean it up!

Hope you get it running smoothly.

73,

Rob W1AEX

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Re: A bit of rx audio at start of transmission

Postby AB2EZ » Thu Jun 29, 2017 10:10 pm

If there is a source of delay (latency) in the receive audio chain... for example, wireless Bluetooth headphones... then you will keep hearing the received audio for several hundred milliseconds after the transceiver has switched to transmit.

It notice this when I use Bluetooth headphones to monitor the VAC audio output of my ANAN-10.

Anan => VAC => Voicemeeter Banana Virtual Input => Dell computer's Bluetooth network adapter => Bluetooth headphones

Stu
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W1JA
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Re: A bit of rx audio at start of transmission

Postby W1JA » Thu Jun 29, 2017 10:39 pm

Thanks Rob and Stu. Stu - I'm hearing the sound in another receiver, so it's definitely an actual part of my transmitted signal.

But, I should say I was hearing the sound in another receiver, because I believe I have fixed it. I drew an audio routing diagram and I believe there's an error in Scott's procedure. I have to keep the transmit path (WinWarbler tx audio out to Voicemeeter to VAC1 input) completely separate from the receive path (VAC1 audio out to Voicemeeter to WinWarbler rx audio in). I must use Voicemeeter's AUX path for one of these paths, and the non-AUX path for the other.

This means, Scott's procedure in step 4 that says "...assign PowerSDR VAC1 to Voicemeeter input and Voicemeeter Output" should instead say "...assign PowerSDR VAC1 to Voicemeeter input and Voicemeeter AUX Output." And in step 5, "...assign your digital mode program to Voicemeeter Aux input and Voicemeeter Aux Output" should say instead "...assign your digital mode program to Voicemeeter Aux input and Voicemeeter [delete 'AUX' here] Output."

I hope I'm not misreading Scott's intent, but I can say that it works great now with the changes I have shown above.

73, John W1JA
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w-u-2-o
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Re: A bit of rx audio at start of transmission

Postby w-u-2-o » Fri Jun 30, 2017 1:24 am

John,

You are misreading my instructions. Because you swapped B1 and B2, that is why you are forced to swap the Voicemeeter and Voicemeeter Aux I/O settings.

This is what it should look like--I just confirmed this by using this configuration to have a digi QSO with Fldigi:

Image

Using this configuration, the ONLY source of TX audio will be from the digi mode program attached to the Voicemeeter Aux channel connections.

Now, that said, I've only validated this setup with Fldigi, PC-ALE, WSJT-X, Winlink Express, N1MM, MMTY, FreeDV and a few other odds and ends. I've never tried Winwarbler. Perhaps there is something different about the way Winwarbler works?

Note that, when you have the problem of RX audio in the first 100mS or so of a transmission, that is an indication that the digi mode program in question is somehow feeding RX audio through to its TX path and keying the radio before its RX audio buffer is empty and TX audio has started to flow. None of the programs listed above that I've validated has a capability to do that. However, a quick perusal of the Winwarbler documentation shows that it has some rather complex soundcard/sound interface capabilities. I'm not predisposed to installing Winwarbler, however you might take a more detailed and careful look at how Winwarbler is set up and restrict it to use only the Voicemeeter Aux I/O on a single TX/RX pair.

73,

Scott
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W1JA
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Re: A bit of rx audio at start of transmission

Postby W1JA » Wed Jul 05, 2017 12:43 am

Scott,

You are correct that I broke things by reversing the B1 and B2 selections on the VAIO and AUX input strips. I did that because of one of my OCD compulsions: Whenever there is a left-right pairing, I want to put receive-related things (VFO A, RIT, VMB rx audio metering...) on the left, and transmit-related things (VFO B, XIT, VMB tx audio metering...) on the right. I thought that I could just swap B1 and B2 to do this, and of course I was wrong.

But I can also be right. I can have it my way. By setting up PowerSDR VAC1 and digital software virtual input and output selections as I indicated in my changes to your procedure in my previous post above, I can have rx audio on the VAIO (left) input strip assigned to B1, and tx audio on the AUX (right) input strip assigned to B2. Then the B1 output (on the left) will be rx audio and the B2 output (on the right) will be tx audio. My symmetry needs are satisfied!

73,
John W1JA

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