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11317Re: 10dB RX Level Shift after TX

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  • g4wjs
    Aug 18, 2013
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      --- In wsjtgroup@yahoogroups.com, "k0og" <counsil@...> wrote:
      > Greetings,
      Hi Joe,
      > I welcome the changes to WSJT-X v1.2 r3563, but find a bug was introduced.
      > When I opened it, after just running v1.1 r 3520, I found that the TX and RX levels had shifted, which was a surprise to me. I re-adjusted the levels with the sliders and it seemed to work well. Upon closing, then successive openings, I found that the TX level is consistent from opening to opening, but I find that the RX level is 10dB lower than the previous opening. If I transmit (either to carry on a QSO or just transmit a tune signal even with the radio turned off to eliminate RF problems), the actual RX level bumps up by exactly 10dB, but the RX level slide in WSJT-X does not move, nor do the Windows sound mixer sliders move. I have tried all the different settings in the configuration for transmitting into left, right, mono, or both audio channels, and none of the settings affect this 10dB jump.
      > To demonstrate this problem, do the following:
      > Open WSJT-X, then adjust the RX slider in WSJT-X for some level on the received noise (e.g., 40dB). Now, open the Windows mixer panel, recording panel, and just "touch" the input (in my case I use the "Line In" fader), and you will observe the RX level to instantly drop by 10dB. Go to WSJT-X and transmit a tune tone for a little bit (just one second or so is enough), and as soon as you go back to RX mode you will see the level jump back up 10dB to the original level.
      > So, it seems that some audio input level control in WSJT-X is unstable, and is altered by a TX operation.
      > Another observation is this: If you follow the above test procedure, observing the precipitous 10dB drop in input audio level, and simple close WSJT-X and then re-open it, it does the same thing as if you TX briefly, and the audio level jumps back up 10dB.
      I am not able to reproduce this but I only have a Windows 8 system and the control of audio levels in Windows changed considerably when Vista was introduced.

      It would be helpful if another XP user with different audio hardware, from your Creative PCI card, could verify this issue.

      Here's a little background. We have switched to new audio software, it is now done by Qt which is the framework that gives us a cross platform GUI. The switch was made to try and unify and reduce the number of external dependencies, it also fits better into the rest of the software. This has a few externally visible consequences like different names for the audio devices and slightly different behavior; for example most users are seeing different audio level settings with the new versions. It is quite possible that what you are seeing is another consequence, in this case not benign.

      Both the old and the new audio software we use are just a layer in the audio stack, in both cases the underlying audio service on Windows is provided by the Microsoft Wave Audio Services.

      The receive audio gain is implemented entirely within WSJT-X and doesn't touch any system audio levels.

      The tx audio attenuator uses a feature of the Qt audio framework. This may use the system audio level controls although I believe it only does that on UNIX, on Windows AFAIK it is implemented in the Qt framework software.

      So I think that perhaps on Windows XP there is some link between opening an output audio stream on a device and the input levels on that same device. This shouldn't happen and I'm not sure we have any control over it either Joe.
      > 73,
      > -Joe-
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