The curious case of the wandering audio output

[VK2CSW]

I have a curious case of wandering output power on WSJT-X and my FT-857D which the sleuths here may be interested in...

It was a dark and stormy night.

A little while back I upgraded the laptop I use to run WSJT-X to Windows 10.

The upgrade from Windows 8.0 was long overdue and was prompted by several apps I use no longer offering support on Windows 8.  JT-AlertX was the straw that broke the camel's back.

The upgrade was not without issues but after a few hours farnarkling about a workable platform was in place.

So off to the shack and onto FT-8.  Over the last few weeks I have noticed that I have to keep an eye on both my output power and ALC meters while the system is transmitting.  The output power wanders, sometimes up and sometimes down without any knowing changes from me.

An adjustment of the PWR slider and all settles for a while.

I suspect that the Win10 audio driver and built in audio card may be causing the wander.  Prior to the OS upgrade the driver had both the windows driver and a OEM driver for the sound card, there is no longer a Win10 OEM driver available, so the Windows driver is the one in use.  It recognises the card and seems to (otherwise) operate correctly.

I am awaiting an el cheapo external USB sound card, well a $20 one - not the $4 one.  The thought is to move the audio I/O that WSJT-X is using onto the external card to eliminate the Win10 driver and internal card from the set up.

Has anyone come across this before?

I can understand the output audio (and therefore power) changing slightly as the output frequency is moved up or down the spectrum this being a function of the generated tones vs the frequency response of the sound card but the wandering happens without any such change.

[VK5TM]

You could try loading the Win 8 driver to see if it cures the problem (Win 10 will run quite a few Win 8 drivers).

Hopefully it wont try to self update to the Win 10 driver.

[VK2CSW]

Well it looks like it might well be a moot point.

I realised I had a USB audio interface I could experiment with -a USB mixing desk- so wandered out to the shed.

It looks like the NBN FTTC Modem that was installed on Friday is simply a source of Wideband Noise on the HF bands. The waterfall is hundreds of thin vertical lines.
Power the modem down or unplug it from the lead-in and magically it goes away.

The NBN isn't even fully installed and is already causing issues.

I didn't get around to testing the audio interface.

[VK4ADC]

If it uses a 'plugpack' power adapter (wall-wart), it could be that. Just a thought.

[VK2CSW]

Hi Doug,

Unfortunately not. As the FTTC modem back powers the switchgear in the street it takes 240v straight into it. A good idea though.

Made me think of what else is new.

The router and a coffee machine - sadly none of them are the culprit after powering them down.

[VK4ADC]

Worth trying clip-on ferrites and/or passing all power leads through toroids multiple times.

[VK2CSW]

I have put a couple of toroids on the 'phone cable' that is the FTTC data cable - a small improvement.

But due to the design of FTTC it uses the existing telecom house wiring - that means unterminated wiring all over the house. I can't see anything but trouble from that design...