Sound Card<–>Radio Audio Isolation

[VK4ADC]

Further progress, then a further setback (why do I do this to myself?)
....
But no.  The Mrs comes in a says the soundbar on the TV is going nuts - volume going up and down, changing settings etc etc etc.

Checked the obvious - VSWR is 1.5:1, my transmissions were being received so I doubt it was being overdriven, station earth is intact and bonded to mains earth.

The soundbar is linked to the TV via an optical cable, so I doubt that is the point of ingress.  I placed some clip on ferrites on the power lead with no change.

Time for more head scratching.

Colin

It is likely that the soundbar, despite being linked by an optical cable, is suffering what we used to call audio rectification issues - in this case rectifying the RF while on TX and causing DC level changes inside.  Does the effect happen regardless of the band you are transmitting on - or is the antenna in near proximity to the sound bar ? Is the power lead from a power adapter acting as an antenna (a few turns through a clip-on ferrite will prove this aspect) ??  This type of problem is not unusual but at least the problem is within your household so therefore resolve-able without bad neighbour issues.

I have an occasional issue on 20M with FT8 only when I have the triband yagi pointing over the top of the shack and 100W out on transmit.  Fortunately that direction is NNE and I seldom have to point it that way.

My issue is with the CAT control (CI-V actually since it is an Icom) of the radio. The frequency intermittently jumps because the CAT data is being corrupted despite using shielded CAT wiring.  Extra ferrites haven't made any real difference and I suspect that it is purely RF field strength effects.  It doesn't happen on any other bands on the tribander, on the 12/17M 2el yagi or either set of full-size multiband dipoles.  

The shack earth is a 1.8M grounding rod with about 300mm left protruding and connected to the angle aluminium bus-bar along the back edge of the operating table using LDF4-50 coax outer about 1.2M long end to end - so it is very direct. RG213 outer braid flyleads connect the computer, monitor, Icom CT17 CI-V adapter case, radios, coax antenna switches etc to the bus-bar so all are bonded together and to the ground. 

My current solution is to turn off CAT control in WSJT-X configuration as soon as it happens the first time simply by setting the model to None.  I know I will have to spend more time solving the issue properly but just haven't got to it as yet.  Maybe a USB-COM adapter (rather than a COM1: /CT17) is the answer - I have a couple of these but haven't yet tried one to see if that resolves it.

Hope your QRM effects all get solved soon.

73 Doug