22-06-2018, 05:38 PM
I did some more chasing this afternoon while the house was otherwise unoccupied (for the sake of household harmony).
The power lead has already had 2 x clip on ferrites and for extra surety, today, I've put third clip on ring type with three turns of the lead through it.
I will need to recheck my tests, although I repeated them a few times, it doesn't make sense to me.
To test I set WSJT-X to call CQ and allowed it to run through either 4 or 6 transmitting cycles. I then ducked into the lounge to monitor the soundbar.
First test was to see if changing bands or antennas made a difference. Tried 40m, 20m and 10m via my 20m 1/2 Wave Dipole. Nothing seen on 10m but given the mismatch with the antenna, I am not sure that proves anything as I have no idea how much RF was going out. Both 20 and 40 caused the issue.
I have a G5RV Jnr strung up inside the roof cavity. This is much closer to the soundbar. Both 20 and 40m showed the gremlin.
Next up, I tried earthing the soundbar. As it is double insulated it was non-trivial, but I ended up grabbing the USB maintenance port shield which buzzed out as connected to the small areas of chassis accessible. It made exactly zero difference.
Now for the weird bit, I thought I would go back to the simplest form I could, as the soundbar has two physical inputs (power and optical signal), I disconnected the optical cable from the sound bar. I set WSJT-X doing it's thing. It ran for two full minutes and nothing.
WEIRD.
Not trusting the result I reconnected the optical cable. RFI was back. Once again I disconnected the cable and it went away.
I reconnected the cable to the soundbar, but this time disconnected it from the TV. At first no RFI but on about the third cycle there it was.
At this point I would normally call it that the problem is coming in via the optical cable, except I really don't understand how it is possible.
So my new to do list is:
1. Redo the tests (I simply don't trust the results);
2. Replace the optical cable with a different one and retest;
3. Try linking the soundbar via HDMI and retest (this seems illogical to cure RFI); and
4. If all that fails take up Lawn Bowls because this is making my head hurt
Is there any point in putting ferrites on the optical cable?
The power lead has already had 2 x clip on ferrites and for extra surety, today, I've put third clip on ring type with three turns of the lead through it.
I will need to recheck my tests, although I repeated them a few times, it doesn't make sense to me.
To test I set WSJT-X to call CQ and allowed it to run through either 4 or 6 transmitting cycles. I then ducked into the lounge to monitor the soundbar.
First test was to see if changing bands or antennas made a difference. Tried 40m, 20m and 10m via my 20m 1/2 Wave Dipole. Nothing seen on 10m but given the mismatch with the antenna, I am not sure that proves anything as I have no idea how much RF was going out. Both 20 and 40 caused the issue.
I have a G5RV Jnr strung up inside the roof cavity. This is much closer to the soundbar. Both 20 and 40m showed the gremlin.
Next up, I tried earthing the soundbar. As it is double insulated it was non-trivial, but I ended up grabbing the USB maintenance port shield which buzzed out as connected to the small areas of chassis accessible. It made exactly zero difference.
Now for the weird bit, I thought I would go back to the simplest form I could, as the soundbar has two physical inputs (power and optical signal), I disconnected the optical cable from the sound bar. I set WSJT-X doing it's thing. It ran for two full minutes and nothing.
WEIRD.
Not trusting the result I reconnected the optical cable. RFI was back. Once again I disconnected the cable and it went away.
I reconnected the cable to the soundbar, but this time disconnected it from the TV. At first no RFI but on about the third cycle there it was.
At this point I would normally call it that the problem is coming in via the optical cable, except I really don't understand how it is possible.
So my new to do list is:
1. Redo the tests (I simply don't trust the results);
2. Replace the optical cable with a different one and retest;
3. Try linking the soundbar via HDMI and retest (this seems illogical to cure RFI); and
4. If all that fails take up Lawn Bowls because this is making my head hurt
Is there any point in putting ferrites on the optical cable?