Re: Interesting "source" of RF interference


The traditional sovereign cure for audio hum is 1 or more 1:1 audio transformers. It means you have a ground loop with non-negligible mains current on the shield connection of the #)*$)**&@##^ single ended pointy thing plugs and their sockets.

Treating the ends of the cables feeding inputs to devices treating the single ended wires as if they were balanced can also work. But that means RF problems will appear as you have to unground the socket and feed the socket's ground to the input of a differential amplifier. That's a lot more work so I've never really done it.


On 20220101 07:54:01, HERB KEATON N2GEW wrote:

Happy New Year to All!
Perhaps not as "interesting" (but certainly an RFI source to be reckoned with) is my shack computer speaker system. It happens to be an Asus Desktop with a
Dell 5.1 powered speaker system into the Realtek HD Audio Manager. Upon turning the speaker system on, I have always detected a low and slight "hum" associated
with these speakers, but easy to ignore as it is only detectable when the speaker volume is extremely low.

Whether that "hum" is associated with the RFI or not is indeterminate. But take a look at 14290 Khz and 7150 Khz approximately. 

Note, the easy workaround is to turn off the system. See 10.02.28 when I turn off to 10.02.34 turn on: the 40-meter screen shot. I don't have to 
unplug anything, just shut off the speaker system. 

I will look at eliminating this in more depth moving forward.


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