I’m plagued with radio interference. Here I continue my efforts to rid myself of it.
The Elephant in the Room
Katie is obviously not an elephant, but she casts an elephantine shadow over shortwave listening at my house thanks to:
This system operates at a frequency of 10.7 kHz, which should be no impediment to shortwave radio listening, but it is in fact a notorious emitter of RFI, in my case between 5 and 7 MHz. I wrote a lot about it in my article, Killing the Noise. Spoiler alert: I didn’t kill the noise.
I did learn a bit about the little box in upper left of the picture above. It is a lightning/surge suppressor. It’s schematic diagram is not published (according to 6 AI services), but I doubt ot contributes any noise. It sits between the external AC power supply and the transmitter, and the screw terminals between the transmitter and the underground loop that surrounds my property. Like “The Force” as Obi-Wan described it, the loop “surrounds us and penetrates us” with that 10.7 kHz signal.
The local Invisible Fence installer suggested inserting an EMI filter between the invisible fence and the underground loop, a Corcom Model 10VK6. It was easier to get an equivalent product with the same schematic, the JSYUAN CS4L2-20A-S.
At this point, I do not know whether the EMI is primarily radiated through the house electrical system, the underground loop or the transmitter circuit board itself. If the new power supply (with some toroid coils) and the EMI filter don’t solve the problem, I’m looking to build a Faraday cage around the transmitter.
But wait
So I have a new, more sophisticated power supply for the transmitter from a Dell laptop, and I have an EMI filter. One might think that was all I needed, but there is a complication. The dog containment fence is not the only source of strong EMI. While the details change, turning off the fence still leaves massive noise behind, noise that wasn’t there last year.
Things always plugged in all the time at my house, while many, don’t change often. Unplugging a couple of new items didn’t identify the culprit, so I’ll have to be systematic about it. The plan is to turn off the dog fence (it has a battery backup and so has to be turned off separately) and then go through the electrical panel, circuit by circuit, turning each off until the noise abates. (One hopes it’s in my house and not a neighbor’s.) Then once that’s dealt with through replacement, it’s back to the dog fence.
This is why you see test results here and on my YouTube channel from “the Pond” or “the Park.”
The adventure continues with Killing the Noise: Part 3, Coming Soon.