David W. suggested I use my RTL-SDR dongle to look for the source of the 40 meter RFI that I have been mentioning. (It appears as an ugly stipe in the waterfall of my Hodgepodge transceiver.) So I fired up the RTL-SDR — there were the tell-tale spikes, spaced neatly every 50 kHz. The ARRL Handbook says this is typical of a switched power supply. Before I started patrolling the neighborhood with a tin-foil hat and a portable receiver, I decided to check my own house for any recently installed electronic devices. It didn’t take long — when I unplugged the new (mid-pandemic) treadmill the spikes disappeared. This treadmill was located about ten feet above my rigs, and between the rigs and the antenna. Duh. I should have thought of this earlier. Mystery solved. Thanks David.
I like the Leviton 1470 switches – allows me to turn off stuff that doesn’t have an on/off switch !
Wireless power switche are even better! For lazy people like me. 🙂 Remote or wifi. (Phone, Google Assistant, or Alexa driven)
Just confirms the harm that exercise can cause. Dean KK4DAS
Even with the device powered off through the switch you were seeing the interference? I have witnessed some badly made electronics that ‘leak’ from the ground and give spikes like this.
I’m happy to hear that my suggestion pointed you to the path of success and not perdition.
No, the RFI disappeared when I turned the switch off.