I hadn't seen Tim's reply [below] to N4ZR's query when I sent mine out. I
hardly have any neighbors, much less security systems, near me but there's
certainly plenty of switching power supplies just in my own home. Which
reminds me to suggest to Pete that he check all the power adapters for any
laptops he has; I used to have 80m RFI from an older IBM laptop adapter.
From: Tim Duffy K3LR
I had a very similar warbler that we used to hear on 160 and 80 meters at
K3LR. Every 4 KHz. Using my Icom R1 handheld CW receiver, a step attenuator
and mobile whips I DFed the culprit. It was my neighbors security system. It
did not matter if it was "armed" or not. A W3NQN AC line filter on the
security system fixed the problem. I believe the switching power supply in
the security system was using the AC line as an antenna.
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