Well, here's a problem that I induced upon myself. I bought one of those $200.00 APC UPS power back-up systems, which it very essential where I am. However, about every minute it pulses a charge to the batteries and that pulse rips into LF, MW, HF, and even into lower VHF. The fundamental FREQ seems to be on 67KHz with multiples there after. I've reduced those emissions with CAP's and chokes, but I can't believe that they would allow something that invasive to be sold on the consumer market. Well, then again, yes I can. However, it's not a warbble sound, but an AC BURRRRRRRRRRRRRRRRRRRRRRR sound that rips at + S60/9 at LF. I'm not saying that's what you have, but it's possible that someone bought a cheap UPS and you're hearing that from a few hundred yards away. Also, these new smart TV's radiate RF crap like crazy, even when off, which they never really are, but on a stand-by. If I remember, you still have an ATS-909 portable. You might want to take a walk with it and DF your source. That's what I've had to do with a septic UV light PS. It ripped a BZZZZZZZZZZZZZZZZZZZZZ throughout the entire HF spectrum and it's buried out in the yard. It has an RF invasive switching power supply and what I did (When I DF'ed it.) was to put a 1uF 400V CAP across the PS DC terminals and that worked great. So, I hear ya. This is an on going battle.
