Another thought on the perhaps, but obscure file. We had laboratory ovens that had a "proportional" I believe, heater those pulsed on and off.

A Microwave Oven on certain settings will also pulse the Magnetron.

my first impression was, and still is, a swept beam, in azimuth as well as frequency.

This ties in with over-the-horizon radar, as the frequencies used are in the HF band to make use of the ionosphere, the beam is swept laterally to establish the target bearing, and by sweeping frequency you can establish target range, (comparing transmit frequency to received frequency to establish transit time = distance).

Still no idea who you could grumble to!

Harold

HAARP was fired up two days ago for an interesting experiment. Aimed at a passing asteroid with a high power HF beam, centre frequency 9.6MHz. Pulses every 2 seconds. Bounce from the beam was detected by many amateurs worldwide.

Many who recorded the reflections posted audio on the internet. Fascinating, not what I have been describing though, nevertheless, well worth reading about.

https://www.spaceweather.com/archive.php?view=1&day=28&month=12&year=2022