(Warning: Loud) What is this sound in the MW band? (raw.githubusercontent.com)

submitted 8 months ago* (last edited 8 months ago) by [email protected] to c/[email protected]

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Heard this sound at about 1200 kHz AM using an analog consumer radio in eastern Czech Republic. (Could be a superheterodyne mirror from another band, though.) What is this? I don't have an SDR or other ham equipment, this is just a mic recording.

I thought it could be useful to drive mice out of a garden shack but it was gone the next day.

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[-] [email protected] 3 points 8 months ago

My guess is a cap gone wild in some tank circuit, hence the timed sounds (cap charge/discharge cycle).

[-] [email protected] 3 points 8 months ago* (last edited 8 months ago)

Probably not, tank circuit (aka LC resonant circuit) capacitors are low capacity and charged/discharged at the carrier frequency, not every second. And those are pretty reliable kinds of capacitors (polypropylene, usually).

Are you suggesting my receiver is defective? I think it isn't, I was able to pick up a Hungarian MW station (otherwise AM has been shut down in Central Europe).

The audible sweeps seem to be purposefully coordinated, each is shifted by a constant amount. And why would anyone be broadcasting a 5300 Hz beep? (Or a pure sine wave at two frequencies separated by 5300 Hz, which AM receivers would interpret as this beep.)

this post was submitted on 16 Nov 2023

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