Re: Strange VLF signals


D R
 
Edited

Hi Allan,

Interesting that your 16kHz group didn't appear until well after sunrise this morning.  Which direction are the nearest panels facing?

I didn't do a sunrise recording today as the forecast was for a thick misty start, which it was, so the light levels wouldn't have matched the sunrise time anyway.  However, it was a cloudless late afternoon and evening so I did one for sunset and got a couple of perfect matches: the 50Hz intermediate carriers I noted yesterday went off at 16:56:32, coinciding with the actual sunset time, and the 16kHz and 100Hz carriers all went off at 17:17:52, which was just before last light.  I also did some RF sniffing inside the house with a laptop and dipole this afternoon and found, as expected, that the wiring is carrying the 16kHz group - but far worse noise was coming from all the central heating radiators.  When the dipole was held near any one of them the laptop screen filled from side to side with 100Hz carriers, indicating that it's the mains earth that's carrying the noise.  (Or are the radiators just reflecting the noise?  If they are, then they are also amplifying it as well.)  Moreover, I tested again after the 16Hz group had gone off, and all the RF from the wiring and radiators had gone too.  Conclusive proof that it's solar panel inverter noise?  I think so.

The wide band of strong noise centred on 101.3kHz is most probably the eLORAN signal from Anthorn, near Carlisle.  I receive this as a 30kHz wall of digital hash from 86 - 116kHz, and it sounds like the rapid popping you heard.  It covers a lot of spectrum, but I did happen to catch it a few months ago just at the instant the transmitter was turned off for maintenance - and there's absolutely nothing hidden underneath it!

Regards,
Dave

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