How long did it take them to notice

Ahhh, back in business!
It's over 40 years ago, but if my memory serves me well, some weeks, maybe 3 to 4 - I've always suspected the BBC sussed it out and let the authorities know, all that held them up was that they couldn't believe it was coming from a BBC building! The transmitter wasn't actually mine, it was ex-military and came from one of the surplus shops, that were in profusion at the time, for £3.50 - some guys we knew tweeked the frequency.

The tape recorder was more serious, it was a Ferrograph - all I could afford afterwards was a cheapo reel to reel from a high street shop.

Most people doing this at the time were campaigning for more variety in broadcasting, we only had 3 BBC stations, we were operating at a tangent, we were under the impression that the populus needed four hours of blues every evening - they weren't ready for it!

I suppose we were the 60's equivalent of hackers - getting caught smoking pot and getting girls pregnant were about the only other two things we feared!