RED SANDS
My friend Stephen Muirfeld was engineer on Radio 390 in late 1966, just after he left Radio 270. I have seen a picture of him on there with both the RCA 10KW transmitter, AND the FM transmitter they bought from the Cheeta II. They didn't have a suitable aerial for it though.

A phenomenon called tropospheric ducting is responsible for giving long range FM DX where high pressure intervenes in the signal path. Its more prevalent at lower VHF frequencies - years ago summer days were bad for TV reception as the high pressure areas DUCTED distant TV signals, especially on the lower BBC channels (around 50 - 60 MHz). This was less noticeable at the Band III (ITV, Channels 7-12), but it was common on the FM band. IOt still is - summers day and you can often hear stuff from Switzerland, Spain and all over in between local transmissions.

Maybe not enough people DXs around these days so no-one notices it any more? I never heard RNI on FM myself (too poor for a VHF radio!) but know several around the Yorkshire Riviera who did. Surprised that Mike Ross, who claimed to be an engineer was so sceptical.