Crackle wrote:... neither 909 or 1215 are transmitting Gold ...
I didn't say they were, Mike!
I thought we were discussing propagation conditions here, not programme content!
I chose Brookmans Park because it is very close to Saffron Green, so its signals share the same path to you. There is a complication, though, because both Brookmans Park transmitters form part of a synchronised network - 11 transmitters on 909kHz and 14 on 1215kHz - although I think we can discount the one in the Dartford Tunnel!
However, you can't synchronise sky waves! The path length of a sky wave is continually changing, resulting in a varying phase difference between it and the stable ground wave* which causes fading when one cancels the other. If you were having problems caused by sky waves, the multiple transmitters on both those frequencies would surely have created complete chaos?
* Reception of Radio Luxembourg was surprisingly more stable in Western Scotland and Ireland (from personal experience) than in London and the Home Counties because they were beyond the reach of the ground wave and solely at the mercy of sky wave propagation!
Here we got both, with predictable results.