Grant_k...Thanks for the kind remarks.

Actually intermodulation taking place practically anywhere would not surprise me too much, one of my ex bosses some years ago studied a case where it turned out that the galvanised fence wires around the station were the cause. Transmitters as used these days are probably a little different since I gather they tend to use a linear amplifier with the low level stuff fed into it. So long as the multiple carriers fed in are not to high then there should be little intermodulation. I once wrote a BASIC program to work that out for a satellite station. The old class C output stages were highly non linear and would happily mix whatever was going through with anything coming in the output, and of course the output filters were often quite limited. But yes, a receiver being a low level amplifier makes it quite easy to drive it into nonlinearity. I dopn't know anything about this particular case that is not public knowledge, but will agree it is perfectly feasable that the Vodafone signals could be intermodulating with Telecom signals in the Telecom amplifiers, especially in a co-location case. It may also be that more than one thing is happening, from what I see above VF are tweaking their masthead amps a bit in some places.

just to take you back a few years, I know of a case in the VHF band a few years back where it took some time to figure out the problem. A very weak signal was just opening the gate (squelch) on a receiver. None of the combinations of transmitters in the district could be implicated, eg the 2A -B products and so on were worked out for everything within miles...didn't seem to implicate anything. Finally it was realised that the local oscillator from a receiver about 25 miles away, together with a local transmitter, could produce that frequency. The receiver was turned off and "La voila", the problem was fixed. Those receivers had an RF stage, so the local oscillator should have been at a low level, but nevertheless was radiating out, and combining with the transmitter somewhere. I think the particular receiver was a valve one, so should have had excellent isolation, but there were quite a few transistor ones around by then so I'm not sure. The early transistor sets were of course not wonderful from an intermodulation or signal isolation point of view, that was before MOSFETs, gallium arsenide, or any of that wonderful stuff. Valves were quite good of course, apart from being mechanically fragile, power hungry, and inclined to lose emission. And of course extremely bulky by modern standards. Guitar players still seem to love them but I find it hard to see why.