My T-mobile reception at home fluctuates from full to weak even though according to the mast finder on the OFCOM website the mast is only a couple of roads away. But there's a main railway line running through the village and yesterday while I was texting I noticed that the fluctuation seemed to correspond with an intercity going past, getting better as the train went out of earshot. Is it possible that all the extra phones on the train weaken the signal as the train goes through? (The mast only serves the village because it's in a valley.)