Mike. I think you are about 120 miles from the Tx and I am about 20 miles so based on the inverse square law only, your signal will be about 16dB less than mine, but its worse than that because of excess ground wave attenuation over an average earth plane which taking a stab using the formulas I have will be about another 10 dB making 26 dB difference. Putting that back into the power calcs makes a staggering 1.6MW required at Orfordness on the Omni aerial to get 'suffiolk' type coverage in camberley. Actually 648 when the world service of the BBC had it was over 2MW towards the continent, but very little off the back of the array such that on some bearings it was barely audible at 20 miles, Such was the very high front to back ratio of the aerial. All the best