I am having difficulty with a wideband antenna receiving any signal strength from Sudbury on ch 68. I am Using an Alba freeview box which reports a moderate strength on ch 48, poor on ch 56, but none on 68. According to http://www.dtg.org.uk/retailer/tx_ea.html the power of the Sudbury transmitter(s) on each channel is 5.0 kW, 1.1 kW and 8.1 kW respectively. If ch 68 is so much stronger, even if my antenna has a bit of gain droop at the top end, why do I register absolutely nothing? Is there a strong directional component so that there is no signal here in CO4 0JX, Colchester North? Is there a web site which can provide polar diagrams of signal strength?