I'm beginning to suspect that there is something mixed up in how this set was installed. If Bucky can get loads of channels in the rolling hills of Wisconsin, surely I should be able to get the same here. It's only rolling hills between our place and Seattle. If the antenna was pointed due east that would be another problem as there is a mountain range in the way.
I'll get Mr. Bean to climb to the roof with the voltage meter this weekend. Hopefully that will shed some more light on this problem.