Hi Brad,
There was a presentation by Mike Scott, and discussion on "Earthing", at the ADS-B Sydney Message Board workshop day last November (organised by Kurt).
I am not a qualified electrician either, however a couple of points you might like to follow up on are :-
- I think the Australian regulations require your earth cable to connect to the House Ground via some type of device (forget what it was called).
- From the images it is hard to tell where the earth cable goes. It looks to be connected to the Mast, but I think it also needs to be connected to the earth of the ADS-B Antenna cable.
Maybe Kurt can help with Mike Scott's presentation (even thought the regulations are different overseas), and Phil Henry or Scott Pepper could help out.