Dave, through his posts on the topic, brings wisdom to the discussion of lightning protection. There is literally no end to the measures one can employ in this regard and which, for the hobbyist, could be unrealistic.
The first thing to keep in mind about lightning protection is what you are protecting. You have to protect people and then property. One way to do this is to design and install your system so the lightning is kept out of buildings. This requires, at minimum, devices or methods of providing a path to ground for lightning for all conductors at the point of entry to the building as detailed in the National Electrical Code (NEC) and local ordinances. It is also required that masts, towers, poles, or other metal mounting be grounded.
If you can protect your outdoor equipment then so much the better but this is secondary to protecting people and buildings and is probably not going to save the equipment from a direct or nearby strike. If a choke is installed in the ground lead at the base of the elevated transmitter the problem is that the power and audio feed wires are now "floating" and can conduct the lightning into the building (as well as to act as radiating conductors which defeats the intent of using the choke). It will be very important that the protection on these lines where they enter the building be up to the task. They should have this protection even if the transmitter is grounded without the choke.
Neil
So I guess if you did a roof mount you would ground the antenna (example grounding lug on hamilton rangemaster)straight to earth. Does the roof need to be grounded to earth.
Respectfully
Mike
Mike,
I would primarily because I cannot think of a reason not to.
Oblige me a story about this sort of thing. While I lived with my parents as a teen I was the "roof" man since I had no fear of height and had made extra money installing and fixing TV antennas so it appeared that I knew what I was doing. When their antenna needed replacement, I climbed onto the metal roof on the back porch so I could reach the antenna which was mounted on a mast attached to the fascia at the peak of top roof. All was going well until I disconnected the ground lead from the mask and received a pretty good shock. It turns out that when the roof was installed a nail was driven into a wire which made the roof "hot". For years we didn't know this since the ground wire was routed over the edge of the metal roof and grounding it.
It also turns out that their electricity bill went down quite a bit when I found the circuit and cut it.
Your roof could well be OK but one never knows.
Neil
Thanks Neil I sincerely appreciate you time and being able to benefit from your experience as the roof man. At my age, I don't think I could bounce back as fast as a teenager. I appreciate the amount of knowledge I gain from this site. I bet there are some great war stories out there.
Respectfully,
Mike