[timgr]

Thanks for the interesting and detailed response.

Looking at this a little more, I notice that the roof has an abandoned bathroom vent next to the chimney. I could take that over as my wire entry point (the alternative is to drop wires over the side of the house and go through the shingles and sheathing into the basement stairwell, where the small low window is). The mast ground could then follow the stack chase down to the basement floor, around the perimeter of the basement, and close to the current water pipe service ground attachment. See any issues with this?

The coax could also follow the stack to the basement, but there it must leave the stack. Whatever I end up with, the coax must diverge from the mast ground quite a ways from where the mast ground would be bonded to the service ground.

Now, your post #20 says to install a ground block and "connect it to the electrical service ground at the same point you connected the mast ground." That could be interpreted as sending the ground block wire back to the water pipe where the service ground is. I don't see any need for using a parallel conductor to the mast ground, as long as the coax ground ties into the mast ground before they diverge.

You also advocate "reasonable steps to encourage fault current to stay outside my house" - so you would take the mast ground around the perimeter of the house to the point of entry with the shortest path to the service ground? Doing that, the ground block would be way far away from the service ground... so put the ground block where they diverge, up by the mast?