Thanks to you both for prompt and detailed responses. We rarely get thunderstorms here, but no sooner had I disconnected the combo surge protector and ground block, and large thunderheads started piling up in the East and moving West.
GUM: The mast is grounded, but I'll need to swap in a new shield ground block to replace the existing combo shield block/surge protector (they're fused together).
westom: from the product description: "Device uses gas tube overvoltage technology to shunt surges to ground, when device is properly installed." So there's nothing much different from this and the way an ordinary shield block will behave? (lol, except maybe $10). I hadn't noticed any significant attenuation on unamplified signals prior to this, but that's just ad hoc observation, not instrumentation. The fact it won't pass power in the reverse direction makes it useless for my current build, though. Is this the kind of Polyphaser device you're thinking of (
http://www.theantennafarm.com/catalo...oducts_id=1933)?
However, if that's just an inline piece with no ground, what's to stop all the energy from arcing the gap? Or is it simply enough resistance to persuade the energy to take the mast/shield ground route?
thanks again.