A what? A "special spark gap isolation capacitor" sounds fishy to me. A
spark gap might be used in a lightning arrestor to discharge to ground, but
these antenna isolation caps are not spark gaps, they are high voltage
ceramics, aren't they? Why would you want to isolate the signal line only
to have it discharge over a certain voltage into the tuner? Can you even
build a spark gap that will have the ability to pass significant RF like a
cap? Is this some type of capacitor that is designed to fail as an open
circuit instead of a short, maybe? Maybe they are just old style single
layer ceramics for this reason? I'm not sure, but I'd love to see some
description of this design so we could learn something.
Certainly there is a potential for compromising the safety of the system by
using inferior parts or wiring it incorrectly, and I agree that these
isolation blocks can be had cheaply enough that it is not worth the trouble
to find replacement parts and repair them, but lets not misinform in the
name of safety. Most of us come here to share information and learn, not to
be baffled by bullshit.
Leonard Caillouet