In message , Bill Wright
writes
Don't you have to see the whole thing as a system, with a length of
unscreened wire that had sparks at both ends?
You'll no doubt remember that spark transmitters were banned because of
the interference they caused. So whilst there will be a little r.f.
From the cables the sparks at both ends were the real culprits, but
plugs are totally enclosed by metal to ground, so it had to be the spark
between the rotor arm and the adjacent plug lead terminal in the cap,
which has no Faraday cage of any sort around it.
--
Clive