Original poster: Ed Phillips <evp@xxxxxxxxxxx>
Dennis,
I was running my coil in the garage and was getting a few strikes to the
ceiling. Evidently it entered a wire and went inside the house and traveling
many feet burned a 12 gauge insulated wire in two at a wall socket. Also
fried the answering machine hooked to the socket with an AC to DC wall
transformer.
Brad McPeak"
Very small correction. It wasn't the current from the strike
itself which burned the wire, but the line current supplied when
the wire arced over at that point. Lot more current and melting
power than in the streamer. This was apparently a very common
problem in the days when hams used high-power spark transmitters
(most guys ran at least a kilowatt line power) and they reported
all kinds of such problems which were called "kick back". One of
the commonest ones for some reason was melting down of light
sockets. The stories report molten brass dripping out of the
socket and onto the floor, but I suspect that's a bit of an
exaggeration. One of the partial fixes was known as "kick back
preventer" and put capacitors across the power lines. In the case
of the ham problems there weren't streamers striking the lines but
there was inductive and capacitive coupling from the antennas,
which tended to be quite large. Turns out that the peak powers
transmitted were in the megawatts, as with TC's. A typical "high
power" station used an 0.01 mfd storage capacitor charged to 25 kV
and discharged through a synchronous rotary gap. At the operating
frequency of 1500 kHz the primary tuning coil was a single turn of
heavy copper strap or bar, less than a foot in diameter, and
inductively coupled to the antenna loading coil. The resulting
antenna current was of the order of 7 to 10 amps, as read with a
thermocouple or hot-wire ammeter.
Ed