Robert 11 wrote:
"For either unit is the arrester placed between the Balun and the
antenna, or between the Balun and the radio? Why?

It likely is superflous.

Coax connectors make lightning arrestors of sorts. They clamp voltage to
the arc sustaining voltage (less than 100 volts), once they fire. If you
are transmitting, r-f may keep the arc alive. Broadcast transmitters
sense the arc and shut the transmitter down for an instant to quench the
arc. Communications radios usually don`t bother as their transmissions
are sporadic and usuallly short.

Remember, coax shield is impenetrable to r-f. D-C conducts right
through. R-F does not due to skin effect.

In countless VHF antenna installations atop tall towers around rhe world
we never used a Polyphaser or similar arrestor on the coax, yet never
had damage to radio antenna circuits, even to transistorized radios.

We always used folded driven antenna elements. We grounded the coax at
the top and bottom of the antenna tower. The tower due to its size has
lower surge impedance and carries the bulk of the lightning current to
ground. The tower is well grounded.

We found it necessary to use brute-force pi-filters on every power wire
feeding the radio including the neutral wire. We used tower lighting
chokes in the pi-filters to cary the current required to power the
radios. We shunted the filter inputs and outputs to ground with MOV`s
(across the a-c capacitors).This limited surge voltage on the radio and
on the powerline. It eliminated all damage to the power supplies in the
radios. These filters were found necessary only when transistor radios
were introduced. Before that, the grounded antenna system sufficed for
tube-type radios.

Best regards, Richard Harrison, KB5WZI

Peak current of 100,000 A for 1 microsecond in wire with resistance of
(say) one ohm gives energy of 10,000 Joule.

If the wire is No. 12, that would warm it up pretty well, but vaporize?

Where have I gone astray?

TIA

Chuck

chuck wrote:

Peak current of 100,000 A for 1 microsecond in wire with resistance of
(say) one ohm gives energy of 10,000 Joule.

If the wire is No. 12, that would warm it up pretty well, but vaporize?

Where have I gone astray?

TIA

Chuck

So far, correct. But, that 10,000 J equates to 1E16
[100,000,000,000,000,000] watts peak power.

There is a thermal shock wave that occurs in the wire. There is a
transient magnetic wave in the wire.

The failure mechanism has been empirically correlated to peak power
times [pulse width^1/2].

The wire, or portions of it goes away!!