On Sunday, March 8, 2015 at 8:22:14 AM UTC-4, Leon Fisk wrote in rec.crafts.metalworking:
On Fri, 6 Mar 2015 13:31:22 -0500
"Jim Wilkins" wrote:

I bought a single-pole relay rated for "only" 75KV once. It was the
size of a desk lamp and opened the contacts several inches.

Ouch!

The way I remember it the product used standard relays. The key
was that in the off/relaxed position everything was shunted
together to common ground point. Lightning could still jump
the relay but it would be greatly reduced with everything
shunted/grounded together. It was a pretty ambitious scheme if
I remember correctly. The antenna lines were all disconnected,
shunted too. Depending on the frequency, antenna switches can be
pretty expensive too...

One of the radios I used to work on was the Motorola Micor series.
They
had an interesting antenna relay in them. They used two magnetic
reed-switches encased in an aluminum (I think it was
aluminum) housing.
One switch had a magnet shrink wrapped to it keeping it in
the closed position (receive side). A small coil (12vdc) went
around the metal
case. To transmit they applied 12vdc to the coil which in
turn closed
the open reed and opened the one with the magnet affixed...
For an overall image:

http://i.ebayimg.com/00/s/MTA0N1gxMzg5/z/li4AAOSwEeFU4uN5/$_1.JPG

They made a great lightning arrester. Many, many times that is
the only part I would have to replace after a tower lightning
strike. If you
took one apart, quite often the two reed-switches would
be completely obliterated, just blown to bits... Motorola had
a lifetime guarantee on those relays. Sent many of them back in
for warranty replacement. You
couldn't tell what happened to them without taking them apart


Leon Fisk





8:22 AM (2 hours ago)















On Sat, 07 Mar 2015 22:55:42 -0500
John wrote:

snip

If the tower was not properly grounded lightning will cause damage.
Good grounding will carry off the charge and prevent it from doing
damage. Our towers would get hit almost every lightning storm and no
damage to the electronics. Most all of the telecommunications towers
can withstand a direct hit with no damage. The power has to have some
place to go and the best place is directly into the ground with the
proper grounding system.


Psst... John, wake up, you're dreaming...

I worked in two-way radio communication most of my career. Several of
the towers I serviced equipment at were grounded to R56 spec, which was
very ambitious and the best at the time. The equipment still took hits
that caused considerable damage...

And other towers that had little to no grounding and got hit regularly,
had very little equipment damage. Go figure...

Maybe our lightning had more oomph than your lightning ;-)
Psst... John, wake up, you're dreaming...

I worked in two-way radio communication most of my career. Several of
the towers I serviced equipment at were grounded to R56 spec, which was
very ambitious and the best at the time. The equipment still took hits
that caused considerable damage...

And other towers that had little to no grounding and got hit regularly,
had very little equipment damage. Go figure...

Maybe our lightning had more oomph than your lightning ;-)