"Robert11" wrote in message
...
Hello:

Very interesting comments on my question of a few days ago re lightning
arrestors.
Thank you all for trying to educate me on this subject; really find it
confusing.
Thread is a bit buried by now, so thought I'd start another one.

I fully understand that the best approach is to (also) just disconnect
everything.

But if not around, here's what I don't understand and concerns me.

Assuming a "nearby" strike, and a subsequent emp pulse that's picked up by
a receive only antenna
wire strung outside:

No matter how quickly an arrestor's gas tube fires, and diverts the pulse
to a good RF ground, the fact that it takes
a few hundred volt threshold to fire makes "any" gas tube type of arrestor
almost worthless re the protection of a receiver whose front end certainly
won't take a few hundred volts, even for u-seconds, probably.

Do you agree with this statement, or am I missing something ?

Thanks,
Bob


Hi Bob,
I'm Ace - WH2T.
Here's my story.
So far I have been very lucky. Neighbors closest on my north and south sides
have both been hit, BAD SEVERE strikes. We live on a hill.
I had a strike take out a cheap portable TV that was in the kitchen and it
blew a fuse in a VCR. It also came in the telephone line and blew up some FM
intercoms that were connected to the telephone line. After that happened I
had a commercial lightning arrestor installed by my electric power company
at the electric meter.

I use 2 HF antennas, a 272 ft delta loop and a 160 meter band 1/4 wave
inverted L antenna, both antennas go thru my MFJ-989C Tuner . When I am not
on the air I leave the antenna switch on the tuner in the "Dummy Load"
position. That connects a 300 watt 50 ohm resistor to the radio's antenna
jack and grounds both antennas.

The main lightning problems I have had in the 12 years at this QTH are
surges coming in the telephone line.
I noticed when I moved here that all the telephone jacks in the house were
black. I lost 9 computer modems in short order. I installed the smallest
fast blow fuses I could find in both sides of the telephone line (they are
under 100 ma) . The next time there was a nearby strike it blew both fuses
and still blew my computer modem.
After that I installed three 130 Volt MOVs outside the house in the
telephone box , one across the telephone line and one from each side of the
telephone line to ground. I also installed a very small pigtail neon lamp
between or across the 2 sides of the telephone line. It acts as a gas tube
type of arrestor, and lights when the telephone rings, or when lightning
strikes nearby; the threshold to fire is under 100 volts. I also installed a
DPDT knife switch , to break the telephone line when the computer is not
connected to the internet. No further problems. I live out in the country
dial up is all that is available here other than expensive satellite access.
Anyway , now on to your question.

I got the following Info from another ham.

From my commercial broadcast days the lightning control solution for
tall insulated base AM towers (which were always experiencing direct
lightning strikes) was to use 2 inch diameter copper balls spaced 1/4
to 1/2 inch from each other (depending on peak RF voltage present) at
the base of each tower on heavy arms as a lightning spark gap. Then
the 1/4 inch tubing feeding station RF into each tower base would be
formed into a 3 turn loop with a 12 inch diameter, with about 2 inch
spacing between each turn. I would do the same with the coax feeding
repeaters and studio-transmitter links on these towers. I never lost
any equipment using these techniques.



I realized I have to mention that I use an inductive RF coupling-
impedance transformer in my homemade transmatch in order to eliminate
a direct dc path from the ladder line to the transceiver input. I
also use high tension teflon coated wire for the primary turns in the
transformer. Lightning would be common mode on the transmission line
and therefore not inductively coupled through the transmatch. The
issue then becomes voltage breakdown between transformer primary and
secondary windings (along with minor capacitive coupling), hence the
teflon coated wire.

Concerning possible lightning on the ladder line, I use adjustable
spark gaps from each conductor to ground outside of my building.



I hope this is of some help.

Ace - www.WH2T.com