On Nov 30, 11:05 am, Michael Coslo wrote:
wrote:


There is a whole lot of misinformation regarding grounding.

Understatement of the day . . .

An
interesting mental exercise is taking a tower say 50 feet from your
house. According to some, in order to comply with NEC, the tower has to
be grounded by sending a lead back to the house to that single ground
point. I guess they want to insulate the tower base from ground - no
ufer's here, thanks. Sounds like a disaster waiting to happen.

Of course.

Over the years I've dealt with a grand total of two lightning
"events". I had a 70' 45G tower with a monster mast which was topped
by a homebrewed clone of a 2M Ringo Ranger which went to 90+ feet.
Lightning magnet. There was one ground rod alongside the concrete base
which was bonded (clamped and silver soldered) to the tower by a 1/8"
x 1/2" copper strap.

There were three runs of coax, a run of shielded rotator cable and an
unshielded run of 14/3 Romex up the tower with all shields and the
Romex ground bonded to the tower. All the radio gear in the basement
shack was grounded to the water line which was ~25' from the radios.
Not slick by today's standards.

Along came the first hit and my whole world turned "bright electric
blue". Power line/brown underwear hit. The thunder was still rumbling
loudly so I scrambled behind the gear and furiously got into yanking
plugs out of outlets when *bang* another hit . .

In the end there was all kinds of damage to the house wiring, TV sets
and kitchen appliances toasted, second floor wall outlets atomized,
etc. The only damage in the "radio room" was to the two vaporized disc
ceramic AC line bypass caps in the 75A4.

From this experience I learned that (a) lightning certainly can strike
the same place twice in rapid succession and that (b) lightning can
choose to hit power lines which are 30-40 feet *below* mongo grounded
objects like a towers which makes no sense at all and (c) there are no
manmade "cures" for lightning. Except maybe paid-up insurance coverage
and prayer . .

The good folks at Polyphaser have some excellent Technical notes. Kept
me busy a long time reading the stuff:

http://www.polyphaser.com/technical_notes.aspx

Of particular interest is Ham Radio Station Protection:

http://tinyurl.com/2aymw9 (tinyurl needed - its a long one)


That's a really good one. I'll print it out and dig into it. Tank yew
Michael.


It is largely about lightning protection, but has good stuff pertaining
to grounding.

- 73 d eMike N3LI -

w3rv