Very well said. There is an excellent discussion of grounding fundamentals
in the ARRL Antenna Book. In the 17th edition (1994), pages 1-10 through
1-16 cover the section titled "Lightning and EMO Protection." Figure 16 on
page 1-12 is a drawing showing interconnection of tower, telephone and AC
power grounds.
I too have followed this advice, but have also included bulkhead arrestors
for all coax lines and control cables, and a disconnect box in the shack
that grounds the center conductor of all coax lines when the power is turned
off. My single tower is only 150 feet tall, but has been struck repeatedly
(four observed direct hits). The last strike was so big it destroyed the
rotor and blew to pieces the 144/440 base station antenna on top of the
mast. Nothing inside the shack was harmed.
Keith
-----Original Message-----
From: towertalk-bounces@contesting.com
[mailto:towertalk-bounces@contesting.com] On Behalf Of Tom Rauch
Sent: Wednesday, July 21, 2004 7:33 PM
To: Eric Rosenberg; rfi@contesting.com; towertalk@contesting.com;
pvrc@mailman.qth.net
Subject: [TowerTalk] Re: [RFI] Question re: Whole House Surge Protection
> My neighborhood was zapped on July 4th. An indirect hit
caused a
> powerline surge at our house that nailed my Omni-6+ and
other devices
> (wireless phone, answering machine, home alarm control
panel, computer).
> Oddly, while our hit came trhough the AC line, my
neighbor was hit
> through his cable connection (our TVs were not hit).
Hi Eric,
The first thing I'd do is review the proper way to ground your utilities and
radio feedlines. I'd be willing to bet neither you nor your neighbor have
good single point grounds for all wiring entering the buildings, and do not
use single point hubs at TV sets and the like.
Every feedline entering the dwelling should be through a grounding block
that has a very low impedance to the telco, CATV, and power line grounds.
When that isn't done, lightning loops through the building and wipes out all
sorts or equipment in weird ways, and a lightning protector almost certainly
won't do a thing.
I have a 318 ft tower that gets hit several times a year, I have smaller 200
ft and 160 ft towers, and miles and miles of antennas and cables that remain
connected 24/7 every day of the year. In spring I took a super bolt that
actually melted feed cables, the telephone lines, and burned about 2"
off the top of a two meter 4 bay dipole at the top of the
318 ft tower.
I don't have a single polyphaser or anything else, although every "group" of
electronic devices has a common point "ground" where all cables enter and
leave, and before any cables come into the house they go through bulkhead
feedthroughs that are common to the utility company grounds.
I never lost a modem, never lost a TV set, and never lost anything in my
shack except a single 2N3904 transistor that switches relays in my
Beverages. Everything was plugged in, everything was connected to the
antennas.
While I not saying surge protection should be ignored, how you connect
things provides nearly all of the energy diversion. If you don't follow
proper lead routing and grounding, there isn't a suppressor in the world
that will protect your gear.
73 Tom
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|