>> I have 3 towers up, one at 80', one at 50' and one at 70'.
> Each is a Universal Aluminum self supporting tower which I
> have supplemented with a single set of 3/16" steel guy wires
> about 2/3 of the way up. Each tower leg has it's own 10'
> ground rod connected with a 3' length of #0 wire. >>
>
> Unfortunately you have almost no ground at all on the
> towers.
<big snip>
My grounding is similar to Tom's on a smaller scale. I only have two
towers; the big system, and a little 32 footer. Between the two I have 32
or 33 (lost count) ground rods cad welded to over 600 feet of bare #2
copper. I'm using polyphasers on the coax coming into the bulkhead, but I
don't have any MOVs installed. The ground systems for the two towers are
not connected as the shop and the house are on different electrical feeds.
I do need to add a larger common between the bulkhead and the electrical
entrance and I like the idea of the soft copper all the way around the
house.
Although I do use Polyphasers I take their information with a grain of salt.
Remember, Polyphasers like MOVs wear out, or blow out with use. A direct
hit to a bulkhead full of them can get really expensive. MOVs are cheap but
you do need to get the correct ratings. When purchasing MOVs remember your
line voltage Peak to Peak is 1.404 times the RMS and the MOV needs to be a
bit above the P to P. If you have line voltage a bit high at 127 which does
happen, that's a peak to peak of just over 178 volts. Put in an MOV rated
under that and it'll get fried, right away.
That said, "Sparky" seems to like me and has an affinity for my location as
the big tower gets hit about 3 times a year on average although it's already
been hit twice this year. Since going to the big system, I've only lost one
Polyphaser which happened to have been on a grounded line (both sides) and a
computer. I later discovered that 110VAC line to that computer had a poor
connection for the neutral back at the entrance panel. Prior to that, when
I had a smaller tower and much smaller ground system, I did get one piece
of 7/8" Heliax blown out and lost the front end of a 2-meter rig. The
station configuration varies a bit from day to day, but there are three low
band stations, three UHF/VHF stations (four if you count the Yaesu 897d in
the shop), and two computers which are usually interfaced to the HF as well
as the VHF/UHF (sometimes packet) stations. Rarely is anything disconnected
and the computers run 24 X 7 except for periodic maintenance.
Some consider that a lot, but considering the amount of *stuff* have
connected (and that loose neutral) and the number of strikes my system
takes; I think it's darn little. Normally about the only thing that happens
even with a direct hit is the network resets.
That network is a gigabit running on CAT-5e with the run to the shop going
within 10 feet of the tower base. It a 132' run between computers hooked to
different electrical feeds. Between 4 computers I have a total of 2.62
terabytes of storage (Just took inventory). All but 300 Gig on this one is
remote. Out of all of that I have less than 200 Gig free. The data is
backed up to DVDs, but keeping all that up-to-date is nearly a full time job
in itself which is causing me to switch about half the storage to external
USB-2 drives. The internal is going to SATA RAIDs.
So, between the ham station and computers a good ground is essential.
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
_______________________________________________
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.
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