I didn't carefully read the whole thing, too long. But some observations:
A crank up tower is very hard to ground as there is no good connection
between the tower sections so your cables are prone to carrying a great
portion of the strike energy if the tower is hit.
I didn't see where you described the ground system at the shack that the
single point ground is connected to. It needs to be extensive, many ground
rods and radials and a very short connection with 6" or wider copper strap
to the bulkhead panel (the single point of the ground system).
I notice that you said that you run a ground wire, that is rather long, over
to the power and phone line entrance.
For maximum protection you should run your power (by a cable within the
house is fine) over to the single point ground bulkhead and place power line
protection devices directly on the bulkhead panel. Feed all equipment ONLY
from that power source.
Do the same with the phone lines to the panel.
Now you will have a "true" single point ground system that will hold all
equipment to the same potential.
The trick to a good single point ground system is zero length between all
leads feeding your equipment from outside sources. Also a very short,
extensive ground at the single point.
73
Gary K4FMX
> -----Original Message-----
> From: towertalk-bounces@contesting.com [mailto:towertalk-
> bounces@contesting.com] On Behalf Of Dick Green WC1M
> Sent: Friday, May 30, 2008 2:33 AM
> To: 'Roger (K8RI)'; 'Skip K3CC'
> Cc: towertalk@contesting.com
> Subject: [TowerTalk] my long lightning story (was RE: lightning strike)
>
> For 10 years I thought I could protect my station from anything but a
> superstrike, but that was before I put up a 110' tower, and before the
> summer thunderstorms around here became more violent (Climate change? Who
> knows?)
>
> Previously, all I had was my 72' tubular crankup, almost always retracted
> to
> 22', a 75' AB-577, two 48' AB-577s, and several wires antennas strung in
> trees at the 65'-75' level. All the "towers" are either below the level of
> nearby trees or close to it, and all are at least 30' below the tops of
> trees on the high points of our land. The crankup has an extensive ground
> system, 12 ground rods spaced 12' apart, Cadwelded to four radials of 1/0
> wire attached to the base mounting bolts. There's a utility cabinet next
> to
> the tower with Polyphaser coaxial suppressors for every antenna and
> Polyphaser rotor suppressors for all control cables. All wires run to the
> shack through 265' conduits buried 4' deep, and there's a length of 1/0 in
> the bottom of the trench for the entire length. At the shack end, there's
> an
> identical utility cabinet with an identical set of suppressors. The panel
> in
> the cabinet is attached to a single point ground. The long buried piece of
> 1/0 is also attached to the SPG. There's a copper bus bar running along
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|