Depends on how much money you want to spend. Polyphaser sells a really nice
line of copper bulkheads that would meet your requirements exactly. They
have provision for grounding the cable shields and terminating each line at
a lightning arrestor. I'm pretty sure the arrestors can be mounted on the
shack side of the bulkhead, so the equipment lines can be disconnected from
inside. Of course, the bulkhead is set up to be connected to your
single-point ground outside the shack.
However, these bulkheads cost several hundred dollars and up. You might be
able to fabricate your own, though. I would get a copy of the Polyphaser
catalog and take a look at the pictures and drawings.
As for getting the cables to the bulkhead, I would recommend that you bring
them up the exterior wall of the house in some PVC electrical conduit, then
terminate the conduit in the bottom of some sort of metal or plastic utility
box. You can then cut a hole in the back of the utility box that goes into
the house. The cables come up from the conduit into the box and enter the
bulkhead (and house) through the back of the box. The bulkhead sits between
a pair of wall studs. You can get or fabricate a utility box with a lock for
cable and house security. Without the box, you would have to use a 90-degree
section of PVC, which can be hard to pull cables through. Also, the boxes
give you the ability to access the cables and back of the bulkhead much more
easily.
I didn't use a bulkhead. I terminated the PVC in a heavy-duty waterproof
metal utility box. The cables come up through the PVC into the bottom of the
box. There's a metal grounding panel in the back of the box (it was an extra
option), on which I've mounted the lightning arrestors for coax, rotors,
etc. The cables connect to the arrestors, then short cables go from the
arrestors through a PVC-lined hole in the back of the box into the house,
then up through another pair of PVC-lined holes through the floor of the
shack.
I leave the cables connected all the time. If there's a thunderstorm in the
area, I try to disconnect the cables right at the equipment because it's
easier to do it there (well, that's true of the coax and rotor cables; there
are three control cables that I don't normally disconnect -- gotta get some
Cinch-Jones plugs for those guys!) If a really big storm is coming, or if I
leave the house for a few days during thunderstorm season, I can disconnect
everything inside the utility box, but that requires a screwdriver at the
moment (need more Cinch-Jones plugs!) Regardless, the cables always remain
connected to an identical set of lightning arrestors in an identical metal
utility box on a pedestal at the base of the tower (per ARRL and Polyphaser
recommendations.)
I also lower the crank-up to 22', well below the trees, whenever
thunderstorms are in the area.
I have an extensive ground system at the base of the tower -- 11 8' 5/8"
ground rods in a star pattern connected with 1/0 stranded copper wire, all
of which is connected to a radial field for a four-square consisting of 240
35' long radials. The whole shooting match is connected to a single-point
ground outside the shack through 250' of 1/0 cable buried at the bottom of a
four-foot deep conduit trench -- essentially a huge horizontal ground rod.
All ground connections are Cadwelded.
I'm sure it's not perfect, but it gives me peace when either I forget or get
too lazy to disconnect the cables. With that ground system and double surge
protectors on every wire coming into the shack, I haven't had a glitch yet
(fingers crossed.) We did have a storm last summer that was close enough to
induce a surge on the data line coming from my annemometer to the weather
panel in the shack. At the time, that was the only unprotected line. The
panel would beep whenever there was a lightning stroke. No other equipment
in the shack showed any reaction to the surges.
73, Dick, WC1M
-----Original Message-----
From: Dave D'Epagnier <DAVED@ctilidar.com>
To: 'towertalk@contesting.com' <towertalk@contesting.com>
To: <towertalk@contesting.com>
Date: Thursday, May 28, 1998 3:41 PM
>Can anyone recommend a good way of bringing antenna, rotor, and
>miscellaneous cables into the shack? My requirements are the following:
>
>1. Cables must come through the wall (not an open window) and allow for
>being able to keep the house locked and secure.
>2. I want ground all cable shields at the house entry point.
>3. Must be able to disconnect cables on the inside of the shack.
>4. Must accomodate lightning surge arrestors.
>
>How or where would I build or buy this sort of rig?
>
>thanks,
>
>Dave
>
>--
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--
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