Roger,
Here's a couple pictures of the bulkhead assembly I made for the top of my
tower...
http://tinyurl.com/rc9v2 See photo's D, E, and F.
At HF there's negligible insertion loss through a couple extra connectors.
BTW, I'm done fighting the PL-259 soldering issues and going with crimp-on
connectors for my Belden 9913 cable. I just ordered a couple dozen from
Tessco along with the proper die for my crimper. I'll see how these work
over the long run. I never was a crimp fan until I started working with
computer network cables and saw how secure the connections really were.
Also, I run my cables down the inside of the south legs to gain some
shielding from the high-noon sun.
73 de Bob - K0RC
------------------------------
Message: 5
Date: Mon, 26 Jun 2006 22:02:13 -0400
From: "K8RI on Tower talk" <k8ri-tower@charter.net>
Subject: [TowerTalk] Coax Grounding on a tower.
To: <TOWERTALK@contesting.com>
Message-ID: <008301c6998d$b62e8ba0$6400a8c0@SecondOne>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
Due to basement work I've had to pull all the cables out of the conduit.
Man, but I was sore the other day and was wondering whey until I realized
I'd pulled between 1300 and 1500 feet of cable out of conduit the previous
evening.
This has put me off-the-air with the main station which is probably why
6-meters has been open the last couple of weeks.
As this is turning into a rotator repair (It's hanging up again and the
thrust bearings are free), antenna repair, antenna removal, replace the pig
tails, and reroute the coax project I've decided that as long as the coax
has to go through connectors at the end of the pigtails at the top of the
tower I'm going to mount an aluminum angle across the face of the tower with
3" UHF feed throughs. Each of the current 4 pig-tails will fasten to a feed
through which will ground the brade to the tower at the top. The cables then
run down the inside of the NE tower leg where they are joined by two more to
the base and loop up into the junction box where they enter the 3" conduit
to the house. The cables will be jointed by at least one or two more part
way down the tower, but there may be two less from the top. The easiest is
to just say the number may vary.
My thoughts are to either use another set of bulk head connectors on
Aluminum angle bracketed to the tower as at the top, or to clamp those
brackets to the leg of the tower using a hose clamp and spacers so the
center part of the feed through will be grounded to the tower leg.
This will add one more set of connectors to the cables but from experience
and information gleaned from TT I'd say the insertion loss of the one extra
connector is going to be almost non existent. In addition the cables will be
grounded to the tower where they are leaving the tower.
The new junction box at the house entrance will be putting the shield
grounds and the Polyphasors (sp?) right outside the house at the point of
entry where they are currently just inside the house. I think this will be
an bit of an added safety feature.
One leg of the tower ground system will be entering the Hoffman box beside
the conduit, grounding the back plate inside and then continuing into the
house with the other cables. This #2 runs directly through to the house
ground for the electrical service as it's the only way I can get it there.
I'd have to tear up a rather expensive garage apron to get there outside and
that would make the grounds different length.
This is going to get rid of the conduit coming through the basement wall.
It'll come in through the end plate of the floor joists and there will be no
cables showing below the basement ceiling. At least that is the plan.
Remember it's normal for this installation to take at least three lightning
hits a year and I think it's already had it three (or more) just in the last
storm.
Any socially acceptable suggestions?
TIA
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
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