> From: Kelley <kshaddrick@jetup.net>
> Subject: [TowerTalk] Rohn HDBX Advice
> To: TowerTalk@contesting.com
> Message-ID: <4C6DB797.3070207@jetup.net>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> I just put up a Rohn 48' HDBX tower. Before I start putting up antennas,
> I want to add some more grounds to the tower. The current bolts that
> hold the tower to the base are not long enough to add another nut so I
> can attach the ground wire. I've been unable to find any longer bolts
> that will work as the unthreaded length of the longer bolts is to long,
> thus I hit the end of the thread before they are tight.
Wouldn't the addition of a washer or two make up the additional
shank-length to get you to where the bolt will tighten up against the
leg and still have sufficient excess for your ground lug?
Another trick I've used in the past is to buy a hex "union" style nut
that you can thread on to what little exposed threads you have (you do
need a couple, of course) and you then put a second bolt into the nut
from the other side. In this manner, you could add on any number of
additional connectors, just by going to a longer secondary bolt.
I am particularly interested in this topic - my 40' HDBX base was
finally poured over a week ago, and I'm itching to start stacking
sections and adding the grounds and antennas and so on.
I was planning to add a few more holes as needed - mine has already been
painted once, and the PO drilled a few holes on his way up, since the
rotator is ground mounted and the mast runs all the way to the top -
there are holes drilled every 10' or so for 3/8 all-thread that goes to
"thrust shaft" (it's not a bearing, just larger diameter tubing that
goes around the mast) supports. The very top sports a real thrust
bearing, of course. These "supports" shouldn't contact the mast under
normal use, but would keep it in line if it wanted to bend.
So, mine already has holes, though it's important to apply paint to
prevent corrosion, since the galvanizing is compromised at any scratch
or drill point.
I'm also thinking of perhaps adding a few holes of my own at the top, to
bolt on a few pieces of aluminum angle. They will be shimmed away from
the (painted) tower with stainless steel washers and bolts to avoid any
galvanic action, but would likely require a couple of new holes near the
top. I may get away with using the rotor shelf mounting holes.
The angles would be to secure the bulkhead connectors at the top
termination of the heliax before going to LMR400UF, and would double as
the stand-offs for a dipole and shunt feed wire.
-Tom
ke7vux
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