[TowerTalk] Cable Feed Thru for Removable Cables

[Ian White GM3SEK]

Barry Merrill wrote:
>
>
>Work is close to completion on the ham shack at EI/W5GN, and I need
>suggestions on how to create a feed thru for the RF and Control Cables for
>the antennas and (eventually) tiltover tower.  They will be pulled thru only
>when we are here and will be removed and the feed-thru sealed when we're not
>here.
>
>The concrete wall is 14 inches thick, and my contractor says he can easily
>drill a 3 inch hole thru that wall, about
>12 inches above the ground level.
>
>I need about 3 inch diameter so the DB25 for the BigIR controller can be
>pulled thru, but the actual cable cluser will probably be only about an inch
>in diameter, as I'm strictly low power from here.
>
>So my concerns are:
>
> a. How do I "seal" with something that is removable
>    when the cables are in place to prevent wind-driven-rain
>    and the wind noise (we are on a bluff on the Atlantic).
>    I thought (briefly) about using expandable foam, but
>    past experience suggests it would NOT be easily removed.
>    Rags seems to be the current thought.
>
> b. How do I seal the "hole" when we're not here.
>    I've though about using a threaded pipe with caps
>    both inside and outside, but don't know how
>    reusable the threading will be, especially exposed
>    to the salt water environment.
>
> c. Assuming a metal pipe is use, is it important to
>    bend the outer end downwards, or will horizontal
>    work?  I don't think PVC pipe can be threaded and
>    be reused?
>
Welcome to the Wet Coast of Europe, Barry. The main cable entry here is 
in a similar exposed situation.

First of all, don't use a large diameter unless you absolutely have 
to... and it seems like you don't, really.

A DB25 connector will easily go through a 40mm PVC waste pipe (like you 
almost certainly have under the sink) if you remove the shell first. You 
might even be able to find a low-profile side entry connector shell that 
will go straight through.

Your plumbing contractor knows all about 40mm sink wastes. There's a 
wide range of push-fit pipe fittings available, for example:
http://tinyurl.com/3b6kys

If you thread all the cables through a 90deg sweep bend before attaching 
the connectors, you will then be able to thread the cables through the 
straight pipe, one by one starting with the DB25, and finally push the 
90deg bend onto the end of the pipe. When you're away, there's a thing 
called a "socket plug" that will push into the open end.

Wind-proofing when you're in residence is a bit more tricky, but some 
gaffer tape around the downward-pointing mouth of the 90deg bend should 
do it.


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek