[TowerTalk] Coax, conduit and toroids

Larry Loen lwloen at gmail.com
Tue Jun 26 20:01:48 PDT 2012

> What should I do to help ensure that the inside of the conduit stays dry? Is
> applying some sort of weatherproof sealing compound to each end enough?

This is a problem that concerns me as well.   "Up the Tower" suggests
that you not try and keep it totally dry.  It suggests you use drain
pipe to let moisture and condensation seep out of the bottom.

In my case, I don't really have a direct shot to the tower (for
reasons that I needn't bore you with, there's a shed between me and
the shack and other problems like the septic system, too).

One thing I'm considering is 4" plastic sewer pipe that comes to
something like a small manhole (probably made of plastic) that I will
seal from the top.  That "manhole" would be deeper than the conduit.
It will allow moisture to collect as well; maybe I can even have a
"breather" in it.

Still thinking this one through.  Absent that, I'm not so sure that
drain pipe isn't the right idea, even in Arizona.

If I'm grounded properly at the tower and the shack, I don't think
that using PVC conduit is critical.  (Wrong here?)

> I'm planning two coax runs and two control cable runs, in two separate
> conduits, coax in one, control in the other. What's a reasonable diameter
> and turning radius for the conduit? The Times Microwave
> specifications/limits are one thing, but I also want to do what I can to
> ease/simplify the process of pulling the coax through the conduit once it
> gets installed.

There is pipe that takes about a 120 degree bend and if you put in two
short lengths of straight pipe, you can get a fine turning radius out
of that.

At the IBM radio club in Minnesota, one thing they also had was about
a 3/16 inch ordinary cable (think: thin guy wire) that was right
alongside the coax.  You had a second one in the shack and so you
could (or so it was planned; never saw it done) pull a new coax
through long after the burial and then have the alternate cable come
right along with the new one which becomes the new one stored in the

In my case, I'm planning 4 inch pipe precisely to ease the question of
servicing the buried cable.  I want a halfway decent shot at replacing
or even adding something after I have it all buried.  The
junction/manhole idea, which is a kind of necessity anyway, would also
be at about the halfway point, which would ease the process as well.
Or, so the thinking goes for now.

Anyone got better ideas?  I'm really interested in this problem.

> Are there any precautions I should take with regard to running the coax or
> control lines near existing electrical wiring for the house? I'm trying to
> avoid proximity as much as I can, but I'm wondering how far I should go.

My plan is to run the coax and the AC to the tower very separately.

But, I also am not 100 per cent sure (and don't know if I can find
out) where the power into the house goes from the power company's
meter (easily visible) to the electrical breakers in the house (which
is all the way on the other side of the house sorta kinda parallel to
my planned cable run).  If it is under the mobile home in question,
I'm fine.  If not, I'll have to deal -- carefully -- with the
crossover and maybe for the feed from the house to the septic as well.

My basic plan is to go well under both -- six inches to a foot
minimum, I hope.  Not just for cross talk, but for basic mechanical
and electrical safety.

That is something that depends on the facts "in" the ground.  I may
have to adapt a bit on the fly, here.

Larry Wo0Z

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