Topband: underground cables question

Thu Oct 5 10:12:04 EDT 2017

Coming from an ancient Telco background which included keeping microwave
waveguides dry for AT&T, unless you are willing to pressurize the conduit
at one end and allow air to exit at the other, AND insure that the air is
dry enough to not condensate at your coldest possible ground temperature,
or run it with an unbroken slope to a point where water drains without
pumping and or can be suctioned, then make these assumptions:

1) Permanent performance and very long life is desired and outweighs cost.
If you move a lot and are putting up stuff at rental housing you probably
need not worry. Just remember to start with new coax and cable at the new
rental place. Throw away the old stuff. Then mark this read and move on to
the next posting. If you think you are retiring at your place of residence,
and if lucky want it to work without a worry for the next 30 years absent
direct lightning strike, then read on.

2) All conduits will fill with water. That is their NATURAL state unless
you specifically and effectively mitigate it. At any time other than first
installed, filled with water is their most probable state.

This leaves the main usefulnesses of the conduit as

a) Critter protection, and

b) Cable replacement, if the conduit is large enough and water-proof pull
ropes are left in conduit,  a method of adding or replacing cables that
avoids redigging and leaving deprecated cable in the ground. These are
significant long-term advantages, and many find those more than enough
reason to use them. However.......

3) Even in conduit all cables must have permanent, water-proof jacketing.
Most cable has jacketing that is not rated for permanent submersion, meant
for indoor use.

Polyethelyne (PE) jacketed or hardline cable is really the only commonly
available choice for coax with portions permanently submerged. Flooded is
nice, but probably overkill INSIDE CONDUIT if the jacketing is PE or other
permanently waterproof material. ***RG213 does NOT conform.*** Any
miscellaneous plastics do not conform. There are cables manufactured with
ham-uncommon materials to telephone company specifications, FOR DELIVERY TO
TELCO, that have all the water stuff worked out just fine. But BEWARE
knockoffs and batches for retail that mfr knows will never be sample tested
by telco. Or for that matter cable that failed telco tests and was put on
the retail market to recover costs.

High current rotator motor leads (as opposed to control leads) should use
the commonly available UG series direct-buriable power wiring available at
home improvement stores. Less voltage drop, permanent and rated for wet
environments.

4) splices or cable terminations should be made indoors and elevated where
waterproofing failure will not allow water to get inside the PE jacketing.
Some manufactured multiconductor cables will have BOTH external and
internal insulation PE or teflon. Do not locate splices in conduit. You're
just asking for it. Even if 9 out of 10 get away with it, be assured you
will be # 10. Murphy KNOWS all you've done, knows all the contest and
DXpedition dates, AND has a malevolent nature.

73, Guy K2AV

On Thu, Oct 5, 2017 at 8:49 AM, Dale Putnam <daleputnam at hotmail.com> wrote:

> I agree with Ken, with only one option, and that would be if the conduit
> is open on both ends.. allowing free air flow thru. That situation, MAY
> help dry the water from sitting on the cable, depending on the average
> humidity at the underground temp. Warm air from inside.. to cold air
> outside may not work out well either.
>
>
>
> Have a great day,
> --... ...-- Dale - WC7S in Wy
>
> "Actions speak louder than words"
> 1856 - Abraham Lincoln
>
>
> ________________________________
> From: Topband <topband-bounces at contesting.com> on behalf of Ken Claerbout
> <k4zw at verizon.net>
> Sent: Thursday, October 5, 2017 6:19 AM
> To: topband at contesting.com
> Subject: Re: Topband: underground cables question
>
> As you have found out, it's impossible to keep water out of a conduit like
> that.  I use direct bury cabling and put it directly in the ground.
> Granted the cable is flooded, but putting in back in the conduit ensures it
> will sit in some water, something I would try to avoid.
>
> 73
> Ken K4ZW
>
>
> -----Original Message-----
> From: John <beaumonts at beaumonts.karoo.co.uk>
> To: topband <topband at contesting.com>
> Sent: Thu, Oct 5, 2017 4:11 am
> Subject: Topband: underground cables question
>
> Hi all, some  years ago I buried a 4 inch conduit about a foot deep in my
> field , inside I run a control wire and a coax line RG213 to a 160 m
> vertical the feeder was a total of 5/4 wavelength long about half of it in
> the conduit, it was used as one line for a pair of verticals spaced 5/8
> wave apart. When first installed it worked very good but after a while I
> noticed it dropped off and I suspected water ingress. An insulation test
> with 1000v from my electricians test equipment showed indeed a fall in
> insulation resistance.
>
> So my question is I have a couple of large reels of commscope F1160 BEF
> flooded 75 ohm
> do you think I could put it in the same conduit which has allowed some
> water in or would you make alternative arrangements . I realise it a direct
> bury coax but appreciate advice.
>
> I wish to get the two verticals going again will use 1 X 3/4 line above
> ground 1x5/4 line part in conduit and a 1/2 wave to switch in and out above
> ground.
>
> regards
>
>
> John Beaumont
> G4EIM
>
>
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