Topband: underground cables question

Thu Oct 5 11:00:19 EDT 2017

I love it!  Murphy should have a price on his head!

Chuck W5PR

On Thu, Oct 5, 2017 at 7:13 AM Guy Olinger K2AV <k2av.guy at gmail.com> wrote:

> 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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