Topband: underground cables question

Thu Oct 5 11:12:45 EDT 2017

must have to do with the annual rainfall.

I too come from 30+ years in telco and radio comm. There are 12 runs of 6 in conduit between building on one campus, and a number of others around that are still dry after being there for 20+ years. And the conduit, I am speaking of is PVC TUBE..   pretty much the same stuff that carries the water into your house. IF someone wants to use emt conduit, then that is the description that Guy so aptly describes. NOT a good deal. AND it isn't rated for water per code in the electrical code either. I have seen where squirrels somehow managed to work the metal conduit hard enough with the weather helping, to access the coax inside.. they didn't much like the sticky goo inside.. but that didn't stop them from eating enough to short the coax..   and of course Muphy made it an intermittent short.

Have a great day,
--... ...-- Dale - WC7S in Wy

"Actions speak louder than words"
1856 - Abraham Lincoln

________________________________
From: guyk2av at gmail.com <guyk2av at gmail.com> on behalf of Guy Olinger K2AV <k2av.guy at gmail.com>
Sent: Thursday, October 5, 2017 8:12 AM
To: Dale Putnam
Cc: topband at contesting.com
Subject: Re: Topband: underground cables question

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<mailto: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<mailto:topband-bounces at contesting.com>> on behalf of Ken Claerbout <k4zw at verizon.net<mailto:k4zw at verizon.net>>
Sent: Thursday, October 5, 2017 6:19 AM
To: topband at contesting.com<mailto: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<mailto:beaumonts at beaumonts.karoo.co.uk>>
To: topband <topband at contesting.com<mailto: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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