[TowerTalk] Buried HF/VHF feedlines

[Kevin Kidd]

Good points but I have dug up too many failed attempts at below grade
waterproofing to go with anything less than my original statement.   Giant
warts of butyl and miles of  tape, PVC pipe pumped full of silicon sealer
down to a couple wraps of Dollar Store black tape,  Some lasted years, some
failed the first time that the water table came above the cable.  The key
is that  they all failed.   I'm sure that there are below grade splices
that remain dry but the odds aren't very good and I'm a nervous bettor.

If I were going to be FORCED to do an underground splice, I would probably
use one of the resin waterproofing kits designed for buried telco cable
that is a mold placed around the cable and poured full of a 2 part resin
sealer.  The resin gets hot and infiltrates everything.  If it bonds to the
cable half as well as it does to your hands, it would probably work for a
long while if the water pressure weren't too high.  It would have to be
direct buried because those things are fairly large even with a smaller
cable.

Regards,

Kevin C. Kidd, CSRE/AMD   -  WD4RAT
kkbclists at kkbc.com <kkidd at kkbc.com>
Lawrenceburg, TN
KK Broadcast Engineering   -   AM Ground Systems Company
www.kkbc.com  --  www.amgroundsystems.com


On Sat, Jul 25, 2020 at 9:50 PM Steve Maki <lists at oakcom.org> wrote:

> Gotta push back on the conclusion here. I would replace the "splices
> should never, ever, ever, ever, ever be placed below grade or in a
> flooded conduit" with something like "should never be placed in a
> conduit and under ordinary circumstances should not be placed below grade".
>
> A waterproof splice is EASY, but it results in a big bulge in the cable,
> which not only makes THAT cable hard to pull in and have confidence that
> you have not damaged the splice, but any others that you might want to
> pull in at a later date would be problematic.
>
> Not only that but by the time you buy the extra connectors and spend the
> extra time doing a proper weatherproofing job, why not just beg borrow
> or steal a long enough cable to begin with.
>
> But it's certainly possible using a number of different methods to make
> a coax splice that will survive UNDER water indefinitely. The legacy
> cellular industry MOP using a big glob of hand molded butyl rubber with
> multiple layers of stretched vinyl over the top with each layer
> extending further and further past the butyl, will create an area that's
> more impenetrable than any other place along the cable. You can take
> that to the bank.
>
> -Steve K8LX
>
> On 07/25/20 19:55 PM, Kevin Kidd wrote:
>
> > Splices are "weather proof" not water proof and should never, ever, ever,
> > ever, never be placed below grade or in a flooded conduit.  They will too
> > often leak hanging on a tower, they will always leak underground /
> > underwater.
> >
> > I have pictures of 3in Air Heliax compressed to about half that diameter
> > after freezing in a shallow, water filled, steel conduit in a MN swamp.
> >
> > Hardline is waterproof and direct burial as long as it hasn't been
> spliced
> > or damaged.  Bury the coax or conduit below the local frost line and
> don't
> > splice it and you will be good for years.
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