[TowerTalk] Buried HF/VHF feedlines

[Kevin Kidd]

A few observations...

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.

Good luck,

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 1:26 AM Jonathan - KE0YBL via TowerTalk <
towertalk at contesting.com> wrote:

> Hi All,
> I feel like this has been done to death - and yet, the Internet has really
> been notoriously awful with misinformation for me the past few weeks. I
> appreciate your thoughts as I work through this!
>
> I'm putting up a new tower primarily for HF and maybe some VHF. Given my
> ideal location is some ~350ft+ from the shack, I've been waffling back and
> forth as to whether to remote the radios in an enclosure, or bring Heliax
> back. I'm leaning toward the Heliax route.
>
> I'm working with an experienced (decades) climber/tower company in my area
> (Minnesota), who has used 7/8" Heliax for $1.50/ft. This seems reasonable,
> and a fraction of new, thus making my project seem doable. Sadly may
> require an underground splice due to lengths, but one battle at a time. I'm
> open to other sources for such things.
>
> Herein lies the rub -- my climber's experience has been (and probably
> yours as well) that directly burying this in our frozen tundra eventually
> results in crushed cable through thawing and freezing. I'm considering 3"
> or 4" HDPE conduit/innerduct to alleviate that, but given I'll need to go
> through a valley, condensate will condensate in the dip no matter what I
> do. I could perhaps drop the conduit down 36+" deep to avoid the frost
> level, but it'll still be sitting in water (albeit not frozen at that
> depth) without active moisture management in the run (fan, nitrogen (ugh),
> whatever - not feasible).
>
> I feel like at this point I'm really overthinking it. Fiber to the tower
> and radios in a box would be much easier, but less desirable - but now I'm
> really torn.
>
> I appreciate your feedback immensely,
>
> Jonathan
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