[TowerTalk] Buried HF/VHF feedlines

[David Gilbert]

Heliax is essentially plumbing.  Quite possibly I simply don't 
understand, but why is water a problem?  How does it penetrate the 
copper sheath?

And if water is a problem, why can't you have a hole in the conduit at 
the low spot to drain off the condensation (assuming you're below the 
frost line)?  The condensation should develop rather slowly, I would 
think, because it requires water vapor to penetrate the conduit.

Like I said ... maybe I just don't understand the situation.

73,
Dave   AB7E



On 7/24/2020 11:17 PM, Jonathan - KE0YBL via TowerTalk 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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