[TowerTalk] Buried HF/VHF feedlines

[john at kk9a.com]

When I lived in Chicago I had a 350' underground coax run of Ø1 5/8  
Heliax direct buried around foot deep and I never saw a freeze  
crushing effect.  Perhaps other soils react differently.  I am not  
sure how a conduit would help, in fact it may be worse when it fills  
with water.  Your tower company may also have surplus 1 1/4 or 1 5/8  
cable too. Don't be afraid of larger Heliax, it is not difficult to  
work with on the ground.

GL,
John  KK9A


Jonathan - KE0YBL 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