[TowerTalk] Hauling hardline into a 4 inch cable duct

[Gene Smar]

Keith et al:
 
     When I worked at a local electric utility company designing substations, we had a design rule of thumb for conduit.  The total area of the cables when all built out should equal 40% of the area of the conduit interior.  For Ham radio stuff (like my tower) I used 50% fill factor.  So, if you buy into that premise, your conduit should be twice the cross-sectional area of the total cables you plan to install.  
 
     One more thing:  If you have any turns in the conduit run, like at the two ends, use sweeps and not elbows.  The sweeps are larger, gentler turns (larger radius) and make pulling large cables at lot easier.
 
 
73 de
Gene Smar  AD3F

 
 


On 04/15/15, Keith Dutson wrote:

Excellent question. I wish I had an answer. I am planning to run 1 piece
of LFD4-50A and three pieces of LDF5-50A to the shack. I have heard it can
be buried, but would prefer conduit. I am now thinking 6 inch for the 30
foot run from the tower, to allow for additional cables in the future.

73, Keith NM5G

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Alan
Ibbetson
Sent: Wednesday, April 15, 2015 8:50 AM
To: towertalk at contesting.com
Subject: [TowerTalk] Hauling hardline into a 4 inch cable duct

I have a 210ft run of 4 in smooth bore plastic cable duct going in a
straight line 3ft underground from outside my shack to a small shed at the
base of my tower. There is a brick-built man hole (aka inspection
chamber?) 3ft x 2ft 6in at each end.

Presently I have LDF2-50A in the duct but it's a tad lossy and I have the
option of some LDF4-50A or LDF5-50A coax.

I have a draw rope running through the duct and a pulley set into the floor
of the man hole each end just outside the duct opening but I am wondering
how easy it is doing to be to pull either of these thicker and heavier
cables into the duct?

How do you guys at big stations do it? Will 3/8" polypropylene draw rope and
a strong young man (ie not me!) be able to do the job, or are we looking at
steel wire rope and a power winch?

Thanks,

Alan G3XAQ
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