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Re: [TowerTalk] Conduit for cables to the tower?

Subject: Re: [TowerTalk] Conduit for cables to the tower?
From: "Donald Chester" <>
Date: Thu, 14 Sep 2006 17:48:40 +0000
List-post: <>
I have a run of direct-burial coax simply buried a couple of inches in the 
ground, along with my radial system.  I used to have a control cable lying 
on top of the ground, until it got sucked into a lawnmower.  I have a long 
roll of flexible black plastic (water pipe or conduit?) that I pulled out of 
a dumpster, on hand to serve as conduit if I ever decide to re-install the 
control cable.

For the A.C. from house to shack, a friend from the power company gave me a 
hunk of direct-burial aluminium pigtail wire (the stuff that carries the 
220v w/neutral from the pole transformer to the house).  But I put it inside 
PVC conduit before burying it, to protect it from accidental damage in case 
someone hit it while digging.  I rented a trencher and buried it about 3 ft. 
in the ground, so I don't anticipate anyone digging that deep on my property 
for any reason, without my supervision.

We used to have an electric stove in the kitchen, but later changed over to 
propane, so I had a spare 40A circuit.  I attached the line going to the 
shack to that breaker, since 220V@40 amps is sufficient for anything I use 
out there, including KW transmitters.  I have an additional breaker box in 
the shack with several 20 and 30 amp circuits running inside the building. I 
just made sure I linked the pigtail cable to the rest of the system using 
the proper copper/aluminium connectors where needed, including the grey 
putty stuff you are supposed to use on those connectors, and after 15 years, 
have never had any trouble with that run, and with the cable, rated for 100 
or 200 amps, the voltage regulation in the shack is excellent.

I shouldn't think it would make any difference what cables you mixed 
together inside underground plastic conduit, as long each cable has the 
proper insulation rating for the voltage it carries.  In any case, the 
cables should be waterproof, since even a perfectly impermiable conduit pipe 
could fill up with water over the years from condensation, unless you keep 
it under pressure with dry nitrogen like the heliax broadcast stations use 
to feed the tower.  My main concern is hum induced by ground loops, not 
insulation breakdown of the cables.

I also have a telephone line going out to the shack, but it runs overhead, 
using standard telephone company drop cable (another dumpster find).

I have 120 quarter-wave radials round my tower, which serves as a quarter 
wave vertical on 160 (16,000 ft. of copper wire total).  The only lightning 
damage I have ever experienced with anything associated with the 
tower/antenna system is some shattered guy wire insulators as well as a 
smoked thermocouple rf ammeter that was apparently destroyed by induction 
from a nearby strike even though the feedline was completely disconnected 
from the system at the time.

Don k4kyv


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