Power lines and coaxial cables buried underground must be kept at
least 36" apart per NEC code to prevent the possibility of a power
cross. Usually in a common utilities trench, the power cable is
buried first, followed by telco, followed by cable TV. This is so
the telco and cablet TV people won't "disturb" the power cables
when locating a problem. The 36" is
(if memory serves) for the standard 220/440V
delivery system and becomes
greater as the voltage increases. This distance can be
in the vertical, horizontal or diagonal plane.
73,
Bob AA0CY
----------
From: W8JI@aol.com[SMTP:W8JI@aol.com]
Sent: Saturday, July 04, 1998 8:33 AM
To: towertalk@contesting.com; hotrodhamshack@juno.com
Subject: Re: [TowerTalk] Fwd: Advice on coax & power lines in same underground
ditch.
In a message dated 98-07-03 16:15:40 EDT, you write:
<<
Good Day
This coming week I have the opportunity to install my coax conduit in
the same ditch with the power feed comings to my house. The ditch will
come within 10' of my tower. The question, how close can I get to power
lines without getting 60 cycle hum etc.? Any advice on this would be
appreciated
73
>>
AC power will never modulate RF signals, unless there is a non-linear device
(like a diode or transistor) involved. I run 80 volts AC and audio control
tones right down the coaxial feedline's center conductor of low noise
receiving cables, and also 28 volts AC down my heliax to a remote switch box,
with absolutely no ill effect.
When each individual system is properly installed, the power wires and coax
can be bundled as close as you like without any problem.
When the feedlines are improperly installed, a specific simple answer is
impossible to give since it could create a variety of problems.
73 Tom
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