On Wed, 13 Sep 2006 21:35:52 -0400, Alan NV8A wrote:
>I have questions about the best way to get cables (coax, AC, and
>control) from the shack to the tower.
First, use TWISTED PAIR for all control cables and for power. This
minimizes crosstalk/noise to control lines. Don't bother with
shielded cable -- cable shields provide NO magnetic shielding, and
virtually all coupling below 1 MHz or so is magnetically coupled.
Twisted pairs also reduces the coupling at RF.
Second, I wouldn't be so quick to dismiss the importance of steel
from a lightning protection point of view. A lightning hit will
cause a lot of current to flow in the earth, far from a perfect
conductor, and significant potential differences will be created.
Polyphaser is in that biz, and has certainly studied it more
carefully than most of us.
Third, I fully agree that the price of the conduit itself is a
small fraction of the total cost of the conduit system, so if
steel is safer (as Polyphaser says), that's the way to go. Yes, it
Fourth, I read the code the same way that Jim Lux and Phil Camera
do with respect to the separation of power and low voltage wiring.
Fifth, I see NO problem running control lines with the coax.
And finally, the code rules about the number of bends ARE related
to ease of pulling and damage as a result of pulling. And it's the
number of bends between accessible pulling points that is what
Jim Brown K9YC
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