[Towertalk] Ground wire impedance

[Steve Maki]

VR2BG wrote:

>>I also have a few Andrews hardline grounding kits that use stranded wire.

>Come to think of it, I haven't seen a single Andrew Heliax (12~13mm) grounding
>kit that _didn't_use stranded wire, all of which have been sourced new in 
>little more
>than the last ten years.
>
>I would imagine that for the typical installation, feeder lengths are such 
>that the
>length exceeds what is recommended for grounding at just each end & that
>compared to the cost of the cable, connectors & lost revenue due to down time
>more than outweigh the cost of another kit or two.
>
>Perhaps the likelihood of >1 kit in such a typical installation taking the 
>current
>makes it possible for the manufacturer to use stranded wire?

Perhaps. On cell sites, there's a lot of stranded wire used in the
ground systems - pretty much everything ABOVE the lower ground bars
is stranded. Ground kit leads, interconnections between upper and
lower ground bars, connection between the air terminal and ground
ring, etc. Ease of installation is the driving factor. 2/0 solid
would be a bear to handle! The stranded stuff IS all insulated
though so concern about corrosion is reduced.

>Speaking of grounding kits, has anyone here had any experience with a direct or
>awfully close strike with a line where the kit was fitted backwards?  By 
>backwards,
>I mean that the flying lead from the kit heads back in the direction of 
>where the
>feeder came from.  I thought cable dressing was important, but an ex-career
>Cable & Wireless guy at work says I'm nuts.  I'm tempted to put his tendency
>to drive through roundabouts in an anti-clockwise direction together with 
>the fact
>he isn't at C&W any more, but what do us hams know?  ;^)

Follow your instincts in this case :-)

The dressing of the ground kit lead is VERY important to the engineers
who design cell sites, and more importantly (to the installer), to the
inspection guys. A backwards ground kit lead = high impedance ground path.

73,
--
Steve K8LX