[TowerTalk] from towers to shack

[Joe Subich, W4TV]

> Consider a direct strike to the tower? The cables being above or
> below ground don't materially change the voltage waveform, at least
> as selection of the suppression devices are concerned: it's kilovolts
> you need to deal with.

Cables "tapped" to the tower are coming off a voltage gradient from
several hundred KV at the top of the tower to zero at ground (if the
tower is properly grounded).  At 10 feet on a 100 foot tower, one had
several 10s of KV .. not easily dealt with using simple devices.

> Conventional transient suppression techniques work for phone and
> power lines, which run above ground for miles.

Phone and power lines are not connected to lightning rods several
times the height of the lines.

73,

    ... Joe, W4TV


On 12/8/2013 11:59 PM, Jim Lux wrote:
> On 12/8/13 8:46 PM, Joe Subich, W4TV wrote:
>>
>>> I think as a practical matter, whatever transient suppression you do
>>> at the entrance to the shack is going to be the same whether the
>>> cables are laying on the ground, suspended 10 feet off the ground,
>>> or buried a couple feet deep.
>>
>> Not if the cables are coming off the tower 10 - 15' high unless one
>> has a grounded metallic "cable bridge" above the cables and connects
>> the cable shields to the bridge/tower where they leave the tower.
>>
>> With cables exiting the tower some distance above ground, the lightning
>> protection at the shack entrance will be much more critical.
>>
>>
>
>
> But what would you do differently, transient protection wise?
>
> Consider a direct strike to the tower?  The cables being above or below
> ground don't materially change the voltage waveform, at least as
> selection of the suppression devices are concerned: it's kilovolts you
> need to deal with.
>
> A strike right to the cables? Is that particularly likely, given that
> there's a tall tower and a not as tall house next to it?
>
> Conventional transient suppression techniques work for phone and power
> lines, which run above ground for miles.
>
>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>