[TowerTalk] from towers to shack

[Roger (K8RI) on TT]

On 12/8/2013 9:37 PM, Steve Maki wrote:
> On 12/8/2013 8:29 PM, Jim Lux wrote:
>
>>> my question is about which is TECHNICALLY the best option, if there 
>>> is a
>>> technical benefit or about RFI to put them under ground. If there's no
>>> advantage, is much easier to manage the cables OVER the ground
>
>> Mechanical protection is what's good about underground.
>> There's not a lot of practical difference from an RFI standpoint (either
>> can be good or bad..)
>
>
> I always assumed that common mode currents should be at least slightly 
> attenuated by the surrounding earth, but maybe not...

Although being in conduit reduces the capacitance to ground, on a 
several hundred foot run it's still substantial. I'm not sure about 
common mode, but it certainly reduces the pulse amplitude reaching the 
shack from a lightening strike, or nearby strike.

Direct burial cable would have considerably more capacitance to ground.  
I've never measured it, but "I'd think" it would be quite noticeable at 
reducing common mode to ground through HF.  It seems intuitive, but that 
"I think" means I don't know for sure.

73

Roger (K8RI)

>
> -Steve K8LX
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