[TowerTalk] lightning protection

[Roger (K8RI)]

Richards wrote:
> Is there any reason one would not want to put protective devices at BOTH 
> the tower AND the entry point?
>
> Unlike wearing belt and suspenders... it might be a good idea...?
>   

I make it a point to ground the coax shield at the top and bottom of the 
tower.  As all antennas are at DC ground it's unlikely the voltage from 
the center conductor to shield will get tremendously high. 

Placing an additional polyphaser at the base of the tower shouldn't hurt 
anything, but spikes on the line may reach several times the amplitude 
compared to  where they ender the house due to line capacitance and 
inductance. I might want to use one of the spark arrestors there in 
conjunction with a polyphaser at the house entrance.  The protection at 
the base of the tower should work, but it's likely that there will be 
far more pulses there that will cause the device to conduct than at the 
house entrance. This should raise the likely hood of the devices failing 
more often at the base of the tower than the same type of device  
located at the house entrance.  They still protect the equipment, but 
when one fails you are off the air, plus they cost over $50 each.

Having said all that, I view lightning protection as a crap shoot.   
Take one of the so called super strikes and not much can protect your 
equipment as you not only have the direct voltage and current coming in, 
but a tremendous pulse induced into the wiring in the house be it coax 
(TV or rig), telephone, cable, internet, AC mains or even water well. 
Which reminds me, grounding the antenna system to the well isn't a real 
good idea if you use a submersible, deep well pump.  They are work to 
replace if you do it your self and the pumps aren't cheap. OTOH if you 
have to hire a rig to come in and pull it, that can be expensive. I've 
known of quite a few burnt out submersible pumps due to near by strikes, 
let alone direct hits.

73 and again, good luck,

Roger (K8RI)
> ===============  K8JHR  =====================
>
> CRAIG CLARK wrote:
>   
>> "Techs from Poly Phaser said at the base of tower, "
>>
>> In most ham installations, however, the towers and antennas are often some
>> distance away 
>>
>> That's why I have all my protection where the feed and control lines enter
>>     
>
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