[TowerTalk] Lightning protection

[Jim Lux]

On 7/8/13 5:28 AM, Pete Smith N4ZR wrote:
> My answeris simple - It is not cost-effective. They are using extensive
> lightning grounding at the tower base, and purpose-built transmitter
> buildings with elaborate grounding systems. 24/7/365 costs.

Exactly..
They are also facing a very different cost/benefit analysis than the 
typical ham.  They pay a LOT more for the assembly and construction 
labor than most hams do, so something like using AWG 2 instead of AWG 6 
doesn't make a lot of difference in the overall construction cost.

And, their "cost of non-availability" can be substantially higher.  If 
an FAA control tower is off the air, that's a big problem and it gets a 
lot of attention.


> ask me whether a direct strike while connected would result in <5 volts

That's the other thing.  Equipment designed for 24/7/52 kinds of usage 
tends to be more rugged, and it tends to be "single frequency".

  Ham receivers, for instance, don't do things like put clamp devices on 
the receiver input for overvoltage protection, because it degrades the 
IMD performance with strong signals.  A commercial operation can put a 
big notch or bandpass filter to knock down that strong AM station, but 
that doesn't work when you want to tune over the entire HF band.

Equipment made for this application also tends to be more robust for the 
data and control and power connections. You won't see a connector with a 
pin connected directly to the microcontroller inside, like you do in 
cost sensitive ham gear.  It will go through some sort of buffer, most 
likely with decent transient suppression, at the cost of perhaps slower 
data rates (and significantly more money).





>
> On 7/8/2013 8:06 AM, Jim Thomson wrote:
>> Ok, I’ll bite.   What do AM /FM /TV broadcast folks do or use for
>> lightning protection ??
>> Esp with real high towers involved in some cases.   They don’t shut
>> things off and toss cables
>> out the window.   And ditto with cell sites and microwave sites.
>> They are all left on 24-7-365.
>>
>> IE: what do the big boys use ?   Why not copy their procedures ?
>>
>