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 ?
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|