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Author Topic: 100 watt air gap lightning arrestor????????  (Read 2290 times)
VOODOO42
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Posts: 114




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« on: February 28, 2009, 04:23:58 AM »

I was wondering what will happen if you run more than 100 watts through one of those cheap air gapped lightning arrestors. Will it dameage your amp, radio, tuner etc..... will it destroy the lightning arrestor itself or will nothing harmful occur.

Thanks for any input,
voodoo 42
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AA4PB
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Posts: 12980




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« Reply #1 on: February 28, 2009, 06:16:04 AM »

The issue is not the power, but rather the voltage at the point where the arrestor is inserted. If that point is 50 ohms then 100W would produce 70V (P = E*E/R). If you have 50 ohm feed line with an SWR other than 1:1 then the impedance at the insertion point could be something other than 50 ohms and the voltage could be much higher.

The arrestor needs to be set to fire at a much higher voltage than you are likely to see during normal operation. If the arrestor fires then you surely risk damage to the transmitter.
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K9KJM
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Posts: 2415




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« Reply #2 on: February 28, 2009, 11:41:13 PM »

Most of those cheapo gap type "arrestors" are rated at well over 100 watts, And should be good for well over 100 watts into any kind of half way matched antenna load.  (All that is inside them is a internal star type lock washer!)

But if I had one here, I would simply take it out of line and toss it in the garbage can. OR better yet, Turn it in to some spare cash by selling it on some CB swap board!!!!!
(They really do not do much of anything for lightning protection)
MUCH better protection would be had by simply doing a good job of bonding your coax shield to a good ground system right where it enters the building.
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AF6IT
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Posts: 26




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« Reply #3 on: March 05, 2009, 12:36:50 PM »

Most solid state finals and receiver rf stages will be toast long before that thing fires off! Better to get an ICE unit or maybe Polyphaser. Heck, if you're too cheap or broke at least find a way to earth ground your center conductor using a 100k ohm non inductive resistor. It will help bleed off the static before it can build enough to toast anything.

Stu AF6IT
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