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Re: [TowerTalk] Recommended Coaxial Surge Protector for HF

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Subject: Re: [TowerTalk] Recommended Coaxial Surge Protector for HF
From: Rick Stealey <>
Date: Sun, 2 Jan 2011 16:43:55 +0000
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You can easily check your lightning arrestor with a resistor and HV power 
Use 500k-1 meg in series with the + lead.  This will limit the current to 1 ma
if the voltage is 1KV.  Put a voltmeter across the antenna input side.
In other words the positive lead of the power supply goes to a 1 meg
resistor, then to the center pin of the coax connector where the 
antenna normally plugs in.  The case of the arrestor goes to the case
of the PS.  A voltmeter is connected from the resistor to ground.
You will see the voltage across the arrestor in the range of 200-700 volts
if the gas tube is ok.  If the voltage is the same as the PS (say 1000 volts)
then the gas tube is not firing (has opened up).
If you have a variac and can therefore increase the voltage slowly you 
will see it come up into the range of 700 volts (for a legal limit arrestor) 
and then suddenly drop down to around 200 volts.  The absolute values of 
these voltages are approximate.  The equipment side of the arrestor is
left un-connected during these tests.
All that is inside the Polyphaser arrestor is a gas tube to ground and a little 
ceramic capacitor in series with the shack side.  When you look up replacement
gas tubes on the Mouser site and see they only cost $2-3 you just "might"
get a little sick, especially if you bought a bunch of them for $60 each!
While you have it open put a 1 meg resistor to ground across the gas tube.
This will constantly drain the static off, never letting it build up to where
it fires the gas tube or damages your rig.  I suspect your capacitor may also
be defective because it should be blocking that charge.  Also the capacitors
in the low pass filter are likely damaged because they shouldn't be arc'ing.
I homebrewed my own protection using the above techniques and don't
have any static buildup.  But I haven't been hit with lightning yet either!
If you perform the test, do it with the equipent side unterminated.  Then
repeat with the low pass filter connected.  If the results differ then you
have a defect in the capacitor or the LPF.
Rick  K2XT


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