[time-nuts] Lightning arrestors for GPSDO antenna

Dave M dgminala at mediacombb.net
Thu Oct 16 22:51:09 EDT 2014

Thanks, Chris.
I've done a bit or research on the subject, and think I have a reasonable 
grip on the necessary steps.  I have an 8' ground rod driven into the ground 
directly under the spot where my antennas mount.  #6 solid copper from the 
rod to a heavy aluminum plate, where the arrestors will be mounted.  A #6 
solid copper wire from the plate to the antenna mounting structure.
I will also have an arrestor at the antenna input of each GPSDO unit, which 
will be mounted on a 2" wide copper strap, which will be then run to the 
outside ground rod with a doubled 1" wide copper braid.
I realize that extremely low ground resistance is fantastic, but I don't 
have access to a ground resistance set, so I'll have to accept what I have 
and accept the consequences if something happens.  A second ground rod isn't 
out of the question, but will have to wait until my broken wrist heals so I 
can swing a sledge hammer.

I'd still like to hear comments on the effectiveness of gas discharge type 

A question has bothered me for a while, but can't find a definitive answer. 
Should I enclose the antenna feedline in metal conduit or nonmetal conduit? 
I've seen documents that state that metal conduit is the best way, and 
others stating that metal conduit shouldn't be used     Anyone have a good 
answer  (talking about antenna feedline; not the grounding wire)?

Dave M


Chris Albertson wrote:
> Lightening arrestors are an important part of a protection system but
> just installing some in the antenna cable is not going to help so
> much.  You need a system approach.  If you do it right you can take a
> direct hit
> The big problem with grounding is Ohm's Law.  That is if any current
> flows in a conductor that has resistance there will be a voltage
> across the conductor equal to the current times the resistance.  But
> with lightening you can have 100,000 amps of current in a ground
> wire.  If that wires has
> 0.01 ohms of resistance you have 1,000 volts above true ground on your
> "ground" connector on the lightening arrestor.  Your ground is no
> longer at ground.
> You need some very tiny resistances and to get that you are going to
> need to do things like using multiple ground rods and large
> conductors.  And connecting grounds together.
> On Thu, Oct 16, 2014 at 4:34 PM, Dave M <dgminala at mediacombb.net>
> wrote:
>> I'm looking for effective coaxial lightning arrestors for my GPSDO
>> antennas.
>> I've seen several types; those completely enclosed in a one-piece
>> metal enclosure (no replaceable components) and those having a
>> replaceable gas discharge tube seem to predominate the list.
>> I'm looking closely at the gas discharge tube types, and am curious
>> as to their effectiveness and durability.  I'd like to know stuff
>> like; are they effective in dissipating a static charge, how do I
>> know when the gas tube needs to be replaced, are the gas tubes of a
>> special type, are replacement gas tube easily available, etc.
>> I'm interested in opinions and experiences with arrestors and
>> recommendations for which type is most effective.
>> Thanks for comments,
>> Dave M
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government fears the people, there is liberty -- Thomas Jefferson

Dave M 

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