[time-nuts] Lightning arrestors for GPSDO antenna

Jim Lux jimlux at earthlink.net
Thu Oct 16 23:00:46 EDT 2014

On 10/16/14, 6:27 PM, 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.

For lightning transients 1 us kind of rise times...inductance is a MUCH 
bigger deal than resistance, and inductance is very weakly dependent on 
conductors size and shape.

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