I don't quite understand your question.  Are you referring to a lightning arrestor - that you mount in series with your coax as it enters the building from the antenna?  Lightning arrestors ground the instantaneous voltages that may occur if lightning hits the antennal

If you are referring to a lightning arrestor in an antenna circuit, the shortest path to a good RF ground is needed.  Lightning is a series of really high amplitude square waves and all of the harmonics thereof.  in Lightning transients, there is Appreciable power containd in transients extending into the gigahertz.

A 4-0 conductor looks reactive (Usually Inductive) at frequencies above 400 MHz.  This is why wide copper strip is used in broadcast facilities.  Replace or augment the 4-0 with a 4" wide copper strip and make the run to the ground as short as possible.

Check out Harger for grounding (www.harger.com) for lightning protection equipment and supplies.

Good Luck

I rfemain,

The Old Soldering Gunslinger

OSG,

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TTFN

"...in lightning transients, there is appreciable power... ...extending into the gigahertz."

You sure about that?

Although noise from lightning can interfere with LF/MF/HF over huge distances, once one reaches VHF and above, lightning is rarely (if ever) mentioned as a source of interference.

I agree, lightning isn't a source of interference at a distance from the strike in the upper VHF and UHF range, however we are talking about protection from induced currents in a nearby strike.  I have seen the front end of KU band LNBs cleaned out by induced RF from a nearby strike.

One thing I forgot to mention is that little can mitigate damage from a direct strike.  I was a bit tired when I posted last night.  I had to drive a tower crew to the site just before sign-off, and back after the Nitrogen leak in the 6" line was identified.  The Thiokol Spryte wasn't all thet Spry last night, and I don't sleep all that well in the transmitter building.

--SGS

Just because the device that was damaged is a Ku-band device (even the 'front end'), it doesn't follow that the energy that damaged it had to be in the Ku-band.

If lightning contained significant energy at Ku-band, then these same satellite TV systems would drop sync for several seconds with each lightning bolt - and they don't.