Static spark gap copper pipe size

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Original poster: "Bart McGuyer by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bmcguyer-at-houston.rr-dot-com>

Hey all,
    I'm planning on building a new TCBOR/RQ style cylindrical static gap,
but I am having trouble deciding on pipe diameter and length.  I am thinking
about using 3/4" wide and 4" long copper pipes.   The gap will be used from
1 to 2Kw.
    Also, what is the max gap size I should allow for 15Kv NST's?  12Kv
NST's?  Should I go past 0.3", or is this a waste of space?  Oh, and the gap
will be cooled by a muffin fan.

Thanks,
Bart Mc.