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Richard Clark · November 30th 06, 12:01 AM posted to rec.radio.amateur.antenna

On 29 Nov 2006 14:17:29 -0800, wrote:

You forgot to tell him about trimming the folded back coax shield in
order to account for the reduction in velocity factor. The folded back
shield and the coax outer shield have a dielectric constant between
them that is based on the cable jacket material and a minimal air gap.

You covered this quite well in an earlier post you made:

Hi Roger,

I took a quick glance at your link, but I don't think I paid much
attention to velocity factor (given all the variables). For all of a
life of precision I've been devoted to, I can summarily toss off those
issues (when data has already pounded me down with the weight of
imponderables).

One way to approach this is to take SWR readings with the progressive
rolling back of the shield over the lower jacketing. If someone could
do this with a stepper motor, then we would have a new antenna design
(new in the sense that it's new to/from me, and probably anticipated
looooong ago).

73's
Richard Clark, KB7QHC