Gee what are these "feet" things? grin (I use 300/f for free space -
for metres)

Velocity factor in coax is vs free-space. If you are using these numbers
for calculating tuned lengths keep in mind that the manufacturing
tolerance for velocity factor is not real accurate and you should
cut/tune with a GDO/TDR etc.

From my reading I have seen dipole end effect vary between 90 and 98%.
Almost always a function of length/diameter ratio.

Cheers Bob VK2YQA

Tac wrote:
I know free space half wave dipole length in feet is 492/f mhz.
I also know 468/f mhz is for "antenna cross section...stray
capacitance...called end effect because the ends of the antenna are
made farther apart electrically than they are physically..." as laid
out in the "Practical Antenna Handbook 3rd edition p.138".

This is suspiciously close to the 95% velocity propagation of parallel
line.
My question is, for a given coax with 66% velocity propagation, is the
formula 66% of 492 (325/f) or
66% of 468 (309/f)?

Thanks in advance