Hello Jim:

Yeah 18 feet seems top work well in a mobile installation. Why is that?

Is it because the antenna puts RF Energy on the coax outer shield due to
a lack of ground surface. In all my antennas installs it seems that way.

So 18 feet of coax is roughly 3/4 of a wavelength, ( with a velocity
factory of .66) and any RF Energy coming back will have to come back
thru another 3/4 wavelength of coax.

Maybe that length vs wavelength is the best to use. Your comments....

Jay in the Mojave


jim wrote:
Feed length 'does' make a difference
when calculating swr