On Mon, 5 Apr 2010 06:27:54 -0700 (PDT), Cecil Moore
wrote:

On Apr 4, 4:19*pm, Bob wrote:
I'm plugging the velocity factor figure into Cecil's program for
optimum feedline lengths on a multiband dipole, IMAXMIN.EXE. Given the
approximate nature of this kind of feed, a ballpark figure is probably
okay.

Yes, given all the variables, adjusting the final length, sometimes by
a few feet (depending on wavelength) is almost always required to
achieve system resonance. Remember that this approach is designed to
eliminate the tuner and therefore eliminate tuner losses and it is
designed to be used with a 1:1 current-choke-balun. Owen's comments
are certainly valid for systems using antenna tuners and 4:1 baluns.
In fact, if one chooses a ladder-line length halfway in between my
"good" (current maximum) and "bad" (voltage maximum) lengths, one will
obtain the odd 1/8 wavelengths points that are recommended for use
with 4:1 baluns.

The more I look at it, the odd 1/8 wavelengths is probably the way I
will go, connecting to my tuner's 4:1 balun. There will be a 130 foot
flat-top, and the 450-ohm feedline length can be somewhere between 50
to 100 feet or so. Tnx for the input!

Bob
k5qwg

Those points result in a ballpark impedance in the
neighborhood of Z0 +/- jZ0/4, e.g. 400+j100 ohms. For those who
understand a Smith Chart, a picture is worth a thousand words.

http://www.w5dxp.com/smith.htm