On Sat, 12 Nov 2005 23:31:27 GMT, Cecil Moore wrote:

Dave Platt wrote:

Cecil Moore wrote:
Is it better than just feeding it with about 15 inches of ladder-line?

If I were going to feed a 5/4 with ladder line, for tower
side-mounting, I suppose I'd probably put the ladder line inside the
PVC support arm, and then connect it to some 50-ohm coax which was
wound around the outside of the arm to create a choke balun.

Cebik's stuff is probably for HF. EZNEC sez an 8 foot long, one
inch diameter dipole at 36 ft. height has a feedpoint impedance
of 86-j91 on 146 MHz. Heck, that's already better than some rubber
duckies. All it takes to resonate that impedance to a 50 ohm SWR
of about 1.6:1 is about 2.5 inches of 450 ohm ladder-line in
series. What could possibly be simpler than that?

With EDZ or it's evil twin in the other plane the 5/8 wave the
electrical length affects feed point R while the X is fairly large.
So you use some form of matching magic to transform that
unrulely X to R and thereby a match to a 50 ohm source and line.

If you looked at the Cebik article you will see how and why
plus it's result at 2m. I scaled his work for 6m and it worked
to the the decimal point.

Allison
KB1GMX