Rick (W-A-one-R-K-T) wrote:
Since I am feeding with ladder line and a tuner, is there a particular
advantage to cutting the antenna as a half wavelength on 160, or would I
be just as well off to make it as long as I have space for without
considering its actual resonant frequency?

Fed with ladder-line, there is no particular advantage to
making the dipole 1/2WL long. If the feedpoint impedance
is 50 ohms, the SWR will be 9:1 on 450 ohm ladder-line.
The impedance seen by the tuner will be some transformed
impedance associated with that 9:1 SWR and can range up
to 4050 ohms if the feedline length is 1/4WL. I personally
like to feed a 75m 1/2WL dipole with 1/2WL of ladder-line
to duplicate the antenna feedpoint impedance at the tuner
but that results in an unwieldy ladder-line length of
233 feet on 160m.

In fact, one popular length for 160m is a 204 foot dipole
center-fed with 60-100 foot of ladder-line. With 60 feet
of ladder-line, it is known as the double-sized G5RV. With
60+ to 100 feet of ladder-line, the impedance seen by the
tuner on 160m is fairly low with some inductive reactance.

Another consideration for dipole length is the EDZ length
frequency. If you divide 1200 by the length of the dipole,
you will get the EDZ frequency in MHz. Above the EDZ
frequency, the radiation pattern breaks up into multiple
lobes with a smaller amount of broadside radiation. The
free demo version of EZNEC will predict the radiation
patterns.
--
73, Cecil http://www.w5dxp.com