On Tue, 9 Dec 2008 23:11:10 +0100, "Fred PA0FVH"
wrote:

Dear group,

As a temporarily solution I would like to use a cheap 5/8, 6/8 or 7/8 WL
commercially available CB antenna as a non resonant vertical with elevated
radials for use on 10 - 40 meters tuned by an automatic remote ATU at the
base of the antenna. I used MMANA and EZNEC (demo) to calculate the expected
impedance for the frequency range and found too many results for the height
of the antenna. Now I am confused about what to select.
Is 5/8WL on 10meters a good height or 8 meter (22')?
What I want is a low take off angle on 20 and 30 meters with high efficiency
and an impedance which my remote ATU can handle.

Hi Fred,

6/8th and 7/8th wavelength at 10M would not have the best low angle
charateristic. At the longer wavelengths it should get progressively
better (as you may tell from EZNEC demo).

7/8th wavelength at 10M may also be hard to match with your ATU, but
worth a try.

Shorter antennas for longer wavelengths may find more loss in the ATU
than you would care to have, but a 5/8ths at 10M might be the best
work-around; and the shortest you should go.

73's
Richard Clark, KB7QHC

Hi Guys,

Thanks for your good suggestions.

The first thing to understand is that for the most part the CB 5/8, 6/8,
7/8
antennas have nothing to do with the actual height. Manufacturers started
claiming these lengths because the CBers believe(d) longer is better

The physical length of those antennas available over here are 6.5m, 9.1m and
9.5m. So any height between 6.5m and 9.5m would be possible.
It is an alternative for going to a DIY store to get aluminum tubing.

The other problem is if the reactive component gets too far for your
tuner to handle, but without knowing the tuning range of your tuner,
that's hard to know.

My remote ATU (Pi matching) has an inductance range from 0 to 63uH and the
capacitance ranges from 0 to 6300pF

Fred, PA0FVH

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