On Thu, 15 Apr 2010 23:26:55 -0700 (PDT), Tom Horne
wrote:

Richard
Please share the rest of the story. If we lay out multi length
radials for the middle of each band, say four of them, and feed the
vertical with the auto tuner would we be able to make it work on
eighty, and forty? When we use a half wave end fed zep in the form of
a J pole on two meters we don't need a counterpoise. If I extend this
mast to a half wave on forty will I still need a counterpoise?

Hi Tom,

Thanx for something more specific that we can get our teeth into.

If you lay out radials that are tuned, such as you suggest, then you
wouldn't need an autotuner. There is, of course, the state of tune in
the radiator that needs to be accounted for, and I suppose the
autotuner would be put to work in that regard.

If so, then you are putting too much effort into the tune of the
radials. On the third hand, it doesn't hurt in the overall effort.

If you are going to have an autotuner (is this at the base of the
radiator, or back in the shack?); then there is a simpler and probably
more efficient use of the radial wire.

Over the years, the topic of how many and how long of radials with a
horizontal has had so many variables that the discussion ran to
examining the trivial instead of being useful. The useful advice is
to lay down as many radials as you can, but with a couple to three
dozen being a comfortable upper limit instead of the classic 120.
Their length should be equal to the radiator's height.

This doesn't make for a "tuned" vertical (except, perhaps, on some
frequency that probably is not in a Ham band if the height of the
antenna is ad-hoc); but it will be as efficient as is practicable. You
will still have to tune it. You will still suffer transmission line
loss related to the SWR exhibited at the feedpoint. It can be
unmanageable if its dimension approaches half-wave. Some of these
negatives can be managed by tuning the feedpoint with matching and
this is why I asked where the autotuner was located.

You anticipate the half-wave in your last question. The classical
answer there is no, you won't need a standard ground treatment. But
if you don't have some thing there, then tuning may become a chore
because the radiator, whatever its length, is always HALF of the
system. The radials typically are thought of as the other half. If
you don't have any, your transmission line will take up that function
in one way or another, and often to your annoyance.

As for the JPole discussion. Many who crow about their being simple
tunes and there being no problems with matching, some are simply
experiencing the transmission line being brought both into the tune
and the radiation. The second part of that equation lengthens the
overall radiator and sends the signal skyward. Yes, it tuned up fine,
but you then have a deaf antenna - suitable for the local repeater,
but so is an elevated rubber ducky.

73's
Richard Clark, KB7QHC