On Apr 8, 1:13*am, Richard Clark wrote:
On Wed, 7 Apr 2010 20:09:56 -0700 (PDT), Tom Horne
wrote:

I am interested in having a rapid set up multi-band vertical for Field
Day and EMCOMM. *If I use the Hy-Gain sixty four foot (64') push up
mast as the radiator and an ICOM AH-4 as the automatic antenna tuner
is this likely to be an effective approach to having a rapid set up
multi band vertical? *

Hi Tom,

Yes.

Will I need radials? *

Yes.

Should they be elevated or
can they lie on the ground? *

Yes.

Since the total length of the radiator is
less than a 1/4 wave on eighty meters at say 3.6 MHz will that make
the antenna ineffective on eighty meters?

No.



Second question
5th, actually.
would four of those sixty four foot masts make an
effective forty meter four square.

Yes.

*Yes I realize that it would cost
eight hundred dollars for the masts alone before the cost of
controller, remote, phasing coax, and control cable. *Once again would
radials be required for forty meters.

Yes.

I've only been back in radio for a few years after very long gap so
I'm starting over and finding the learning curve a little steeper than
I remember.

You are still on the level wit the climb to come. *There are a LOT of
details to make those simple answers work.

73's
Richard Clark, KB7QHC

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?
--
Tom Horne, W3TDH

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?

You'll need to have some loads on the vertical also.

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?

That will be one interesting antenna.

Is there some reason that you are fixing on a vertical?

- 73 de Mike N3LI -

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

On Fri, 16 Apr 2010 10:19:40 -0700, Richard Clark
wrote:

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.

Somehow, that didn't come out right.

The number and length of radials is, of course, confined to the
discussion of a vertical antenna.

The number of variables in this relates to frequency, match,
efficiency, loss (which at first blush the last two "seem" to be about
the same thing), and (incorrectly) launch angle.

Another point that occurred to me: The notion of a tuned radial, and
it laying on the ground is an exercise in futility. The proximity of
ground is going to seriously detune the radial which will mock your
effort. Tuned radials are more a property of elevated verticals. Some
commercial verticals which come with tuned radials, or where you will
be expected to supply them, have a tacit expectation of your also
mounting the antenna some appreciable distance above ground.

73's
Richard Clark, KB7QHC