Butternut advertises a multiband (40,20,15,10) resonant radial system
(model STK) for use with their verticals. It is made from twinlead,
with notches in it.

See http://www.bencher.com/pdfs/00361ZZV.pdf

How does this work? Is there design information available anywhere so
one could build their own system for other bands?
How does its performance compare with normal radials?
Bandwidth, efficiency etc.

Bob W8ERD

On Wed, 01 Apr 2009 11:28:06 -0400, Bob Dixon wrote:

How does this work?

Hi Bob,

Pretty much in the fashion of regular radials.

Is there design information available anywhere so
one could build their own system for other bands?

Start with the nominal quarterwave length. Put it in the expected
environment. Measure SWR. Trim or lengthen as appropriate.

How does its performance compare with normal radials?

Normal being? Compared to 120 quarterwave radials?

Bandwidth, efficiency etc.

Oh! Bandwidth: probably wider.

Efficiency: probably much less.

Bandwidth and efficiency for ONE radial (or two, or three, or four...)
in this circumstance is normally in an inverse relationship when close
to the ground.

73's
Richard Clark, KB7QHC

I was referring to the tuned twinlead system shown in figure 6 of the
original reference http://www.bencher.com/pdfs/00361ZZV.pdf
How are the lengths determined (obviously not a quarter wavelength)?

Bob W8ERD



In article ,
Richard Clark wrote:

On Wed, 01 Apr 2009 11:28:06 -0400, Bob Dixon wrote:

How does this work?

Hi Bob,

Pretty much in the fashion of regular radials.

Is there design information available anywhere so
one could build their own system for other bands?

Start with the nominal quarterwave length. Put it in the expected
environment. Measure SWR. Trim or lengthen as appropriate.

How does its performance compare with normal radials?

Normal being? Compared to 120 quarterwave radials?

Bandwidth, efficiency etc.

Oh! Bandwidth: probably wider.

Efficiency: probably much less.

Bandwidth and efficiency for ONE radial (or two, or three, or four...)
in this circumstance is normally in an inverse relationship when close
to the ground.

73's
Richard Clark, KB7QHC

On Thu, 02 Apr 2009 09:37:06 -0400, Bob Dixon wrote:

I was referring to the tuned twinlead system shown in figure 6 of the
original reference http://www.bencher.com/pdfs/00361ZZV.pdf
How are the lengths determined (obviously not a quarter wavelength)?

Hi Bob,

Obviously not? Of course it is for at least 40M (overall length); and
of course it is for at least 10M (to the first notch); and half a wave
for 15M and half a wave 20M. Half waves are two quarters....

Those dimensions are the intent of tuned radials. Tuned radials have
some integer relationship to a quarter wave. Some commercial designs
might offer radial reactance (non-quarterwave relationship) to balance
out the inverse reactance seen in the vertical, but I don't think we
see it here.

Proximity to earth will change all of this, however. Layout a longer,
overall length without cutting the notches and tune for the lowest
band. Use that last 3 foot section to do this (like making it 6 feet
long at first). I would then work on the first notch for 20M and cut
it out long too (the 3'10" section is redundant and thus expendable)
so you can shorten towards the base. Then I would work on the second
notch, but cut closer to the base (say, at 18' from the base) and trim
towards the end to tune in 15M.

The same thing (compactness) could have as easily be arrived at by
using in dependant wires, all cut to quarter/halfwave and bundled
together. There is nothing particularly remarkable about the twinlead
in its own right except for mechanical stability.

73's
Richard Clark, KB7QHC

The same thing (compactness) could have as easily be arrived at by
using in dependant wires, all cut to quarter/halfwave and bundled
together.

First, since I am new to this ng, let me say hi to all.

Now the good stuff. I have always wondered this, but
like a multi band dipole, the reactance would lead the power to the
radials that are reasonant, and make the unreasonant radials invisible?
Would they have to be spaced apart, or could they be 'bundled'
(but not touching)...
I ask because I was thinking of making a 20/15/10M ground plane out of
an old copy of Ham Radio Anthology from 2003. They only have one radial
for 20 and 15, two for ten. And I was wondering why not just
piggy-back reasonant wires for all the bands..You may have answered
my question.

Sorry to interupt, but thanks for the info!

Tim
WN8OAB

On Thu, 02 Apr 2009 13:58:05 -0400, Tim wrote:

The same thing (compactness) could have as easily be arrived at by
using in dependant wires, all cut to quarter/halfwave and bundled
together.

First, since I am new to this ng, let me say hi to all.

Now the good stuff. I have always wondered this, but
like a multi band dipole, the reactance would lead the power to the
radials that are reasonant, and make the unreasonant radials invisible?
Would they have to be spaced apart, or could they be 'bundled'
(but not touching)...
I ask because I was thinking of making a 20/15/10M ground plane out of
an old copy of Ham Radio Anthology from 2003. They only have one radial
for 20 and 15, two for ten. And I was wondering why not just
piggy-back reasonant wires for all the bands..You may have answered
my question.

Sorry to interupt, but thanks for the info!

Tim
WN8OAB

Hi Tim,

Welcome to the free-for-all called newsgroups.

Wires that are adjacent are invisible in one sense, and fully visible
in another, and partially visible on the third hand.

Resonance is not, in an of itself, a condition that denotes
visibility, or even radiation. Resonance (or the lack of resonance)
is merely a characteristic - one of many.

Resonance in an antenna generally means the lack of reactance.
Reactance brings us back to adjacent wires. If a wire is resonant,
and another wire is brought into proximity, that second wire will add
some form of reactance and shift the resonant characteristic of the
first wire. Hence, if that second wire lacks mechanical integrity, it
will add/subtract reactance as the wind blows - not a pretty prospect.
This is benefit that is brought to the Butternut by using twinlead. I
would point out that this benefit would be quickly lost if they need
two twinleads to support more bands.

The Butternut radial design is simply a variation in the fan dipole
where several wires are connected at one point, but each wire
resonates in a different band. When constructing a fan dipole, the
general advice is to maintain some distance between the wires to
reduce interaction (the addition/subtraction of reactance to
neighboring wires). This separation is not herculean, six inches to a
foot is often quoted, and reports tend to emphasize the distant ends
being that far apart, with the ends at the common point being "fanned
out" to them (hence the term fan dipole).

The practicality of construction is found in the separation of the
wire. The twinlead construction is going to be the most difficult
(but not impossible, obviously), whereas wire that is radically
separated will have minimal interaction (aka invisible).

73's
Richard Clark, KB7QHC