On Thu, 02 Apr 2009 17:02:49 -0800, Richard Clark
wrote:

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.

The Butternut twinlead appears to be connected at each end, forming a
single wire folded back on itself. Is that the same as a fan dipole?

bob
k5qwg

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