On Tue, 3 Oct 2006 13:33:21 +0100, Ian White GM3SEK
wrote:

The missing part
is the velocity factor of the twin-lead when acting as a stub, which
means that the electrical length of the stub is different from the
physical length. Which of those two lengths would you use in the NEC
model?

Hi Ian,

This is simply a veiled expectation for EZNEC not being able to model
the "special attributes" of the antenna.

The answer is easy for a single-band model; but it's not so easy to
create one NEC model that will be valid for all the bands this antenna
is designed to cover.

The answer is even easier than that. The Lattin antenna has a basic
rationale behind it that does not demand two different lengths: stub
tuning which is an electrical quality (not physical). What acts like
a stub, acts like a stub for any wire mesh modeling a stub. The
Lattin antenna does not exhibit this action to any correlation to
frequencies attributed to it. It is THAT simple. Appeals to physical
size relate only to the far field radiation characteristic. Even here
the Lattin is noted for being un-notable.

You don't need to worry about velocity factor, or dielectrics when the
basic rationale calls it a stub and it doesn't work as a stub for bare
wire. The Franklin antenna employs some of the same geometries and
nowhere makes a desperate grab for theoretical underpinnings called
stubs. Yet the Franklin delivers as promised if or when you add
dielectrics. The Franklin's simple distribution of currents (which
works for every antenna) works without having stray wires tacked on
like Irish Pennants. There are more apologists for this design than
working Lattins flying their tuning wires (in their notorious
disregard for the rationale of the design).

The fact of the matter is that modeling lays bear the myth.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
You don't need to worry about velocity factor, or dielectrics when the
basic rationale calls it a stub and it doesn't work as a stub for bare
wire.

Consider a folded dipole made from Wireman #562. The radiating
part of the antenna has a VF of 0.95 and the feedline has a
VF of 0.8. Identical wires with 19% different VFs. How does
EZNEC handle that?
--
73, Cecil http://www.w5dxp.com

On Tue, 03 Oct 2006 17:14:00 GMT, Cecil Moore
wrote:
How does EZNEC handle that?
Try using the excellent online help manual.