On Mar 24, 11:57*am, "Richard Fry" wrote:
Radiation resistance is a function of the end-end length of the helix and
the frequency, whether the helix is self-resonant or not.

Yes, I thought that was the purpose of your posting. As Kraus said,
the helical has an advantage over a short straight conductor - same
radiation resistance with less reactance. The radiation resistance of
a 6" long Texas Bugcatcher coil is approximately the same as a 6"
piece of wire.
--
73, Cecil, w5dxp.com

Cecil Moore wrote:
... The radiation resistance of a 6" long Texas Bugcatcher coil
is approximately the same as a 6" piece of wire.
______________

We agree on that point, Cecil.

But if, as if you posted earlier, "a helical monopole is 90 degrees long at
the design frequency," are you claiming that such a short, self-resonant,
normal-mode, helical monopole has the same radiation resistance and system
performance as a self-resonant linear monopole of about 1/4 of a free-space
wavelength (other things equal)?

And if you do, could you please explain why this approach was not adopted
many decades ago for use by AM broadcast stations?

On Mar 24, 5:35*pm, "Richard Fry" wrote:
But if, as if you posted earlier, "a helical monopole is 90 degrees long at
the design frequency," are you claiming that such a short, self-resonant,
normal-mode, helical monopole has the same radiation resistance and system
performance as a self-resonant linear monopole of about 1/4 of a free-space
wavelength (other things equal)?

Absolutely not. I am claiming that a 1/8WL long *resonant* helical is
electrically 90 degrees long and has approximately the same radiation
resistance as a 1/8WL straight piece of wire. Radiation resistance and
linear *physical* length are correlated. Radiation resistance and
*electrical* length are NOT correlated. As I said previously
(concerning standing wave antennas) the feedpoint impedance is
associated with the electrical length of the antenna. Radiation is
associated with the physical length of the antenna.
--
73, Cecil, w5dxp.com

On Fri, 25 Mar 2011 04:36:26 -0700 (PDT), Cecil Moore
wrote:

On Mar 24, 5:35*pm, "Richard Fry" wrote:
But if, as if you posted earlier, "a helical monopole is 90 degrees long at
the design frequency," are you claiming that such a short, self-resonant,
normal-mode, helical monopole has the same radiation resistance and system
performance as a self-resonant linear monopole of about 1/4 of a free-space
wavelength (other things equal)?

Absolutely not. I am claiming that a 1/8WL long *resonant* helical is
electrically 90 degrees long and has approximately the same radiation
resistance as a 1/8WL straight piece of wire. Radiation resistance and
linear *physical* length are correlated. Radiation resistance and
*electrical* length are NOT correlated. As I said previously
(concerning standing wave antennas) the feedpoint impedance is
associated with the electrical length of the antenna. Radiation is
associated with the physical length of the antenna.

Cecil,
You frequently embed comments in your posts that I find especially
important to antenna basics.

I am starting a list of Antenna Axioms with this:

"Radiation resistance and linear *physical* length are correlated.
Radiation resistance and *electrical* length are NOT correlated. As I
said previously (concerning standing wave antennas) the feedpoint
impedance is associated with the electrical length of the antenna.
Radiation is associated with the physical length of the antenna.
--
73, Cecil, w5dxp.com"

As a student of antennas I do appreciate your stating the basic
principals in answering questions.

There are a lot of Hams who still think a short resonate dipole is
just as good as a full size dipole.

On Mar 25, 9:53*am, John Ferrell wrote:
There are a lot of Hams who still think a short resonate dipole is
just as good as a full size dipole.

That would be true if everything was lossless. Unfortunately in the
real world, a short dipole *system* almost always suffers more overall
losses than a well-designed full size dipole *system*. In general, the
shorter the dipole, the greater are the losses in the process of
transferring energy from the source to the load. Short dipoles are
indeed efficient radiators of the *energy delivered to the antenna*.
The loss problems are in the energy transfer/delivery systems, not in
the energy radiating system.

The reason that a high-Q center loading coil system has less loss than
a 100% helical system is interesting. The impedance discontinuity at
the loading-coil/whip junction yields a lossless phase shift that
contributes to the electrical length of the antenna. It is a rare
"something-for-nothing" gift from the Antenna Gods.
--
73, Cecil, w5dxp.com