Cecil Moore wrote:
Tom Donaly wrote:
Many people over the years have done just fine loading their antennas
with lumped inductors.

That's not the point of this discussion, Tom. The
only question that needs to be answered here is:
Can a 2" dia, 100 T, 10" long loading coil have
a delay of 3 nS through it at 4 MHz? Do you support
such a technical absurdity? The Corum IEEE white
paper suggests that delay is in error by a magnitude.

All of the boundary test conditions given in Corum's
IEEE white paper are satisfied by a 75m bugcatcher
loading coil. There is no reason to believe that
the underlying principles of physics do not apply.
In fact, the diagram of the 1/4WL resonant system
looks exactly like a base loading coil, stinger,
and top hat as is used for 75m mobile operation.

Do you really believe that an antenna + loading coil has
to be a quarter wave long to resonate?
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
Do you really believe that an antenna + loading coil has
to be a quarter wave long to resonate?

Note: I am NOT talking about *physical* lengths.
The phase shift from feedpoint to tip has to be
*electrically 90 degrees* so the answer is yes.
For a base-loaded mobile antenna, the sum of the
phase shifts a

PS1. The phase shift through the loading coil.
PS2. The phase shift at the coil to stinger junction.
PS3. The phase shift in the stinger.

PS1 + PS2 + PS3 = 90 degrees.

In a typical 75m base-loaded mobile antenna, PS1
may be about 40 degrees, PS2 about 40 degrees, and
PS3 about 10 degrees.

PS2 is a freebie lossless phase shift compliments of
Mother Nature caused by the impedance discontinuity
between the coil and the stinger. If that phase shift
can be maximized, it should add to antenna efficiency.
--
73, Cecil http://www.w5dxp.com

Cecil Moore wrote:
Tom Donaly wrote:
Do you really believe that an antenna + loading coil has
to be a quarter wave long to resonate?

Note: I am NOT talking about *physical* lengths.
The phase shift from feedpoint to tip has to be
*electrically 90 degrees* so the answer is yes.
For a base-loaded mobile antenna, the sum of the
phase shifts a

PS1. The phase shift through the loading coil.
PS2. The phase shift at the coil to stinger junction.
PS3. The phase shift in the stinger.

PS1 + PS2 + PS3 = 90 degrees.

In a typical 75m base-loaded mobile antenna, PS1
may be about 40 degrees, PS2 about 40 degrees, and
PS3 about 10 degrees.

PS2 is a freebie lossless phase shift compliments of
Mother Nature caused by the impedance discontinuity
between the coil and the stinger. If that phase shift
can be maximized, it should add to antenna efficiency.

So, since the phase shift has to be 90 degrees, the antenna
should always resonate at the same frequencies a quarter wave
stub of the same electrical length would resonate at, right?
73,
Tom Donaly, KA6RUH

Tom Donaly wrote:
So, since the phase shift has to be 90 degrees, the antenna
should always resonate at the same frequencies a quarter wave
stub of the same electrical length would resonate at, right?

Not sure what you mean by this statement. 90 degrees
is 90 degrees. A mobile antenna physically shorter
than 1/4WL is still close to 90 degrees long at
resonance. (It is not exactly 90 degrees because of
the well-known end effects.)

In order for the reflected wave to be in phase with
the forward wave at the feedpoint (purely resistive
feedpoint impedance), the reflected wave must traverse
180 *electrical degrees* during its round trip. That
fact inticates that the antenna is electrically 90
degrees long.
--
73, Cecil http://www.w5dxp.com