Roy Lewallen wrote:
What's the mystery? What's the big deal?

Intel has a lot of problems with buses running in the hundreds of MHz
because of the delay in the conductor path between chips. If I tell them
to install a coil in each path instead of a conductor, the delays will
disappear, right? You're pulling my leg, right?

At frequencies where the delay through a coil is a negligible part of
an AC cycle, the delay can be ignored. At frequencies where the delay
through a coil is not a negligible part of an AC cycle, the delay cannot
be ignored and circuit theory will not yield the correct answers. At the
point where the circuit theory error becomes too great, we must switch
to distributed network analysis.

Consider one foot of wire carrying a 1 GHz signal. The phase shift is
greater than 360 degrees. Can we reduce the phase shift to zero by
installing a coil over that one foot length? You *are* pulling my leg,
right?

All coils have delays. Sometimes those delays are negligible. Sometimes
they are not. The delay through a 75m mobile loading coil is NOT negligible.
That assumption causes errors. The phase delay through a coil is approximately
the same as the section of line replaced by the coil. For an 80m loading coil,
that delay is around 80 degrees or the equivalent of 57 feet of wire. Otherwise,
the forward and reflected currents on the antenna would not have the proper phase.
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:
Here's an experiment to try.
Take Cecil's model of the vertical with the loading coil. Add a single
horizontal wire, 10 feet long, connected at the top of the loading coil.
That is, make the new wire go from 0, 0, 26 to 10, 0, 26. Notice how
much current there is in the horizontal wire. Notice how much different
the current is in the vertical below the wire compared to above the
wire. Look familiar?

And please note that horizontal wire generates lots of horizontally
polarized radiation where there is none for the horizontal stub alone.
--
73, Cecil http://www.qsl.net/w5dxp



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Huh?

The stub produces just as much horizontally polarized radiation as the wire.

Run your stub vertical model with an elevation plot, and azimuth angle
of 90 degrees. Click FF Tab. Note the magnitude of the horizontal
component -- roughly -30 dBi. Then repeat with the experimental model
with the single horizontal wire.

As I mentioned in my lengthy posting, the radiation from the stub isn't
a large part of the overall field, and this certainly shows it. But it's
certainly enough to disturb the vertical's current. Exactly the same
thing holds for the straight wire. Common mode current is common mode
current. No magic, no mysterious phenomena "not accounted for" by EZNEC.

Roy Lewallen, W7EL

Cecil Moore wrote:

And please note that horizontal wire generates lots of horizontally
polarized radiation where there is none for the horizontal stub alone.

Watch this space for another thrilling episode of the long-running,
nerve-tingling mystery story "The Case of the Missing Third Wire".

Roy and Cecil -- I find your posts most informative -- ignore the flack.
Keep up the good work -- valuable sources

--
73 From The Keyboard
===============
"Roy Lewallen" wrote in message
...
I'm sorry. If I'm bothering the readers, I'll be glad to bow out.

My postings aren't really directed to Cecil -- I know much better than
to imagine that I'll ever change his mind, and I'm a firm believer in
not wasting time on things I can't change.

No, you and the other readers are really the audience, and the whole
reason for the postings. If you and the other readers would rather I
shut up, I'll be more than happy to spend my time at more productive
pursuits.

Just let me know.

Roy Lewallen, W7EL

David Robbins wrote:
Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Cecil Moore wrote:

Roy Lewallen wrote:

Roy Lewallen wrote:

The stub produces just as much horizontally polarized radiation as the
wire.

Not true. The wire produces 2 dB more radiation than the stub. Given
that the stub is located in a high current region compared to the wire,
it is significant how much the stub doesn't radiate. If you replace
the stub with an equal length of single wire, it radiates 4 dB more
than the stub.

Run your stub vertical model with an elevation plot, and azimuth angle
of 90 degrees. Click FF Tab. Note the magnitude of the horizontal
component -- roughly -30 dBi. Then repeat with the experimental model
with the single horizontal wire.

Thanks, Roy, that's an angle I had not looked at. Results are above.

As I mentioned in my lengthy posting, the radiation from the stub isn't
a large part of the overall field, and this certainly shows it. But it's
certainly enough to disturb the vertical's current. Exactly the same
thing holds for the straight wire. Common mode current is common mode
current. No magic, no mysterious phenomena "not accounted for" by EZNEC.

What EZNEC doesn't account for is the phase delay through a bugcatcher
coil which is an appreciable percentage of a wavelength. EZNEC is incapable
of modeling a bugcatcher coil. The only coil that EZNEC is capable of modeling
is one that does not and cannot exist in reality.

Therefo One cannot use EZNEC to try to prove the current is the
same at both ends of a bugcatcher coil which is what kicked off
this entire discussion.
--
73, Cecil http://www.qsl.net/w5dxp



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Reg Edwards wrote:
Watch this space for another thrilling episode of the long-running,
nerve-tingling mystery story "The Case of the Missing Third Wire".

Reg, you have a black box in the middle of a transmission line with
a high SWR. You measure the current into the box and current out of
the box. You measure 1 amp at 0 degrees going in and 1 amp at 180 degrees
going out. This means that both currents are flowing into the box at
the same time. There is no third wire. What's in the box?
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil, W5DXP wrote:
"What EZNEC doesn`t account for is the phase delay through the
bugcatcher coil which is an appreciable percentage of a wavelength."

It needs to have enough delay to replace that missing from the resonant
length of the antenna as ON4UN shows in his Fig 9-22.

Inductors are retardation coils.. They delay current change much as a
flywhell inhibits change in rotation. When voltage is applied to an RL
circuit, current is a function of time. If reactance in a circuit is
low, instantaneous current is almost in-phase with instantaneous applied
voltage. There is little if any delay of current in response to applied
voltage. If inductance in a circuit is high, delay of current is high.
Terman gives an example of inductive delay on page 643 of his 1955
edition:

"Another type of artificial line, suitable for low power operation,
consists of a coaxial cable in which the inner conductor is a continuous
coil of small wire wound on an insulating cylindrical core. This greatly
increases inductance per unit length of line with corresponding
reduction in velocity and increase in time delay per unit length. It is
possible with such a line to obtain a round-trip transit time of as much
as 1 microsecond in a length of two feet.

Best regards, Richard Harrison, KB5WZI

What's in the box?

Reg with whatever he is drinking :-)

Richard Harrison wrote:

Cecil, W5DXP wrote:
"What EZNEC doesn`t account for is the phase delay through the
bugcatcher coil which is an appreciable percentage of a wavelength."

It needs to have enough delay to replace that missing from the resonant
length of the antenna as ON4UN shows in his Fig 9-22.

This is true in order to get the feedpoint voltage and current in phase,
i.e. in order to resonate the antenna.

The voltage needs 180 degrees round trip delay from the feedpoint to
the end of the antenna and back.

The current needs 360 degrees round trip delay from the feedpoint to
the end of the antenna and back. 180 degrees of that comes from the
reversal of direction at the open end.

Can someone please measure the delay through a 75m bugcatcher coil?
I simply do not believe it is zero, i.e. faster than light.
--
73, Cecil http://www.qsl.net/w5dxp



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