Loading Coils; was : Vincent antenna
 

On Dec 7, 3:02 pm, wrote:
On Dec 7, 1:00 pm, Cecil Moore wrote:





Keith Dysart wrote:
If the 100 ohm line was only 5 degrees long, how
long would the 600 ohm line have to be to obtain
0 ohms at the input?

-jcot(5) = -j11.43 normalized to Z0=100 ohms

-j100(11.43) = -j1143 ohms at the junction

-j1143/600 = -j1.905 normalized to Z0=600 ohms

arctan(1.905) = 62.3 degrees of Z0=600 ohm line

Would the phase shift at the junction still be
36.6 degrees?

The new phase shift would be 90-5-62.3 = 22.7 deg.

62.3 + 5 + 22.7 = 90 degrees

This example would correspond to a larger coil and
a shorter stinger in a loaded mobile antenna.
--
73, Cecil http://www.w5dxp.com

The smith chart shows this well. If I go up only 5 degrees on the
outer circle of open-end (infinite impedance on the 100 ohm line),
lower values of electrical angle corresponds to higher reactance, in
this case -j1143 for the 5 degree line instead of -j567 for the 10
degree line at the junction. The new phase shift at the junction
should be, and is, now lower since the 100 ohm line has a higher
capacitive reactance at the junction. As the 100 ohm line is shortened
to 0 degrees, we have a 600 ohm transmission line that is open and now
the 600 ohm line must be lengthened to the full 90 degrees for 1/4W.
This would correspond to a coil with no stinger.- Hide quoted text -

- Show quoted text -

Ooops, I am posting from the web. This is AI4QJ.

Loading Coils; was : Vincent antenna
 

On Dec 7, 1:00 pm, Cecil Moore wrote:
Keith Dysart wrote:
If the 100 ohm line was only 5 degrees long, how
long would the 600 ohm line have to be to obtain
0 ohms at the input?

-jcot(5) = -j11.43 normalized to Z0=100 ohms

-j100(11.43) = -j1143 ohms at the junction

-j1143/600 = -j1.905 normalized to Z0=600 ohms

arctan(1.905) = 62.3 degrees of Z0=600 ohm line

Would the phase shift at the junction still be
36.6 degrees?

The new phase shift would be 90-5-62.3 = 22.7 deg.

62.3 + 5 + 22.7 = 90 degrees

So sometimes a 600 to 100 ohm discontinuity
produces a 36.6 degree phase shift and sometimes
it produces a 22.7 degree phase shift (and probably
any value in between).

I suggest that "work[ing] up the phasor diagrams of
the component voltages (or currents) at the junction
where rho = (600-100)/(600+100) = 0.7143" will
not be useful for predicting the phase shift.

....Keith

Loading Coils; was : Vincent antenna
 

On Dec 7, 12:46 pm, Cecil Moore wrote:
Keith Dysart wrote:
You have done this before; postulating
explanations that only work in the complexity
of the "real" world, but fail when presented with
the simplicity of ideal test cases.

For Pete's sake, Keith, Ohm's law doesn't even
work when R=0.

A rather large red herring. Ideal components are
the topic, and we mostly use ideal wire with R=0
without difficulty.

Then, when the explanations fail on the simple
cases, claiming these cases are not of interest
because the real world is more complex.

I define the boundary conditions within which my
ideas work. Whether they work outside those defined
conditions is irrelevant. I believe they do work
for ideal conditions, but I don't have the need
to prove a "theory of everything".

Sounds good, but mostly you do not examine
ideal conditions because they tend to show that
the models fail. With non-ideal conditions, the
discussion is easy to drive far from the target
and prevent resolution of whether the model
works.

....Keith

Loading Coils; was : Vincent antenna
 

Tom Donaly wrote:
Mike Coslo wrote:
"Mike Kaliski" wrote in

I went along to a couple of meetings many years ago. Full of under
achievers with high IQ's complaining how they weren't being recognised
or credited in their exams/career/promotion ladder/etc.

Intelligence is like talent. It is a gift.

What you do with it is what is important. Just because you have one or
the other is almost irrelevant if you don't have the other tools
needed to be sucessful.

I feel like such a piker here - I'm only 150........


- 73 de Mike N3LI -

That's o.k. It just means you think less like Terman than some of the
others in this group do.


I was a little shocked to read his bio.

- 73 de Mike N3LI -

Loading Coils; was : Vincent antenna
 

Keith Dysart wrote:

Sounds good, but mostly you do not examine
ideal conditions because they tend to show that
the models fail. With non-ideal conditions, the
discussion is easy to drive far from the target
and prevent resolution of whether the model
works.

My postulate is that Newton was wrong: moving objects come to a rest
without any external applied force. Every observation made supports
this. There's no need to consider what happens in a frictionless
environment, since such a thing doesn't exist.

Roy Lewallen, W7EL

Loading Coils; was : Vincent antenna
 

On Dec 7, 3:05 pm, Keith Dysart wrote:
On Dec 7, 1:00 pm, Cecil Moore wrote:





Keith Dysart wrote:
If the 100 ohm line was only 5 degrees long, how
long would the 600 ohm line have to be to obtain
0 ohms at the input?

-jcot(5) = -j11.43 normalized to Z0=100 ohms

-j100(11.43) = -j1143 ohms at the junction

-j1143/600 = -j1.905 normalized to Z0=600 ohms

arctan(1.905) = 62.3 degrees of Z0=600 ohm line

Would the phase shift at the junction still be
36.6 degrees?

The new phase shift would be 90-5-62.3 = 22.7 deg.

62.3 + 5 + 22.7 = 90 degrees

So sometimes a 600 to 100 ohm discontinuity
produces a 36.6 degree phase shift and sometimes
it produces a 22.7 degree phase shift (and probably
any value in between).

That's right, depending on the electrical (and physical) length of the
100 ohm line, it will have different values of reactance as seen by
the 600 ohm line, therefore different phase shifts, all the way to
zero when the length of the 100 ohm line is 0 degrees and the
reactance is infinite (the 600 ohm line sees an open circuit). Say at
0+ degrees, -jX(C) = 1000000000; this is where you see it headed when
you look at the smith chart.

At zero degrees of 100 ohm line, you have 90-0-90 = 0 degrees at the
discontinuity.

AI4QJ

Loading Coils; was : Vincent antenna
 

Dave Heil wrote:
Mike Coslo wrote:
"Mike Kaliski" wrote in

I went along to a couple of meetings many years ago. Full of under
achievers with high IQ's complaining how they weren't being recognised
or credited in their exams/career/promotion ladder/etc.

Intelligence is like talent. It is a gift.

It can be more like a curse. There's nothing quite like a number of
teachers telling Junior's parents that Junior is gifted.

What you do with it is what is important. Just because you have one or
the other is almost irrelevant if you don't have the other tools
needed to be sucessful.

I feel like such a piker here - I'm only 150........

You don't look that old, Mike.

I would be younger, but I was sick a lot as a kid....

- 73 de Mike N3LI -

Loading Coils; was : Vincent antenna
 

Dave Heil wrote:
Mike Coslo wrote:
"Mike Kaliski" wrote in

I went along to a couple of meetings many years ago. Full of under
achievers with high IQ's complaining how they weren't being recognised
or credited in their exams/career/promotion ladder/etc.

Intelligence is like talent. It is a gift.

It can be more like a curse. There's nothing quite like a number of
teachers telling Junior's parents that Junior is gifted.


Little Mikey just doesn't apply himself.....

Little Mikey was bored, but that would mean it was their fault

Oops sorry about that - it was a thrid grade flashback 8^)


- 73 de Mike N3LI -

Loading Coils; was : Vincent antenna
 

wrote:
The smith chart shows this well.

Dan, I'm glad you understand. Now it is your turn
to get nibbled down to nothing by the guru gaggle
of geese.
--
73, Cecil http://www.w5dxp.com

Loading Coils; was : Vincent antenna
 

Cecil Moore wrote:
Dave Heil wrote:
Where's the fulfillment in standing around in a room full of folks
congratulating each other on how smart they are?

It gets the females turned on.

It is a well know scientific fact the only true aphrodisiac is a man
doing housework.

- 73 de Mike N3LI -