Ian White, G3SEK wrote:
Think what would have happened if you had measured the impedance at the
TX end of your o/c transmission line (very high or very low, depending
on the length) and replaced it with a resistor and inductor/capacitor
giving the same value of R +/- jX.

There's no transmission line, so no traveling waves of anything, and no
reflections - just a transmitter with a very wrong value of load
impedance. The 1625s would have burned up just the same.

Yes, 1625's are pretty dumb but hopefully, we are smarter than the 1625's.
Here's more from the IEEE dictionary.

"resistance - (A) That physical property of an element, DEVICE, ...
(B) The real part of impedance. Note: Definitions (A) and (B) are
not equivalent ..."

"resistor - A DEVICE the primary purpose of which is to introduce
resistance into an electric circuit."

"impedance - (B) The ratio of the ... voltage ... to the ...
current ... (C) A physical DEVICE or combination of DEVICES ...
Definition (C) is a second use of 'impedance' and is independent
of definitions (A) and (B)."

"impedor - A DEVICE, the purpose of which is to introduce impedance
into an electric circuit."

In your above example, you changed the circuit from a (B) impedance to
an impedor. Even if the 1625's can't tell the difference, W5DXP can. :-)
Note that I, not the IEEE, capitalized 'DEVICE' in the above definitions.
--
73, Cecil http://www.qsl.net/w5dxp



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Uh, Reg, Voltaire wrote "Candide".
Perhaps you were thinking of Volta, the Italian.
And you forgot Maxwell, Cavendish and Faraday.
All brits, all important to this stew.
Plus a host of others all the way back to Greece and before.
And if more here had gotten as far as Gibbs, we could just write down the
DE's and the BC's and be done in a few lines of math.
But it has been virtually entertaining, don't you think?
73 es gud dx om
H.
NQ5H

ascii limited notation
------------------------
div D = rho (rho is
charge)
curl H - (partial with respect to time) D = J (J is current)
curl E + (partial with respect to time) B = 0
div B = 0

D = epsilon(naught) E
B = mu(naught) H



"Reg Edwards" wrote in message
...

The haggling, for years, about congugate matching, SWR, forward &
reflected
power, silly virtuallty, etc, has gone on long enough.

Only G3SEK, amongst the small minority of the radio population who
contribute to these walls, has a grasp of what it's all about. There are
obviously others who are too busy to waste their time on newsgroups.

But who am I to judge?

INTERNAL IMPEDANCE OF RF POWER AMPLIFIERS

Programs TRIODE1 and TETRODE1 assist with the classical design of tube
(valve) power amplifiers. They are very closely related to each other. A
key
design feature, the cathode current operating angle, is an input
parameter.

Apart from the drive and input-circuits, they also apply to their lower
power transistor equivalents.

For the benefit of those who may insist on knowing, these two programs are
based on the clssical theoretical analysis by americans Everitt, 1932 (who
was probably not original at that relatively late stage of the thermionic
tube). He was followed by Terman in a more practical but more uncertain
manner in the 1940's. No doubt there have been others. None of them, aware
of their weaknesses, would have wished to be worshipped as little tin
Gods.

The basics havn't changed since Ohm, Ampere, Voltaire and Heaviside.

Anyone responding to an enquirer, who feels in need of extra support in
his
reply, who refers back to the ancients merely displays his inability to
provide a logical explanation and a lack of underlying understanding.
There's nothing wrong, of course, in a lack of understanding except in
propagating it. (Most enquirers do not have the ancient books or easy
access
to the books anyway)

Neither of this pair of programs require a congugate match between
internal
impedance and the load. There's nothing magical about 50 ohms. It could be
any value as any appropriately designed SWR meter will assume. I have a
75-ohm model. All is based on assumptions. The only absolute value is SWR
itself which does not depend on Zo or Z load but merely on their ratio.

The only way to determine dynamic internal impedance of a PA is to
calculate
it AFTER THE AMPLIFIER HAS BEEN COMPLETELY DESIGNED. It is then too late
to
have any effect on design.

Just to satisfy curiosity the dynamic internal resistance of an amplifier
is
a calculated output quantity of program TETRODE1. It is of course of no
practical value. In the program it is referred to as the Source Resistance
when looking back into the 50-ohm output socket.
----
=======================
Regards from Reg, G4FGQ
For Free Radio Design Software
go to http://www.g4fgq.com
=======================

Hey, that's cool. Been a ham for 46 years, made it through Air Force
technical school, got a BSEE degree, and spent over 30 years doing
circuit design without ever once coming across the term "impedor". And
there it was, right in the IEEE dictionary. This newsgroup is sure
educational!

Roy Lewallen, W7EL

W5DXP wrote:
. . .

"impedor - A DEVICE, the purpose of which is to introduce impedance
into an electric circuit."

In your above example, you changed the circuit from a (B) impedance to
an impedor. Even if the 1625's can't tell the difference, W5DXP can. :-)
Note that I, not the IEEE, capitalized 'DEVICE' in the above definitions.

H. wrote,

Uh, Reg, Voltaire wrote "Candide".
Perhaps you were thinking of Volta, the Italian.
And you forgot Maxwell, Cavendish and Faraday.
All brits, all important to this stew.
Plus a host of others all the way back to Greece and before.
And if more here had gotten as far as Gibbs, we could just write down the
DE's and the BC's and be done in a few lines of math.
But it has been virtually entertaining, don't you think?
73 es gud dx om
H.
NQ5H


Reg likes to intentionally put things like that into his posts to
put us all on. If you read much Thackery, who made a good
living at one time writing about English con artists, you'll know
it's a part of the British national character.
73,
Tom Donaly, KA6RUH

Dave Shrader wrote:
How does the wrong load impedance comes into existence?
Is it not caused by the mismatch?

Yep, the mismatch causes reflected waves which, in turn, cause the wrong
load impedance. It's easy to see in the following thought experiment.

200W source---one second long 50 ohm lossless feedline-----open

The source will output 100V at 2A for two seconds from key down and
be perfectly happy. The "wrong" impedance arrives exactly with the
reflected wave after two seconds. The center of the steady-state SWR
circle is the "right" impedance and therefore will not exist after two
seconds.
--
73, Cecil http://www.qsl.net/w5dxp



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Roy Lewallen wrote:
Hey, that's cool. Been a ham for 46 years, made it through Air Force
technical school, got a BSEE degree, and spent over 30 years doing
circuit design without ever once coming across the term "impedor". And
there it was, right in the IEEE dictionary. This newsgroup is sure
educational!

So what are you going to do with your new found knowledge? :-)
--
73, Cecil http://www.qsl.net/w5dxp



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(Art Unwin KB9MZ) wrote in message om...


Slick

Dr Slick,
Way back in this thread you alluded to antennas as being
transformers. The more I think about that statement the more I see
it as being fact. Anything that involved coupling which all
antennas do can be drawn as a transformer !
Since the thread migrated all over the place did you feel that
the group agreed with that position?
Regards
Art


Some have emailed me personally, and we have pretty much agreed on
these two points(even Roy agreed with these, if you read his posts
here):


1. Two antennas (also called transducers) placed close together
actually can be considered a transformer, albeit a very inefficient
one.

So an antenna can be considered 1/2 of a full transformer, so i wasn't
that far off from a semantics point of view.


2. An antennas input impedance will depend on the impedance or
permeability of the medium it is radiating into. In other words, an
antennas free space input inpedance will be different from the input
impedance of the same antenna immersed in water.

This is of course with a completely water-proofed antenna.




I went on to point out that a toroid transformer of a specific
turns ratio, wire gauge, and core geometry, will definitely depend on
the permeability (impedance) of the core material for it's
characteristics.


Alas, i'm just a lowly practical engineer and not a PhD in EM
wave-propogation (obviously no one else here is either). But if a
transformer depends on 2 transducers' abilities to turn V and I into E
and H (and vice versa), and that this depends on the impedance of the
medium between them....then to me, an antenna is in some way
"matching" to the impedance of free space, 377 Ohms, even if the
energy has been converted to a different form.



Slick

Yeah, but it gave me a chance to mouth off.
And then I forgot Ben Franklin!
Anybody who'll fly a kite in a thunderstorm deserves mention.
I visited Cambridge once; Newton to Hawking,
Reg is in good company.
73
H.

"Tdonaly" wrote in message
...
H. wrote,

Uh, Reg, Voltaire wrote "Candide".
Perhaps you were thinking of Volta, the Italian.
And you forgot Maxwell, Cavendish and Faraday.
All brits, all important to this stew.
Plus a host of others all the way back to Greece and before.
And if more here had gotten as far as Gibbs, we could just write down the
DE's and the BC's and be done in a few lines of math.
But it has been virtually entertaining, don't you think?
73 es gud dx om
H.
NQ5H


Reg likes to intentionally put things like that into his posts to
put us all on. If you read much Thackery, who made a good
living at one time writing about English con artists, you'll know
it's a part of the British national character.
73,
Tom Donaly, KA6RUH

I wrote,

Reg likes to intentionally put things like that into his posts to
put us all on. If you read much Thackery, who made a good
living at one time writing about English con artists, you'll know
it's a part of the British national character.
73,
Tom Donaly, KA6RUH


I misspelled "Thackeray." I expect he'll forgive me, though.
73,
Tom Donaly, KA6RUH

W5DXP wrote:

William E. Sabin wrote:

If the transmission line input impedance is replaced with a lumped LCR
circuit, then confusion disappears and we have a conventional problem
in AC circuit analysis.


Some confusion disappears. Some additional confusion arises. It should
be recognized that replacing a V/I impedance with an impedor is a shortcut
and doesn't necessarily represent reality. Math models certainly do not
control reality. For instance, ghosting is not the same in the two cases.
A TDR will not give the same results.

I give up.

Bill W0IYH