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Old February 26th 05, 09:34 AM
Rich Grise
 
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On Fri, 25 Feb 2005 22:35:28 -0600, Cecil Moore wrote:

Rich Grise wrote:
Evidently, the guy's never tuned up a 40 meter pi-net output transmitter. ;-)

If that's not impedance matching, I don't know what it is! (Oh, "Load line"
matching? What are the two parameters of the load line? Voltage and Current,
right? What's the slope of the load line? Impedance!)


And there's the catch. If the load line is the source
impedance, the load (not the designer) effects the source
impedance.


Apparently, I'm not following the same conversation here, because I
thought that the impedance matching network (in the instant example, the
pi-net output of the transmitter) was what translated the load impedance
to the source impedance, matching both in the process.

Thanks,
Rich


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Old February 26th 05, 09:36 AM
Rich Grise
 
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On Fri, 25 Feb 2005 21:42:37 -0800, Larry Brasfield wrote:

Uuugh. Mmmmph. Me drag woman to cave by hair.


Uh. Nuh. Drag _FROM_ hair.

  #53   Report Post  
Old February 26th 05, 01:20 PM
Airy R.Bean
 
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My "Bailey" amps (Wireless World c. 1970) have lots
of internal resistances, all soldered in neatly by hand.

In your comment below, I think that you have "output"
much "impudance".


"Reg Edwards" wrote in message
...
The phrase "output impedance" in connection with amplifiers is ambiguous

and
likely to result in arguments.
The correct description is "internal impedance" or "internal resistance"

and
should always be used.



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Old February 26th 05, 03:33 PM
Cecil Moore
 
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Rich Grise wrote:

On Fri, 25 Feb 2005 22:35:28 -0600, Cecil Moore wrote:

Rich Grise wrote:
If that's not impedance matching, I don't know what it is! (Oh, "Load line"
matching? What are the two parameters of the load line? Voltage and Current,
right? What's the slope of the load line? Impedance!)


And there's the catch. If the load line is the source
impedance, the load (not the designer) effects the source
impedance.


Apparently, I'm not following the same conversation here, because I
thought that the impedance matching network (in the instant example, the
pi-net output of the transmitter) was what translated the load impedance
to the source impedance, matching both in the process.


Maybe I inferred wrong. From your "load line equals
impedance" statement above, I inferred that you were
implying that the load line *is* the source impedance.
--
73, Cecil http://www.qsl.net/w5dxp


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Old February 26th 05, 04:51 PM
Allan Herriman
 
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On Sat, 26 Feb 2005 04:53:03 +0000 (UTC), "Reg Edwards"
wrote:

The phrase "output impedance" in connection with amplifiers is ambiguous and
likely to result in arguments.

The correct description is "internal impedance" or "internal resistance" and
should always be used.



S22 is fairly well defined.

Allan


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Old February 26th 05, 05:01 PM
Rich Grise
 
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On Sat, 26 Feb 2005 08:33:25 -0600, Cecil Moore wrote:

Rich Grise wrote:

On Fri, 25 Feb 2005 22:35:28 -0600, Cecil Moore wrote:

Rich Grise wrote:
If that's not impedance matching, I don't know what it is! (Oh, "Load line"
matching? What are the two parameters of the load line? Voltage and Current,
right? What's the slope of the load line? Impedance!)

And there's the catch. If the load line is the source
impedance, the load (not the designer) effects the source
impedance.


Apparently, I'm not following the same conversation here, because I
thought that the impedance matching network (in the instant example, the
pi-net output of the transmitter) was what translated the load impedance
to the source impedance, matching both in the process.


Maybe I inferred wrong. From your "load line equals
impedance" statement above, I inferred that you were
implying that the load line *is* the source impedance.


No, just trying to make the point that it does, in fact, _have_ an
impedance. (even if it's running class E.) What that exact impedance is,
of course, is left as an exercise for the reader. :-)

And another thing - in a transmitter, the impedance matching only happens
at the one frequency, which is a lot different scenario from, say, a
stereo. This could be a confusion factor here.

Thanks,
Rich


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Old February 26th 05, 07:00 PM
Richard Harrison
 
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John Woodgate wrote:
"The problem is that people say "output impedance" when they mean "load
impedance".

Quite right. I`ll use "source" and "load".

Current through a load depends on the voltage. Ratio of volts to amps is
the impedance. A source with the same resistance and offsetting
reactance to the load enjoys a Goldilocks relationship with its load.
The source`s volts and amps perfectly match the demands of the load.
It`s just right. There`s no surplus of either volts or amps when source
and load are connected. Its a match. Only a matched source and load
deliver all the power available in a source.

If we have too much resistance in our load, it doesn`t take as much
power as it could.

If we have too little resistance in our load, too much power is lost in
our source.

The perfect match of equal source and load resistances, with the
reactance neutralized, is the only condition permitting maximum power
transfer.

Somme amateurs want all the power they can get from their transmitters.

Best regards, Richard Harrison, KB5WZI

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Old February 26th 05, 10:21 PM
Cecil Moore
 
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Allan Herriman wrote:
S22 is fairly well defined.


What's the S22 of an IC-756PRO?
--
73, Cecil http://www.qsl.net/w5dxp

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Old February 26th 05, 10:27 PM
Cecil Moore
 
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Allan Herriman wrote:
S22 is fairly well defined.


What's the S22 of an IC-756PRO? With that figure,
S22^2 is defined as:

Power reflected from the network output divided by
Power incident on the network output.

Better yet, we can then calculate the reflected power
dissipated by the IC-756PRO.
--
73, Cecil http://www.qsl.net/w5dxp

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Old February 26th 05, 10:35 PM
Cecil Moore
 
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Rich Grise wrote:
And another thing - in a transmitter, the impedance matching only happens
at the one frequency, which is a lot different scenario from, say, a
stereo. This could be a confusion factor here.


Therefore, the key to converting the non-linear source to
an equivalent linear source lies in a Fourier analysis?
Do the other-than-fundamental terms in the Fourier analysis
encounter a low impedance or a high impedance?
--
73, Cecil http://www.qsl.net/w5dxp

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