Mike Coslo wrote:
Richard is right, There is the first ream!
Sorry, I'm a bit pippish today..........

Ignorance of s-parameter analysis, like ignorance of the
Smith Chart, is not a mortal sin.
--
73, Cecil http://www.qsl.net/w5dxp



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"Cecil Moore" wrote in message
...
Tam/WB2TT wrote:
I am not quite sure what you are saying. But, I ran a SPICE simulation
of
the following:
1V 1MHz source with resistor R0 feeding a 50 Ohm 250 ns transmission
line
shorted at the far end. Independent of R0, in steady state the voltage
at
the input end of the transmission line will be 1V. The effect of R0 is
to
limit how long it takes to reach steady state. For R0 = 50 Ohms, it is
one
cycle; for R0 = 500 Ohms, it is about 8 cycles, as eyeballed off the
waveform display.

Does SPICE report the steady-state forward and reflected waves
or just the superposition of those two waves? We all know what
they look like when superposed. The question is whether the
identity of the forward and reflected waves disappear after
they are superposed. To the best of my knowledge, the very
existence of standing waves requires the existence of a forward-
traveling wave and a rearward-traveling wave.

I have asked for examples of standing waves void of rearward-
traveling waves and none has been forthcoming.
--
73, Cecil http://www.qsl.net/w5dxp
It shows the composite voltage waveform, and the net current. Exactly what a
Bird wattmeter would do. Of course the Bird only shows you steady state,
Spice (SWCAD) swhows how you got there.

Tam/WB2TT

Cec et al, what have circulators, S-parameters, etc. to do with HF ?

Tam/WB2TT wrote:
It shows the composite voltage waveform, and the net current. Exactly what a
Bird wattmeter would do.

That's not what a Bird wattmeter does. A Bird wattmeter possesses
a directional coupler. SPICE apparently does not. Is it possible
to add a directional coupler to SPICE? If you know the Z0, the net
voltage/current magnitudes/phases, it should be possible to use
phasor addition/subtraction to obtain the forward and reflected
components, just like the Bird wattmeter does.
--
73, Cecil http://www.qsl.net/w5dxp



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Not much but neither does much of this thread regarding my original query.
I hope someone that understands the question can answer in a way that my
feeble brain can comprehend. At least we're eliminating what's not the
answer.
73
Hank WD5JFR

"Reg Edwards" wrote in message
...
Cec et al, what have circulators, S-parameters, etc. to do with HF ?

Concept below

However this is not an accurate model of a transmitter.

For an example, take an old Heathkit DX-100 generating a measured 180 watts
of CW RF into a matched 50 ohm load. To do this, it does NOT also dissipate
180 watts of RF into some "virtual" internal RF load in the DX-100. In
fact, the PAs and power supply in the DX-100 could not produce a total RF
output power of 360 watts without exceeding their ratings.

The dissipation in the PA is essentially related only the DC to RF
conversion efficiency of the PA, which in this case probably is about 75%,
max (Class C). So a PA input power of about 240 watts DC is required to
produce 180 watts of RF output power. The other 60 watts of plate input
power is converted to heat by the PA tube anodes.

The entire RF output generated by the PA stage is applied virtually 100% to
the output connector. How much of that is absorbed by the load connected
there is a function of load SWR and system losses.

- RF
________________

"alhearn" wrote
If you leave out the complex part of impedences for the moment and
think of 100 volt generator that has a 50 ohm internal impedance
driving a 50 ohm load, current is 1 amp and the power dissipated by
the load is 50 watts. There is also 50 watts dissipated by the
generator's internal impedance, for a total of 100 watts dissipated by
the entire system. Therefore, the "available" power for this generator
is 50 watts.

Reg Edwards wrote:
Cec et al, what have circulators, S-parameters, etc. to do with HF ?

What does scattering have to do with antenna systems with
reflections???? Maybe you should download the HP AN 95-1?
It's available at:

http://www.sss-mag.com/pdf/hpan95-1.pdf

From _Fields_and_Waves_in_Communication_Electronics_ by
Ramo, Whinnery, and Van Duzer. "11.09 Scattering and
Transmission Coefficients ... This article introduces two
of the *most* useful (two-port analysis) forms based
on wave quantities." This is a (c)1965 book, a later version
of a classic fields and waves (c)1944 book by Ramo & Whinnery.
--
73, Cecil http://www.qsl.net/w5dxp



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Henry Kolesnik wrote:
Not much but neither does much of this thread regarding my original query.

They have a lot to do with the subject of the thread. :-)

I hope someone that understands the question can answer in a way that my
feeble brain can comprehend. At least we're eliminating what's not the
answer.

Back a dozen years ago, or so, Mr. Bruene tried to 'ping' a final
amp with a slightly off-frequency signal to ascertain the output
impedance of the amp and he published his results in QST. His apparent
error was that he didn't do it at the frequency of operation of the
amp and he didn't know what the 'Q' of a final amp really is. There
has been a running argument ever since, probably best documented in
QEX magazine. There are basically two sides to the argument.

1. If load-pulling causes a falloff of power on each side of the
operating point, then the system is conjugately matched. That
conjugate match includes such things as non-dissipative resistances.

2. Conjugate matches do not exist in a typical amateur system.

Brilliant minds have been trying to prove one or the other and
both sides (IMO) have failed in that proof. There is no final,
definitive proof of either position. If there was such, there
would be no argument. That's why we cannot answer
your question. The picture is further clouded by a definition.
If reflected energy makes its way back into the final amp, it
was never generated in the first place, by definition.
--
73, Cecil http://www.qsl.net/w5dxp


"Reg Edwards" wrote:
Cec et al, what have circulators, S-parameters, etc. to do with HF ?



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Then why can high SWR on a TV Tx cauuse ghosts or smearing on the TV Rx?
Hank WD5JFR
"Cecil Moore" wrote in message
...
Henry Kolesnik wrote:
Not much but neither does much of this thread regarding my original
query.

They have a lot to do with the subject of the thread. :-)

I hope someone that understands the question can answer in a way that my
feeble brain can comprehend. At least we're eliminating what's not the
answer.

Back a dozen years ago, or so, Mr. Bruene tried to 'ping' a final
amp with a slightly off-frequency signal to ascertain the output
impedance of the amp and he published his results in QST. His apparent
error was that he didn't do it at the frequency of operation of the
amp and he didn't know what the 'Q' of a final amp really is. There
has been a running argument ever since, probably best documented in
QEX magazine. There are basically two sides to the argument.

1. If load-pulling causes a falloff of power on each side of the
operating point, then the system is conjugately matched. That
conjugate match includes such things as non-dissipative resistances.

2. Conjugate matches do not exist in a typical amateur system.

Brilliant minds have been trying to prove one or the other and
both sides (IMO) have failed in that proof. There is no final,
definitive proof of either position. If there was such, there
would be no argument. That's why we cannot answer
your question. The picture is further clouded by a definition.
If reflected energy makes its way back into the final amp, it
was never generated in the first place, by definition.
--
73, Cecil http://www.qsl.net/w5dxp


"Reg Edwards" wrote:
Cec et al, what have circulators, S-parameters, etc. to do with HF ?



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"Cecil Moore" wrote in message
...
Dave wrote:

"Cecil Moore" wrote:
What I am willing to discuss in detail is what happens at a Z0-match
point (x) in an antenna system with reflections - something like the
following:

what you are willing to discuss is irrelevent as it has nothing to do
with
the original topic which was about what happens in the transmitter.

Uhhhh Dave, the original topic is the Subject: line. If anything,
what happens inside a transmitter is the irrelevant subject since
appreciable reflections hardly ever reach the typical ham transmitter.


here is the original:

I know that any power not dissipated by an antenna is reflected back to the
transmitter. Then the transmitter "reflects" this reflection back to
antenna, ad nauseum until its all gone. I also know that a short or an open
is required to reflect power and I'm searching for which it is, an open or a
short. I'm inclined to think it's a virtual open but I'm at a loss to
understand that and I wonder if someone has a good explanation or analogy
and some math wouldn't hurt.
tnx
Hank WD5JFR

obviously not about what is going on at some contrived transmission line
joint.


For these typical conditions, all voltages and currents are either
in-phase or 180 degrees out of phase at the match point (x), which
makes a power analysis the most simple analysis of all.

that should read "For these specific conditions", those conditions are
hardly 'typical', they are a very exactly contrived example which makes
it
easy to compare powers.

No, those are typical conditions, where the ham radio antenna system
is tuned to a Z0-match by a tuner, either external or internal. It is
not a "very exactly contrived example" at all. It is absolutely typical
of any ham radio installation where the final amp sees close to a 1:1 SWR
and that is the great majority. At the Z0-match point at the input of
every properly tuned transmatch, the voltages and currents are either in
phase or 180 degrees out of phase. If you don't know that, it is no
wonder that you label my power analysis stuff as "contrived".

of course it is contrived. no one uses loads of those exact impedances, or
lengths of coax like you do.