On May 20, 1:08*pm, K7ITM wrote:
On May 20, 6:25*am, Wimpie wrote:









On 20 mayo, 14:42, Cecil Moore wrote:

On May 19, 5:22*pm, Wimpie wrote:

Many amateurs built and / or designed their own HF PA (and
other circuitry relevant to the hobby). Do you really think that they
all considered every component to be a transmission line?

You apparently have not comprehended what I am trying to say. When one
is designing a piece of equipment, whatever works, works. Please don't
confuse design/analysis techniques and rule-of-thumb shortcuts with
the underlying principles supporting the laws of physics. Enumerating
all the design techniques in the world does not tell us anything about
what is happening in reality to those photonic fields and waves that
necessarily must obey the laws of physics.

Even DC impulses travel at the speed of light. Electron drift velocity
is much, much slower than the speed of light. Everything EM is
photonic in nature. Photons must obey the laws of physics known to
exist for photons. There is simply no getting around that fact. All of
the magical thinking, hand-waving, design/analysis shortcuts, and
rules-of-thumb in the world are not going to change those facts of
physics.

Hello Cecil,

When one knows the physics well, one knows what to take into account
and what to left out, just to finish the job efficiently. It seems you
don't understand that principle. Is this some lack of understanding
physics?

Do you really believe that when designing an optical detector
(completely off-topic) I don't bother about noise due to quantisation?

If you do not understand those physical limitations (including. the
difference between the two IEEE definitions of impedance) you will
never understand what is actually happening in reality inside (or
outside of) an RF source. I don't know what else to say.
--
73, Cecil, w5dxp.com

Regarding PA's and IEEE definitions, *I don't get paid for my
knowledge (if present?), but just for delivering what has been
agreed.

You introduced photons here; I think you may also introduce
thermodynamics of electrons as that may be of more importance at our
frequencies. *I do not violate agreed laws of physics, but only leave
out higher order effects that are insignificant in my opinion.

Wim
PA3DJSwww.tetech.nl

Beyond just understanding what parts of the physics theory are
important in a particular situation, there's the more general concept
of compartmentalizing things. *The original question was about
transmitter output impedance, and to answer that question, you really
don't have to get into interminable discussions about what goes on in
some arbitrary load. *The only things that matter with respect to the
load are the voltage, current and phase between them at the output
port of the source.

A perfectly valid reason to talk about the load -- what you connect to
the source output port -- is how you can configure that load to
establish a variety of load conditions so that you can see how the
source behaves, and from that, derive the source impedance. *In fact,
some months past now, Wim and I had some email exchanges about that.
The emails were very valuable to me, because they got me thinking
about various arrangements of the equipment I have to enable accurate
measurements, and brought up points about things that go on _inside_ a
typical RF power amplifier that can cause you to measure things
inaccurately. *For example, an ALC loop with a relatively slow
response time could make you think that the amplifier output impedance
is quite low if you take measurements more slowly than the response
time of the ALC loop. *You might even decide that it makes sense to
talk about amplifier output impedance as a function of frequency
offset relative to the output frequency (or some similar way to talk
about the "time response" of the output impedance). *It all depends on
what you want to _do_ with your output impedance number once you have
it, and that's something I don't recall seeing much of in this thread,
nor in any of the many previous threads covering the same old ground.

Cheers,
Tom


I'm trying to locate the John Smith who signs his posts with 'js'.
Does any one know his call sign? Or perhaps his email address?

Thanks, Walt, W2DU