On 14 jun, 20:00, Richard Clark wrote:
On Mon, 14 Jun 2010 06:06:06 -0700 (PDT), Wimpie
wrote:

23 pages is not that much as graphs and circuit diagrams dominate. *If
you can provide me a circuit diagram I will figure out whether I can
simulate it or not.

Hi Wim,

I'm glad you wish to examine this more. * I will send you Mendenhall's
400W FM design done 42 years ago to this month and nearly day. *I will
also send a partial schematic for Walt's TS-830s.

Mendenhall's is not very different from your own model except with a
far more powerful VHF Tube, however, it is a tetrode design too.
Walt's is a pair of pentodes. *See what you can do.

Fully agree with the low cathode Q, therefore it doesn't affect the
simulations results significantly.

Why a Common Grid design for a tetrode tube?

Because I built such circuit myself based on two PL519 television
tubes and to reduce the number of runs to tune the amplifier in
simulation (I still need some time to work also).
*

Tell me what Q I should use (evt, give me component values) in the
simulation, and I will change it for you.

15 is one that Terman cites, and Mendenhall cites Terman, and Walt's
(if I recall correctly) also find a similar value. *Given your
especially low frequency simulation, component values are way out from
those commonly encountered in HF/VHF work.

Over here 3.6 MHz is an amateur band, we may even go lower than that.
I will change the real class C ciruit to Q = 15. Q = Rload/XL?


No, your paper lacks focus by trying to be all things (tubes, mosfets,
Class AB, Class C).

This is to support my statement that under real world amateur
conditions many PAs do not obey ZL = Zout*. If I have some time I will
add a push-pull transfomer coupled amplifier also.

Then you should do the finals deck for a transistor rig for that
topology. *It would bring you into the 21st century (even if the
details still date from the 1970s). *You will also find more
simulation options.

simulation is general practice in the design flow, I know it has
limitations. Of course I could use ADS, but most people don't have
that at home, so I decided to use spice as this is used by many.

One of the titans of linear design, Bob Pease of National
Semiconductor had little sympathy for those who discovered the
problems of simulation. *However, those who read his work were sure to
avoid pain and trauma. *Consult:http://www.national.com/rap/

Having said that, it is somewhat ironic that we all use simulation for
antennas - so we are all aware of limitation and possibility. *I have
used many simulators from a spectrum of disciplines.

If you believe I am so wrong, why don't you present some simulations
to show that my original statement is completely wrong?

You have more time and passion for it. *

I have very limited time for this, so we have to keep it very
efficient.

I have already had a career in
testing these issues specifically and proof is at the bench. * I was
trained to demanding methods for this and I worked with the most
accurate instruments in the world. *However, I don't expect equal
results. *If you wish to work further with the two schematics I send
you, then that would interest me far more than the banalities of
photonic explanations and spreadsheet solutions.

I am not saying anything you have done is wrong, I am saying that your
style is getting in the way of communication. *It reads like a
detective novel, not a like presentation. *You discover conclusions,
you don't seem to test for expectations. *Surprise and mystery arrive
haphazardly through the narrative. *Inconsequential details are mulled
over like Holmes describing the characteristics of cigar ash to
Watson. *

Except the high Z value for the Common Cathode amplifier, all results
are as expected. Otherwise I did not make my statement on the output
impedance of PAs.


You are trying to do too many things in one place and the topic begins
to blurs and the goal is distracted. *For instance, this thread's
subject line of "what happens to reflected energy?" is never
summarized in your final conclusion - that is not good reportage. *I
went to that last section and saw that discussion missing. *Closer
examination revealed it by parts as seemingly trivial observations.

You disputed my statement on Zout and came up with the "what IS it"
attitude, I only provided information so that other people can get
their own opinion. I prefer to keep the focus on that.


For style, start with a good grounding. *Establish a base line. *Do a
Monte Carlo analysis of a known design with known characteristics.
Then introduce a hypothesis tied to one variable. *Push the variable
and note how it either conforms or strays from your hypothesis.
Present your work. *Have a discussion to shake out problems of
understanding (from anyone). *Then move on to either shift the
topology, or further stress the existing design. *Build on a solid
foundation.

This is not a thesis, I just did some simulation to show that things
can be different.

Schematics will follow as soon as I can make their file sizes suitable
for email servers (about 1-2 MB).

73's
Richard Clark, KB7QHC

Before I am going to spend lots into time this, some points:

1. Do you accept the "measuring" method with injecting a signal with
slight frequency difference as mentioned in the document?

2. Do you accept the way of presentation (envelope change versus time
and converted to output VSWR as used in the document)?

3. Do you accept B^2 spice A/D professional, version for as suitable
platform?

If we cannot agree on this, it is of no use to continue.

I limit the simulation to low HF frequencies as based on a circuit
diagram alone we cannot guess the parasitics for high HF/VHF use and
this may be food for more discussion. Please also mention what
components you want into the simulation as simulating a full TS830
will take to long.

All relevant info will be made available to the group, inclusive
original circuit diagrams and the diagrams I used for simulation. I
hope that I can get a suitable simulation model for the tubes.

Regarding circuit diagrams, can you reduce the color depth (gray scale
or B/W) and convert them to PNG as this is non-lossy coding.

I am looking forward to the results.

Best regards,


Wim
PA3DJS
www.tetech.nl