"Non-dissipative Source Resistance"
 

On Sun, 13 Jun 2010 13:36:53 -0700 (PDT), Richard Fry
wrote:


Mendenhall's paper shows "RF spectrum showing distortion products"
that are 30dB down.

Not near the resonant frequency of the output tuning/matching network.

Another subjective term. How near is near? All products that
Mendenhall shows in the illustration titled "RF spectrum showing
distortion products" are 30dB down and those distortion products fall
between modulation sidebands (unless you are speaking of doubling and
trippling of the carrier frequency).

Returning to the amplifier of his own design, in his classic WREK
engineering report [you seem shy of acknowledging your authority's
work here] submitted to the FCC. Now, when I say "of his own design,"
I mean by him personally, at the bench, using tools, assembling
components against his own schematic. He explicitly states:
"Distortion at 100% = 1%." At "frequency removed from carrier" from
-35dB to -73dB out to "600 Khz and beyond."
"Harmonic and spurious radiation" at least -70dB.
"Harmonic distortion" at 100% worst case 2.3%
"Plate efficiency of 70% to 80%"
"Total efficiency of 68%" [plate power in / RF power out]
operating Class C.

And of course his statement that sends minds reeling:

"It was thus necessary to determine the plate load impedance
= (Eb - Emin) / I1
~= Eb/ Idc
~= 1000 Ohms
[Not very far from Walt's determination of 1400 Ohms from his own
bench.]
"Since this was to be coupled into a Z output of 50 Ohms, a impedance
transformation of 20:1 was needed. This was accomplished by using a
voltage divider of two series capacitors to series tune the plate
circuit."

His EIMAC reference found in other, later published papers conform to
every detail in his engineering report to the FCC and in those same
later papers. In fact, they offer a multitude of operational
parameters for a variety of tubes at many power levels, across many
bands and classes of operation.

73's
Richard Clark, KB7QHC

"Non-dissipative Source Resistance"
 

On Jun 13, 5:44*pm, Richard Clark wrote:
*All products that
Mendenhall shows in the illustration titled "RF spectrum showing
distortion products" are 30dB down...

The relevant illustration applying to the generation of r-f
intermodulation from external signals was linked in my original quote
from Mendenhall's paper on this subject in this thread, which link I
repeat below.

It shows that the "tunrnaround loss" for external signals 0.8 MHz
offset from the carrier is as little as 5 dB, just as I posted.

By limiting limiting your understanding to the performance of an r-f
amplifier having no external influences you are missing the point of
the Mendenhall paper I referred to.

http://i62.photobucket.com/albums/h8.../TAL_Chart.gif

RF

"Non-dissipative Source Resistance"
 

On Mon, 14 Jun 2010 01:56:22 -0700 (PDT), Richard Fry
wrote:

By limiting limiting your understanding to the performance of an r-f
amplifier having no external influences you are missing the point of
the Mendenhall paper I referred to.

This is repetitive without being informative. I am satisfied with
Mendenhall's clear statements about plate resistance in how to fine
tune finals - a paper that is obviously on-topic. I am satisfied with
his WREK design (as was the FCC). I see he observed standard methods
of design and cites accessible authorities that guide industry. I
don't need to elaborate what he offers by mincing around the issue
with interpretation, inference, and suggestion.

To offer what you think is contrary evidence goes well toward
impeaching your own authority. There is no amount of discussion or
even agreement that can balance that contradiction. From the content
of your other discussion, you are arguing both sides, or you are
turning this on the pivot of an opaque detail known only to you.

I am satisfied that the general readership has all the details. Or
could ask for them if this was interesting.

73's
Richard Clark, KB7QHC

"Non-dissipative Source Resistance"
 

On Jun 14, 2:01*pm, Richard Clark wrote:

I am satisfied that the general readership has all the details.

So am I.

What they mean to each reader depends on his/her ability and
willingness to comprehend what was given in the Mendenhall paper I
quoted, and not to refer to data taken on an r-f amplifier operating
under conditions having no specific relevance to the Mendenhall paper
about turnaround loss.

RF