On Sun, 05 Sep 2004 16:21:27 GMT, Richard Clark
wrote:

On Sun, 5 Sep 2004 11:05:24 -0500, "Richard Fry"
wrote:

I trust my contention is now clear to you.

Hi OM,

Actually no. Your reference, Mendenhall, specifically writes about
his design:

Hi All,

I would add further, Mendenhall's notes of his design, as the model of
clarity, include references, one of which is particularly notable and
estimable within this group:
"Treman [sic], F.E.; "Electronic and Radio Engineering";
Mc Graw - Hill Book Co.; 1955"
the same publication I've had since the same date that Geoff built his
transmitter. Geoff's attachments also include the data sheets from
Eimac which show quite plainly that ALL of his formulas and
computations are congruent with ALL sources of information in his
references.

Another reference:
"Goodman, Byron (Ed.); 'The Radio Amateur's Handbook';
American Radio Relay League; Newton, Conn.;
1966"
(I used to have that publication, back then, too)

I also vaguely note some inference of peculiar intermodulation
products that would be produced by a transmitter with 50 Ohm output
characteristic - in that I may be mistaken because when the verbiage
gets particularly dense to explain simple matters, I must admit my own
filters kick in. However, Mendenhall's work was not simply that of an
amateur's project, nor was it a school term paper, nor was it the
speculation of an engineering sales pitch.

The report I am drawing upon was Geoff's own Type Acceptance
application to the FCC which included all the technical specifications
of spurs, intermodulation products, stability, efficiency (80%), class
of operation, modulation, out-of-band responses.... I don't think I
need go much further. :-)

For those who wish to read the COMPLETE story of how to build a rig,
how to specify it, how to measure it, and to note how it exactly
conforms to conventional wisdom; then visit:
http://www.techatl.com/wrek/docs/gnm_0011.htm
where you will find all of one page of theory, and 40 odd pages of
reality:
The WREK 425 Watt RF power amplifier, also known as the
"Goat-Mitter" was designed by Geoffrey N. Mendenhall (dubbed the
Goatman by WREK announcer, Ed Esserman) and constructed entirely
with hand tools by Geoff and the WREK staff in August of 1968.

73's
Richard Clark, KB7QHC

Richard Fry wrote:
"I also vaguely note some inference of peduliar intermodulation products
that would be produced by a transmitter with 50 Ohm output
characteristics---"

First transmitting plant I worked in back in 1949 was that of KPRC /
KXYZ. These each used an RCA 5-C. Transmitters were 250-watt exciters
driving 5 KW water cooled linear final amplifiers. The interesting thing
about this plant was that the 950 KHz and 1320 KHz transmitters both fed
a common main antenna. Each station had its own directional tower on the
side.

The way to avoid intermodulation is to keep the foreign signals out of
the electronics so they don`t mix. Well designed and adjusted
pass/reject fikters in the transmission circuits of KPRC and KXYZ saw to
that.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote
Richard Fry wrote:
"I also vaguely note some inference of peduliar intermodulation products
that would be produced by a transmitter with 50 Ohm output
characteristics---"
_________

How do find it justified to assign a literal quote to me that I did not
write in the first place?

RF

Richard Fry wrote:
"How do (you) find it justified to assign a literal quote to me that I
did not write in the first place?"

A mistake?

Sorry if I misquoted Richard Fry on peculair intermodulation products.

The power hungry RCA 5 C`s with their linear amplifiers were later
replaced with RCA BTA5F`s which had Class C final amplifiers. Despite a
phony ceremonial switchover to the new equipment in which pads were
pulled from the audio lines to the new transmitters, the stations really
sounded the same before and after the equipment change.

Best regards, Richard Harrison, KB5WZI

"Richard Harrison" wrote
The way to avoid intermodulation is to keep the foreign signals
out of the electronics so they don`t mix. Well designed and
adjusted pass/reject fikters in the transmission circuits of
KPRC and KXYZ saw to that.
_____________

Thanks. You report more evidence that the source impedance did not match the
load impedance of these txs. If they did, each of these txs would absorb
the coupled signal of the other -- and neither of them would generate mixing
products.

RF

On Sun, 5 Sep 2004 14:53:47 -0500, "Richard Fry"
wrote:

|"Richard Harrison" wrote
| The way to avoid intermodulation is to keep the foreign signals
| out of the electronics so they don`t mix. Well designed and
| adjusted pass/reject fikters in the transmission circuits of
| KPRC and KXYZ saw to that.
|_____________
|
|Thanks. You report more evidence that the source impedance did not match the
|load impedance of these txs.

|If they did, each of these txs would absorb
|the coupled signal of the other -- and neither of them would generate mixing
|products.

Why would they? One is tuned to 950 KHz, the other to 1320 KHz, a
good part of an octave difference.

This is the same fuzzy logic that says that you can measure the output
Z of an amplifier at one frequency by injecting another signal at a
different frequency.

If it was this easy, the bother of load pull techniques wouldn't have
become popular and the norm.