See minor point at end....

On Tue, 16 Dec 2008, NoSPAM wrote:

Date: Tue, 16 Dec 2008 19:33:53 -0500
From: NoSPAM
Newsgroups: rec.radio.amateur.homebrew
Followup-To: rec.radio.amateur.homebrew
Subject: Doubling

"Telstar Electronics" wrote in message
...
Nonsense... please read the definition section at
http://minicircuits.com/pages/pdfs/doub9-2.pdf

You are grasping at straws trying to defend your beliefs. Their definition
only applies to their products. You should have read the entire article. If
you consider the single discontinuity of an ideal diode at the origin as
nonlinear, then you are correct. In practice, two Class AB or B amplifiers,
operated over their most linear region (each individually producing harmonics
and intermodulation over 40 dB down from the fundamental), can be used in a
push-push configuration to produce even order harmonics. I believe "Stray
Dog" and I both have shown that single ended Class A amplifiers DO produce
harmonics.

The Mini Circuits "doubler" is, I believe, essentially a full wave rectifier
using Schottky diodes. If the diodes were ideal, i.e. had no highly
non-linear region at low voltages, there would be no fundamental output or
odd order harmonics. From my earlier discussion of full wave rectification,
perfect diodes would produce the fourth harmonic 14 dB lower than the second
harmonic, and the sixth harmonic slightly over 7 dB down from the fourth.
The Minicircuits device produces at its output the fundamental and odd order
harmonics in addition to the desired even order harmonics. It also requires
a drive level of between 0 and 20 dBm. Too low a drive and the doubling
action disappears; too high a drive and the amplitude of the higher harmonics
increases (until the device burns out).

Some further research into the push-push doubler reveals that two sharp
cutoff pentodes would do a better job than triodes for this application. Also
junction field effect transistors follow square law characteristics over a
fairly wide range making them ideal in frequency doubler operation too. It
is also possible to nearly achieve ideal diode behavior with the use of very
high gain amplifiers with feedback through the diode. See the following
Intersil ap-note for details: http://www.intersil.com/data/an/an1114.pdf.

My post of the graphs has not appeared on the "alt.binaries.ham-radio" Usenet
newsgroup, even on my nntp server which still insists that the newsgroup
exists. I'll try again using "alt.binaries.radio.misc" this time.

I learned many years ago that even non-binary newsgroups _can_ carry
attached files (in any format), but then later learned that ISPs can
configure their newsservers in ways that can prevent you from making a
post with an attached file. I discovered that when a post I tried to make
with a new ISP gave me an error message. It is possible that you have an
ISP that somehow prevents either/or the body and/or the attached file from
being posted either dependently or independently from each other. And,
tech support people don't understand this, and sometimes even the geeky
whips who are sysops don't understand it, either.

You might actually do better if you can set up a "personal" web page and
just load the jpeg or gif files with associated URLs.

My thanks
go to "Stray Dog" for his efforts in also experimenting with a single ended
6C4 triode.

Thank you for taking the time to read about my "discovery" and making an
acknowledgement. But, most of the tube transmitter schematics I ever
looked at for driver/buffer/multiplier stages sure looked like they
were running linear bias voltages on the control grids instead of
class C biases. And, it was quite an experience to see, on a quality
oscilloscope, that second harmonic come out of nothing as the air variable
capacitor was adjusted for the second harmonic frequency. And, the S-meter
on the receiver, tuned to the second harmonic frequency, also bumped up a
few S units, too, at the same time.


73, Dr. Barry L. Ornitz WA4VZQ