"Telstar Electronics" wrote in message
...

You mean to tell me that you take a clean sine wave... pass it
through... say a single-ended class A amp... and you can put a tank on
the output of that amplifier... and tune for a harmonic? You will get
nothing.

Of course you will. No active device is perfect.

I decided to illustrate the fact that a single ended triode operated in
Class A can produce harmonics. For a tube, I used a 6C4 (1/2 of a 12AU7)
operated with 300 volts on the plate, a grid bias voltage of -7 volts,
driven with a pure sine wave of 14 volts peak-to-peak. The high driving
voltage was chosen to illustrate my earlier points, but the stage _IS_
operated Class A with the plate current between cutoff and saturation.

Since the "rec"groups are not supposed to have binaries in them, I placed
the graphics as PDF attachments to a post entitled "Harmonics generated by
a Class A stage" in the "alt.binaries.ham-radio" newsgroup. If anyone
wishes to see these curves and their newsgroup provider does not provide
this group, I apologize. I believe Google Groups may not provide binaries,
so I suggest getting a real newsreader and a good newsfeed.

The first graph is entitled "Transconductance.pdf" and it shows the plate
current as a function of the grid voltage. This data was obtained directly
from the General Electric datasheet, ET-T1604 dated March, 1960. Since
Excel stinks when plotting and doing calculations with data that is not
best expressed in a bar chart, I used an evaluation copy of PSIPlot from
Poly Software International (http://www.polysoftware,com) to generate the
plots. {Real scientists and engineers never use a bar chart except when
making presentations to brain challenged management!} :-)

The driving waveform and the resultant plate current waveform are shown in
the graph entitled "Waveforms.pdf". The obvious flattening is due to
cutoff being approached at the crest of the driving waveform. After all,
the transconductance curve is not perfectly a straight line.

Finally, the spectrum of current waveform is plotted in the graph called
"Spectrum.pdf". The spectrum has been normalized with respect to the DC
output. The scale of the X-axis is slightly off but it was not worth my
time correcting it. The fundamental is about 60 to 70 percent of the DC
output, and the second harmonic is about 40 percent of the DC output. All
higher harmonic are less than one percent of the DC output except the
fifth. Higher harmonics are still greater than one tenth of a percent of
the DC up to the _13th_ harmonic. Harmonics beyond the 14th are still
readily measured.

In conclusion, even single ended Class A amplifiers generate harmonics.
If a lower driving voltage were used, the amplitudes of the harmonics would
be reduced, but the fundamental would also be reduced. Please follow-up to
the "rec.radio.amateur.homebrew" newsgroup. Golden-eared audiophools will
be ignored.

73, Dr. Barry L. Ornitz WA4VZQ

On Mon, 15 Dec 2008 23:29:35 -0500, "NoSPAM"
wrote:

"Telstar Electronics" wrote in message
...

You mean to tell me that you take a clean sine wave... pass it
through... say a single-ended class A amp... and you can put a tank on
the output of that amplifier... and tune for a harmonic? You will get
nothing.

Of course you will. No active device is perfect.

I decided to illustrate the fact that a single ended triode operated in
Class A can produce harmonics. For a tube, I used a 6C4 (1/2 of a 12AU7)
operated with 300 volts on the plate, a grid bias voltage of -7 volts,
driven with a pure sine wave of 14 volts peak-to-peak. The high driving
voltage was chosen to illustrate my earlier points, but the stage _IS_
operated Class A with the plate current between cutoff and saturation.

Did you bypass the cathode resistor or not ?

All active elements are more or less nonlinear, so if you need more or
less linear amplification, you need to use feedback/feedforward.

A non-bypassed cathode/emitter resistor will greatly improve the
linearity of a single stage.

Paul OH3LWR

On Dec 14, 8:22*pm, "NoSPAM" wrote:
Actually you do not need any nonlinearity to make a doubler (quadrupler, etc.).

Nonsense... please read the definition section at
http://minicircuits.com/pages/pdfs/doub9-2.pdf

On Tue, 16 Dec 2008, Paul Keinanen wrote:

Date: Tue, 16 Dec 2008 09:47:22 +0200
From: Paul Keinanen
Newsgroups: rec.radio.amateur.homebrew
Subject: Doubling

On Mon, 15 Dec 2008 23:29:35 -0500, "NoSPAM"
wrote:

"Telstar Electronics" wrote in message
...

You mean to tell me that you take a clean sine wave... pass it
through... say a single-ended class A amp... and you can put a tank on
the output of that amplifier... and tune for a harmonic? You will get
nothing.

Of course you will. No active device is perfect.

I decided to illustrate the fact that a single ended triode operated in
Class A can produce harmonics. For a tube, I used a 6C4 (1/2 of a 12AU7)
operated with 300 volts on the plate, a grid bias voltage of -7 volts,
driven with a pure sine wave of 14 volts peak-to-peak. The high driving
voltage was chosen to illustrate my earlier points, but the stage _IS_
operated Class A with the plate current between cutoff and saturation.

Did you bypass the cathode resistor or not ?

I did the same experiment that he did (6C4) only ran the cathod at
chassis, and grid through an RF choke, and 100 vDC on plate, and drove at
about 1/2-1 volt and that is zero bias, no need for cathode cap bypass, and
I got gain and second harmonic.

All active elements are more or less nonlinear, so if you need more or
less linear amplification, you need to use feedback/feedforward.

A non-bypassed cathode/emitter resistor will greatly improve the
linearity of a single stage.

I'm still waiting for any "expert" comments from anyone who would care to
speculate on the contributions, from oscillator harmonic content vs
contribution from harmonic distortion in the amplifier.

Paul OH3LWR

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

73, Dr. Barry L. Ornitz WA4VZQ

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

On Dec 15, 11:29*pm, "NoSPAM" wrote:
"Telstar Electronics" wrote in message

...

You mean to tell me that you take a clean sine wave... pass it
through... say a single-ended class A amp... and you can put a tank on
the output of that amplifier... and tune for a harmonic? You will get
nothing.

Of course you will. *No active device is perfect.

Hey OM
The nature of the beast is:
single ended amps produce rich even harmonics
Push Pull amps produce rich odd harmonics

so you can gits odd harmonics from single ended but they are poor like
me.

73 OM
n8zu