In article , Roy Lewallen
writes:

Avery Fineman wrote:
. . .
Making practical, reproducible active multipliers in the home shop
is, practically, a trial-and-error process involving playing with cut-
off bias of the active device input, energy and harmonic content of
the source, and Q of the multiplier's output stage. In the past I've
made tripling-in-the-plate pentode crystal oscillators using
fundamental frequency quartz but those were highly dependent on
getting the highest impedance tuned plate circuit and needed
scope viewing to check output waveforms. Not very reproducible.
There's no "easy" way to do it that will "work every time" despite
the claims of many. :-)
. . .

While that's certainly true of multipliers in general, I've certainly
found it very easy to make repeatable doublers with a two transistor
push-push stage. Driving it with about zero bias and a large enough
signal to get it to conduct on at least a good fraction of each cycle
gives plenty of harmonic energy. A collector circuit with decent Q will
take care of most higher harmonics, although a simple filter following
the stage is usually adequate for more demanding applications. The
fundamental can be nulled out reasonably well with a pot between
emitters with a grounded center tap. I'd think a push-pull tripler would
be nearly as easy, but I haven't had occasion to make one.

Okay. I can't agree that they are "easy" after having enough
occasions to make several. :-)

Your mileage, of course, varies.

Several simple diode and transistor multipliers are described in Chapter
5 of _Experimental Methods in RF Design_, which I heartily recommend for
the homebrewer and experimenter.

A diode doubler using a toroid transformer, pair of diodes and a tuned
circuit in the output works fine right off the paper pad and slide-rule (or
calculator) numbers. Typically the source is a distorted sinewave
from either another multiplier or an oscillator. Rocket science it ain't.

BREADBOARD. A most handy part of the bench tools. Recommended
first. Especially for those purist hobbyists who think that digital
circuits
aren't "real radio." :-)

Playing with bias on a transistor multiplier stage is fine for optimizing a
multiplication but all it is is play when there's nothing to compare one
bias setting with another as to power output at the desired multiple.
A spectrum analyzer isn't an absolute need, by the way, there's other
ways to measure the harmonic content. Is that in "Experimental
Methods..." published by the ARRL? [I'm pushing work-on-the-bench,
not books, pardon my attitude that has resulted from years of having
to produce hardware results, not paper reports]

Len Anderson
retired (from regular hours) electronic engineering person

In article , Roy Lewallen
writes:

Avery Fineman wrote:
. . .
Making practical, reproducible active multipliers in the home shop
is, practically, a trial-and-error process involving playing with cut-
off bias of the active device input, energy and harmonic content of
the source, and Q of the multiplier's output stage. In the past I've
made tripling-in-the-plate pentode crystal oscillators using
fundamental frequency quartz but those were highly dependent on
getting the highest impedance tuned plate circuit and needed
scope viewing to check output waveforms. Not very reproducible.
There's no "easy" way to do it that will "work every time" despite
the claims of many. :-)
. . .

While that's certainly true of multipliers in general, I've certainly
found it very easy to make repeatable doublers with a two transistor
push-push stage. Driving it with about zero bias and a large enough
signal to get it to conduct on at least a good fraction of each cycle
gives plenty of harmonic energy. A collector circuit with decent Q will
take care of most higher harmonics, although a simple filter following
the stage is usually adequate for more demanding applications. The
fundamental can be nulled out reasonably well with a pot between
emitters with a grounded center tap. I'd think a push-pull tripler would
be nearly as easy, but I haven't had occasion to make one.

Okay. I can't agree that they are "easy" after having enough
occasions to make several. :-)

Your mileage, of course, varies.

Several simple diode and transistor multipliers are described in Chapter
5 of _Experimental Methods in RF Design_, which I heartily recommend for
the homebrewer and experimenter.

A diode doubler using a toroid transformer, pair of diodes and a tuned
circuit in the output works fine right off the paper pad and slide-rule (or
calculator) numbers. Typically the source is a distorted sinewave
from either another multiplier or an oscillator. Rocket science it ain't.

BREADBOARD. A most handy part of the bench tools. Recommended
first. Especially for those purist hobbyists who think that digital
circuits
aren't "real radio." :-)

Playing with bias on a transistor multiplier stage is fine for optimizing a
multiplication but all it is is play when there's nothing to compare one
bias setting with another as to power output at the desired multiple.
A spectrum analyzer isn't an absolute need, by the way, there's other
ways to measure the harmonic content. Is that in "Experimental
Methods..." published by the ARRL? [I'm pushing work-on-the-bench,
not books, pardon my attitude that has resulted from years of having
to produce hardware results, not paper reports]

Len Anderson
retired (from regular hours) electronic engineering person

In article , Roy Lewallen
writes:

Avery Fineman wrote:
. . .
Making practical, reproducible active multipliers in the home shop
is, practically, a trial-and-error process involving playing with cut-
off bias of the active device input, energy and harmonic content of
the source, and Q of the multiplier's output stage. In the past I've
made tripling-in-the-plate pentode crystal oscillators using
fundamental frequency quartz but those were highly dependent on
getting the highest impedance tuned plate circuit and needed
scope viewing to check output waveforms. Not very reproducible.
There's no "easy" way to do it that will "work every time" despite
the claims of many. :-)
. . .

While that's certainly true of multipliers in general, I've certainly
found it very easy to make repeatable doublers with a two transistor
push-push stage. Driving it with about zero bias and a large enough
signal to get it to conduct on at least a good fraction of each cycle
gives plenty of harmonic energy. A collector circuit with decent Q will
take care of most higher harmonics, although a simple filter following
the stage is usually adequate for more demanding applications. The
fundamental can be nulled out reasonably well with a pot between
emitters with a grounded center tap. I'd think a push-pull tripler would
be nearly as easy, but I haven't had occasion to make one.

Okay. I can't agree that they are "easy" after having enough
occasions to make several. :-)

Your mileage, of course, varies.

Several simple diode and transistor multipliers are described in Chapter
5 of _Experimental Methods in RF Design_, which I heartily recommend for
the homebrewer and experimenter.

A diode doubler using a toroid transformer, pair of diodes and a tuned
circuit in the output works fine right off the paper pad and slide-rule (or
calculator) numbers. Typically the source is a distorted sinewave
from either another multiplier or an oscillator. Rocket science it ain't.

BREADBOARD. A most handy part of the bench tools. Recommended
first. Especially for those purist hobbyists who think that digital
circuits
aren't "real radio." :-)

Playing with bias on a transistor multiplier stage is fine for optimizing a
multiplication but all it is is play when there's nothing to compare one
bias setting with another as to power output at the desired multiple.
A spectrum analyzer isn't an absolute need, by the way, there's other
ways to measure the harmonic content. Is that in "Experimental
Methods..." published by the ARRL? [I'm pushing work-on-the-bench,
not books, pardon my attitude that has resulted from years of having
to produce hardware results, not paper reports]

Len Anderson
retired (from regular hours) electronic engineering person

Avery Fineman wrote:
. . .
Playing with bias on a transistor multiplier stage is fine for optimizing a
multiplication but all it is is play when there's nothing to compare one
bias setting with another as to power output at the desired multiple.
A spectrum analyzer isn't an absolute need, by the way, there's other
ways to measure the harmonic content. Is that in "Experimental
Methods..." published by the ARRL? [I'm pushing work-on-the-bench,
not books, pardon my attitude that has resulted from years of having
to produce hardware results, not paper reports]

Len Anderson
retired (from regular hours) electronic engineering person

Yes, that book is published by the ARRL. Its authors, Wes Hayward,
W7ZOI; Rick Campbell, KK7B; and Bob Larkin, W7PUA have, unlike so many
authors, spent careers doing just what you and I have had to do --
produce hardware results. Of them, I know Wes the best, having been
friends with him for about 30 years. After a stint at Boeing long ago,
Wes was a design engineer in the spectrum analyzer group at Tektronix
for a number of years, where his designs were incorporated in a number
of state-of-the-art spectrum analyzers. He went from there to TriQuint
semiconductor, where he designed many RF components which are in daily
use in probably millions of cell phones and other wireless products. He
recently retired and has been doing some consulting. His publications in
amateur journals, spanning decades, are legendary and many are seminal.
I don't know Rick quite as well, but he's also a very capable and
accomplished engineer (in spite, one might say, of his Ph.D. and period
in academia). For years now, he's also worked as a design engineer at
TriQuint. To get a feel for his approach to solving real problems, check
out the articles he's published over the years in QST on phasing type
direct conversion receivers. Bob I don't know at all, but Wes speaks
very highly of him, and I have absolute confidence in Wes' judgement of
skill.

There's nothing in that book that hasn't been built and tested, and
designed to be repeatable. And everything has been designed by people
who really know what they're doing. This isn't a book of
kluged-it-up-on-the-bench-and-made-one-work-once projects as so many
are. I'm sure that if you'd take a few minutes to look over the book,
you'd immediately recognize that.

To answer your specific question, I don't, in a brief scan, see details
in the book about optimizing the bias for maximum harmonic content of
the multipliers. Most are diode multipliers anyway, with no bias
adjustment. The book covers a very wide range of topics, and the section
on multipliers consists of only a couple of pages of text. There is,
however, a chapter on simple test equipment a homebrewer can build,
including a brief description of a practical spectrum analyzer. Wes did,
incidentally, design and publish such a thing some years ago. I think
it's still available in kit form from Kanga US.

I've also spent a career having to produce real results. But apparently
our approaches differed, because I've found that good paper designs,
often aided by fundamental knowledge gleaned from books, lead to good
hardware results, rather than being an opposing and somehow inferior
method. And they have the advantage of being well understood,
predictable, and repeatable.

Roy Lewallen, W7EL

Avery Fineman wrote:
. . .
Playing with bias on a transistor multiplier stage is fine for optimizing a
multiplication but all it is is play when there's nothing to compare one
bias setting with another as to power output at the desired multiple.
A spectrum analyzer isn't an absolute need, by the way, there's other
ways to measure the harmonic content. Is that in "Experimental
Methods..." published by the ARRL? [I'm pushing work-on-the-bench,
not books, pardon my attitude that has resulted from years of having
to produce hardware results, not paper reports]

Len Anderson
retired (from regular hours) electronic engineering person

Yes, that book is published by the ARRL. Its authors, Wes Hayward,
W7ZOI; Rick Campbell, KK7B; and Bob Larkin, W7PUA have, unlike so many
authors, spent careers doing just what you and I have had to do --
produce hardware results. Of them, I know Wes the best, having been
friends with him for about 30 years. After a stint at Boeing long ago,
Wes was a design engineer in the spectrum analyzer group at Tektronix
for a number of years, where his designs were incorporated in a number
of state-of-the-art spectrum analyzers. He went from there to TriQuint
semiconductor, where he designed many RF components which are in daily
use in probably millions of cell phones and other wireless products. He
recently retired and has been doing some consulting. His publications in
amateur journals, spanning decades, are legendary and many are seminal.
I don't know Rick quite as well, but he's also a very capable and
accomplished engineer (in spite, one might say, of his Ph.D. and period
in academia). For years now, he's also worked as a design engineer at
TriQuint. To get a feel for his approach to solving real problems, check
out the articles he's published over the years in QST on phasing type
direct conversion receivers. Bob I don't know at all, but Wes speaks
very highly of him, and I have absolute confidence in Wes' judgement of
skill.

There's nothing in that book that hasn't been built and tested, and
designed to be repeatable. And everything has been designed by people
who really know what they're doing. This isn't a book of
kluged-it-up-on-the-bench-and-made-one-work-once projects as so many
are. I'm sure that if you'd take a few minutes to look over the book,
you'd immediately recognize that.

To answer your specific question, I don't, in a brief scan, see details
in the book about optimizing the bias for maximum harmonic content of
the multipliers. Most are diode multipliers anyway, with no bias
adjustment. The book covers a very wide range of topics, and the section
on multipliers consists of only a couple of pages of text. There is,
however, a chapter on simple test equipment a homebrewer can build,
including a brief description of a practical spectrum analyzer. Wes did,
incidentally, design and publish such a thing some years ago. I think
it's still available in kit form from Kanga US.

I've also spent a career having to produce real results. But apparently
our approaches differed, because I've found that good paper designs,
often aided by fundamental knowledge gleaned from books, lead to good
hardware results, rather than being an opposing and somehow inferior
method. And they have the advantage of being well understood,
predictable, and repeatable.

Roy Lewallen, W7EL

Roy Lewallen wrote in message ...
... I've found that good paper designs,
often aided by fundamental knowledge gleaned from books, lead to good
hardware results, rather than being an opposing and somehow inferior
method. And they have the advantage of being well understood,
predictable, and repeatable.

Indeed. Occasionaly new not-yet-understood phenomena are discovered
on the bench, but the art benefits greatly from a detailed
understanding of the underlying mechanisms. Coincidently, I was
browsing "Inventions of Opportunity" this afternoon and stumbled
across an article about how in the late 1950's a newly-developed high
speed sampling scope aided in understanding harmonic-generation
mechanisms in diodes, which apparently helped a lot in the development
of step recovery diodes. Before that, apparently there wasn't good
understanding about why some diodes generated lots of harmonics and
others didn't. Step recovery diodes are optimized for fast turn-off
of the reverse recovery, and are used in generating a "comb" of
harmonics. It's not uncommon to pick off the desired harmonic with an
appropriate filter, up to beyond the tenth harmonic. Seems like step
recovery diodes are not in as great favor as they once were, since
there are generally better ways to generate higher order harmonics.

With a little understanding of the spectrum of a non-symmetrical
square (or trapezoid) wave, it's not hard to come very close to an
optimum bias and drive for a given harmonic output in an amplifier
stage. If you do it just by experimentation, you're liable to find a
local optimum that's quite a bit worse than the global optimum. Same
with the output coupling/filtering network.

Cheers,
Tom

Roy Lewallen wrote in message ...
... I've found that good paper designs,
often aided by fundamental knowledge gleaned from books, lead to good
hardware results, rather than being an opposing and somehow inferior
method. And they have the advantage of being well understood,
predictable, and repeatable.

Indeed. Occasionaly new not-yet-understood phenomena are discovered
on the bench, but the art benefits greatly from a detailed
understanding of the underlying mechanisms. Coincidently, I was
browsing "Inventions of Opportunity" this afternoon and stumbled
across an article about how in the late 1950's a newly-developed high
speed sampling scope aided in understanding harmonic-generation
mechanisms in diodes, which apparently helped a lot in the development
of step recovery diodes. Before that, apparently there wasn't good
understanding about why some diodes generated lots of harmonics and
others didn't. Step recovery diodes are optimized for fast turn-off
of the reverse recovery, and are used in generating a "comb" of
harmonics. It's not uncommon to pick off the desired harmonic with an
appropriate filter, up to beyond the tenth harmonic. Seems like step
recovery diodes are not in as great favor as they once were, since
there are generally better ways to generate higher order harmonics.

With a little understanding of the spectrum of a non-symmetrical
square (or trapezoid) wave, it's not hard to come very close to an
optimum bias and drive for a given harmonic output in an amplifier
stage. If you do it just by experimentation, you're liable to find a
local optimum that's quite a bit worse than the global optimum. Same
with the output coupling/filtering network.

Cheers,
Tom

Tom Bruhns wrote:
. . .
. . . Seems like step
recovery diodes are not in as great favor as they once were, since
there are generally better ways to generate higher order harmonics.
. . .

Getting a bit off-topic here, but as of a few years ago, we were using
step recovery diodes to generate the step in high speed TDR systems, and
to generate the strobe for the sampling gate in high speed sampling
scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50
GHz or so), limited primarily by circuitry external to the diodes. SRDs
replaced tunnel diodes in earlier generations of instruments. I've been
out of touch with that class of instruments for a few years now -- do
you know if something has replaced the SRD for generating fast steps, or
just for harmonic generation?

Roy Lewallen, W7EL

Tom Bruhns wrote:
. . .
. . . Seems like step
recovery diodes are not in as great favor as they once were, since
there are generally better ways to generate higher order harmonics.
. . .

Getting a bit off-topic here, but as of a few years ago, we were using
step recovery diodes to generate the step in high speed TDR systems, and
to generate the strobe for the sampling gate in high speed sampling
scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50
GHz or so), limited primarily by circuitry external to the diodes. SRDs
replaced tunnel diodes in earlier generations of instruments. I've been
out of touch with that class of instruments for a few years now -- do
you know if something has replaced the SRD for generating fast steps, or
just for harmonic generation?

Roy Lewallen, W7EL

On Sat, 21 Feb 2004 03:20:07 -0800, Roy Lewallen
wrote:

Tom Bruhns wrote:
. . .
. . . Seems like step
recovery diodes are not in as great favor as they once were, since
there are generally better ways to generate higher order harmonics.
. . .

Getting a bit off-topic here, but as of a few years ago, we were using
step recovery diodes to generate the step in high speed TDR systems, and
to generate the strobe for the sampling gate in high speed sampling
scopes. Rise times were on the order of 7 - 15 ps (bandwidth up to 50
GHz or so), limited primarily by circuitry external to the diodes. SRDs
replaced tunnel diodes in earlier generations of instruments. I've been
out of touch with that class of instruments for a few years now -- do
you know if something has replaced the SRD for generating fast steps, or
just for harmonic generation?

What's a doubler based on the good old 1N4148 good for, top end
frequency-wise?
--

The BBC: Licensed at public expense to spread lies.