Paul Burridge wrote in message . ..
Hi all,

Is there some black magic required to get higher order harmonics out
of an oscillator?
I'm only trying to get 17.2Mhz out of a 3.44Mhz source and am thus far
failing spectacularly. I've tried everything I can think of so far to
no avail.

C2's small size (3.3pF)is attenuating any 5th harmonic current by 6db
into
Q2's base biasing network, in both posted versions.

Biasing the first stage as classC in the second revision is a pretty
drastic change from the previous class A revision (100mW). Don't you
believe in tiny steps?

By the way, when you post a waveform where traces are only identified
by node numbers, when the schematic provided is an image only, there's
no way we can know where the traces originate, unless you tell us.

RL

On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this:


I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Send 'em both!

I'm still working on an LTspice version of a varactor multiplier using
the base-emitter junction of a class C amp as the varactor. Basically using an
"idler" tank or tanks to augment the fifth harmonic.

The other idea is to make a doubler and a trippler fed from the
fundamental and then feed them into a mixer to get the fifth. If the doubler
and trippler are active (class C) stages, you should get as many db out at the
higher frequency as you put in at the fundamental. The mixer can have gain too.
Three transistors, three tuned circuits, and Bob's yer uncle.

Jim

On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this:


I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Send 'em both!

I'm still working on an LTspice version of a varactor multiplier using
the base-emitter junction of a class C amp as the varactor. Basically using an
"idler" tank or tanks to augment the fifth harmonic.

The other idea is to make a doubler and a trippler fed from the
fundamental and then feed them into a mixer to get the fifth. If the doubler
and trippler are active (class C) stages, you should get as many db out at the
higher frequency as you put in at the fundamental. The mixer can have gain too.
Three transistors, three tuned circuits, and Bob's yer uncle.

Jim

On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote:

On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this:


I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Send 'em both!

I'm still working on an LTspice version of a varactor multiplier using
the base-emitter junction of a class C amp as the varactor. Basically using an
"idler" tank or tanks to augment the fifth harmonic.

The other idea is to make a doubler and a trippler fed from the
fundamental and then feed them into a mixer to get the fifth. If the doubler
and trippler are active (class C) stages, you should get as many db out at the
higher frequency as you put in at the fundamental. The mixer can have gain too.
Three transistors, three tuned circuits, and Bob's yer uncle.

Jim


Why not just bandpass filter the 5th from the square wave? Too simple?


John

On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote:

On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this:


I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Send 'em both!

I'm still working on an LTspice version of a varactor multiplier using
the base-emitter junction of a class C amp as the varactor. Basically using an
"idler" tank or tanks to augment the fifth harmonic.

The other idea is to make a doubler and a trippler fed from the
fundamental and then feed them into a mixer to get the fifth. If the doubler
and trippler are active (class C) stages, you should get as many db out at the
higher frequency as you put in at the fundamental. The mixer can have gain too.
Three transistors, three tuned circuits, and Bob's yer uncle.

Jim


Why not just bandpass filter the 5th from the square wave? Too simple?


John

On Sun, 14 Mar 2004 13:14:40 +0000, Paul Burridge wrote:

On Sat, 13 Mar 2004 20:23:45 -0500, Active8
wrote:

Just a rough guess, since your calling on supreme beings...

The post is still vacant as yet...
:-)

That input cap... I take it the input source is a reasonable
estimate of your square wave... if the time constant of that input
RC net isn't right, it'll be a differentiator, and turn your square
wave into pulses coincident with the rising and falling edges. Your
scope trace suggested otherwise, but IIRC, at that tin=me you were
using the filter at the input to the mult., xo things have changed.

There's been no filtering (other than the selective properties of the
tank circuits) whatsoever employed thus far.

It doesn't look like you're biased in Class C. All the mults I've
seen are Class C biased with the tuned circuit on the collector. And
remember, when you're doing this later for some other purpose, in
Class C, the transistors Vceo - reverse breakdown - must be at least
twice the supply voltage.

Yup, perfectly correct. I must admit that going the class C route with
the tank tuned to the required harmonic was the way I was 'brought up'
as it were. Class C typically generates lots of harmonics as you
obviously know. This multiplier seems to be operating in class A,
which I admit is odd given its high linearity. But I didn't design the
multiplying stage you see here, but the guy who did is an RF expert so
I don't argue. :-)

But you've just given me an idea: maybe I should increase the value of
the 82 ohm base-ground resistor to increase drive signal level and tip
the stage into class C. Worth a try?

Nah. With a *sine* input, you'd bias it so it only conducts for less
than 180 degrees of the fundamental's cycle - keep the trans *out*
of conduction for the most part. Now that I think of it, yer using a
square wave and should have the stinkin' harmonic already, duh. What
was I thinkin'? I still wonder what that input cap is doing to the
edges. The trace you posted indicates it *might* be ok if nothing
changed.

Just for grins, get rid of that input cap and do whatever with the
bias to allow you to DC couple the multiplier. That's pretty class
C'ish assuming a 0 - 5V square wave. Don't fry your b-e junction.
Something's wiping out your 5th, so lets get that input RC outta
there.
--
Best Regards,
Mike

On Sun, 14 Mar 2004 13:14:40 +0000, Paul Burridge wrote:

On Sat, 13 Mar 2004 20:23:45 -0500, Active8
wrote:

Just a rough guess, since your calling on supreme beings...

The post is still vacant as yet...
:-)

That input cap... I take it the input source is a reasonable
estimate of your square wave... if the time constant of that input
RC net isn't right, it'll be a differentiator, and turn your square
wave into pulses coincident with the rising and falling edges. Your
scope trace suggested otherwise, but IIRC, at that tin=me you were
using the filter at the input to the mult., xo things have changed.

There's been no filtering (other than the selective properties of the
tank circuits) whatsoever employed thus far.

It doesn't look like you're biased in Class C. All the mults I've
seen are Class C biased with the tuned circuit on the collector. And
remember, when you're doing this later for some other purpose, in
Class C, the transistors Vceo - reverse breakdown - must be at least
twice the supply voltage.

Yup, perfectly correct. I must admit that going the class C route with
the tank tuned to the required harmonic was the way I was 'brought up'
as it were. Class C typically generates lots of harmonics as you
obviously know. This multiplier seems to be operating in class A,
which I admit is odd given its high linearity. But I didn't design the
multiplying stage you see here, but the guy who did is an RF expert so
I don't argue. :-)

But you've just given me an idea: maybe I should increase the value of
the 82 ohm base-ground resistor to increase drive signal level and tip
the stage into class C. Worth a try?

Nah. With a *sine* input, you'd bias it so it only conducts for less
than 180 degrees of the fundamental's cycle - keep the trans *out*
of conduction for the most part. Now that I think of it, yer using a
square wave and should have the stinkin' harmonic already, duh. What
was I thinkin'? I still wonder what that input cap is doing to the
edges. The trace you posted indicates it *might* be ok if nothing
changed.

Just for grins, get rid of that input cap and do whatever with the
bias to allow you to DC couple the multiplier. That's pretty class
C'ish assuming a 0 - 5V square wave. Don't fry your b-e junction.
Something's wiping out your 5th, so lets get that input RC outta
there.
--
Best Regards,
Mike

On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote:

On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this:


I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Send 'em both!

I'm still working on an LTspice version of a varactor multiplier using
the base-emitter junction of a class C amp as the varactor. Basically using an
"idler" tank or tanks to augment the fifth harmonic.

The other idea is to make a doubler and a trippler fed from the
fundamental and then feed them into a mixer to get the fifth. If the doubler
and trippler are active (class C) stages, you should get as many db out at the
higher frequency as you put in at the fundamental. The mixer can have gain too.
Three transistors, three tuned circuits, and Bob's yer uncle.

Jim, please remember the fundamental has to be in the order of
~3.5Mhz.
--

The BBC: Licensed at public expense to spread lies.

On Sun, 14 Mar 2004 19:51:50 GMT, James Meyer
wrote:

On Sat, 13 Mar 2004 11:50:12 +0000, Paul Burridge
posted this:


I have at least one suggestion, but I need to know whether to send an
LTspice netlist or a gif.

Send 'em both!

I'm still working on an LTspice version of a varactor multiplier using
the base-emitter junction of a class C amp as the varactor. Basically using an
"idler" tank or tanks to augment the fifth harmonic.

The other idea is to make a doubler and a trippler fed from the
fundamental and then feed them into a mixer to get the fifth. If the doubler
and trippler are active (class C) stages, you should get as many db out at the
higher frequency as you put in at the fundamental. The mixer can have gain too.
Three transistors, three tuned circuits, and Bob's yer uncle.

Jim, please remember the fundamental has to be in the order of
~3.5Mhz.
--

The BBC: Licensed at public expense to spread lies.

On Sun, 14 Mar 2004 12:04:18 -0800, John Larkin
wrote:


Why not just bandpass filter the 5th from the square wave? Too simple?

I suggested this a while ago, but no one seemed very keen on that
solution for some reason. Pity, as it does seem to Spice very well. A
5/6V TTL level square wave winds up as around .5 of a volt of 5th
harmonic, post-filtering. Not bad!
--

The BBC: Licensed at public expense to spread lies.