In article , Paul Burridge
writes:

On 13 Mar 2004 07:33:15 -0800, (Tim Shoppa)
wrote:

Fifth harmonic frequency multipliers do exist, but it's usually much
easier to double and triple your way to the final frequency if possible.
(You just discovered this, I think!)

Yeah, but trying to get the 5th is hardly asking for the moon...

In a way, it IS. Fifth harmonic of an infinitely sharp transition
rectangular waveform is still low in energy compared to the
fundamental. Chances are that a single stage using an active
device as a quintupler will NOT be successful, transistor or tube
(valve).

Let's get to some specifics on this problem -

1. Let us know what you are using to determine whether or not
a 5th harmonic exists. The lack of indication may be due to
whatever it is (not a spectrum analyzer) being used.
2. Describe the multiplier stage in more detail and include an
approximate level and impedance/admittance of the RF
source. That would include supply rails and biasing.
3. Describe whatever is being used to select the 5th harmonic
and inhibit the fundamental and other harmonics. There's
lots of energy at many different frequencies floating around
there and you only want one frequency.
4. Review again with us the output drive level requirements so
we can get a handle on that.
5. If you are using an oscilloscope to measure the fundamental
waveform, estimate the actual risetime/falltime based on the
rise/fall times limits of the oscilloscope. That yields some
basic data that can be applied to a Fourier series to determine
the level of 5th harmonic energy you have to work with. [that
will also reveal the approximate frequency limits of the scope]

The lack of even harmonics is typical of push-pull stages ... if you
are messing around with CMOS gates, you might try using a TTL gate
(which pulls low much stronger than it pulls high) or an open collector
TTL gate, both with smmallish (100-200 ohm) pull-up resistors for
doubling.

I've a reasonably fast Schmitt I'm going to stick in there in place of
the 74HC04 before I resort to anything fancy (same pin-out).

Why not do a x3 followed by a x2 to get 17.2 MHz out of 2.866 MHz?

Because I don't have a rock lying about for that fundamental!

Hint: A mixed 2x and 3x = 5x out if filtered to pass that. No lying-
around rock needed. [not an optimum solution]

Note: As already pointed out, a single PLL IC can do the job in the
same PCB footprint.

When frustration hits a peak, it's time to sit back away from the
problem and do an objective review of what is the overall task and
what you've accomplished so far and what you know about certain
circuits fundamentals. General problem descriptions only result in
general solutions without quantitative values needed for a specific
application.

I've found that NON-linear circuits (a multiplier stage is definietly
in the non-linear category) take rather more development time
than a linear circuit. There's lots of different things going on in a
multiplier circuit and those have to be considered for the whole.

Hopefully some supreme being here will spot a problem with the traces
I've now posted...

Try as we might in the depths of our frustrations, supreme beings
tend not to intervene in us humans' petty affairs. :-)

Len Anderson
retired (from regular hours) electronic engineer person

In article , budgie
writes:

On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote:

Paul Burridge wrote:

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. All I can get apart from the fundamental is a strong third
harmonic on 10.32Mhz, regardless of what I tune for.

In RF circles, the 'normal' way to do this would be a simple Class C
amplifier with a collector load tuned to the fifth harmonic. In calls C,
conduction only occurs for a small fraction of a cycle which produces a
correspondingly higher proportion of higher harmonics than a square wave.

I've been waiting for someone to post this. I would only add "The drive
level,
and the bais point, will vary the amount of fifth (or whichever) you will
see."

It's as common as noses in RF, as Ian pointed out. Just look at the average
two-way radio prior to frequency synthesisers. Crystal freqs were multiplied
this way in transmitter chains and for receive injection, although use of
fifth
wasn't especially common because you normally had enough design control to
use the more efficient *2, *3 or *4.

Fifty years ago that was mostly true and multiplier stages rarely went
beyond the 4th harmonic. Two notable exceptions, though -

A circa 1950 design by General Electric for an 1800 MHz radio relay
terminal used a SEPTUPLER via a 2C39 planar triode. [7 x multiplier]
Roughly 260 MHz input following a buffer stage from a 5th overtone
crystal oscillator. Used in both transmitter and receiver panels ("dish-
pan" style, chassis = rack panel) with the receiver septupler driving
the mixer. Fussy to tune but stayed there once tuned.

Another G.E. design of the early 1950s used Locked Oscillators in a
TV broadcast local color subcarrier supply. Locked oscillators operate
on integral multiples of the input and their use was almost extinct back
then. That was deemed necessary in the G.E. design for an 11 x
multiplier, the highest direct multiple I've encountered. A locked
oscillator can also operate as a divider as G.E. did. The 3.58 MHz
crystal could also be phase-locked to a network feed color burst.

However, all those multiplier types went the way of the dinosaur when
PLLs operating directly at the desired frequency came into being.
There isn't any advantage to using those old "exotic" technologies
other than in restoration for nostalgia's sake.

Quintuplers CAN be made, but, so far, Paul hasn't explained
enough specifics about his circuit, or how he is sensing any 5th
harmonic for any of us to get a good handle on a possible aid.

Note: Lacking any spectrum analyzer, a wide-range HF receiver
with an S meter can be an indicator...but such needs to be checked
against a calibrated signal generator for compensation of varying
S meter indication versus input levels. That's what I use for
checking HF levels (Icom R70) and it has been calibrated against
a reasonably-known-level RF source.

Len Anderson
retired (from regular hours) electronic engineer person

In article , budgie
writes:

On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote:

Paul Burridge wrote:

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. All I can get apart from the fundamental is a strong third
harmonic on 10.32Mhz, regardless of what I tune for.

In RF circles, the 'normal' way to do this would be a simple Class C
amplifier with a collector load tuned to the fifth harmonic. In calls C,
conduction only occurs for a small fraction of a cycle which produces a
correspondingly higher proportion of higher harmonics than a square wave.

I've been waiting for someone to post this. I would only add "The drive
level,
and the bais point, will vary the amount of fifth (or whichever) you will
see."

It's as common as noses in RF, as Ian pointed out. Just look at the average
two-way radio prior to frequency synthesisers. Crystal freqs were multiplied
this way in transmitter chains and for receive injection, although use of
fifth
wasn't especially common because you normally had enough design control to
use the more efficient *2, *3 or *4.

Fifty years ago that was mostly true and multiplier stages rarely went
beyond the 4th harmonic. Two notable exceptions, though -

A circa 1950 design by General Electric for an 1800 MHz radio relay
terminal used a SEPTUPLER via a 2C39 planar triode. [7 x multiplier]
Roughly 260 MHz input following a buffer stage from a 5th overtone
crystal oscillator. Used in both transmitter and receiver panels ("dish-
pan" style, chassis = rack panel) with the receiver septupler driving
the mixer. Fussy to tune but stayed there once tuned.

Another G.E. design of the early 1950s used Locked Oscillators in a
TV broadcast local color subcarrier supply. Locked oscillators operate
on integral multiples of the input and their use was almost extinct back
then. That was deemed necessary in the G.E. design for an 11 x
multiplier, the highest direct multiple I've encountered. A locked
oscillator can also operate as a divider as G.E. did. The 3.58 MHz
crystal could also be phase-locked to a network feed color burst.

However, all those multiplier types went the way of the dinosaur when
PLLs operating directly at the desired frequency came into being.
There isn't any advantage to using those old "exotic" technologies
other than in restoration for nostalgia's sake.

Quintuplers CAN be made, but, so far, Paul hasn't explained
enough specifics about his circuit, or how he is sensing any 5th
harmonic for any of us to get a good handle on a possible aid.

Note: Lacking any spectrum analyzer, a wide-range HF receiver
with an S meter can be an indicator...but such needs to be checked
against a calibrated signal generator for compensation of varying
S meter indication versus input levels. That's what I use for
checking HF levels (Icom R70) and it has been calibrated against
a reasonably-known-level RF source.

Len Anderson
retired (from regular hours) electronic engineer person

In addition to what John L. posted about adding in 4th and 6th
harmonics and making it harder to filter, if you have a 40% or 60% (or
20% or 80%) duty cycle, there will be NO fifth harmonic. From what
you've posted, that likely is the crux of your problem.

Cheers,
Tom

Paul Burridge wrote in message . ..
On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:

The 5th harmonic should be only 14dB below the fundamental, although it will
drop fairly quickly as the sides of the input square wave deviate from vertical.

Does the 3.44MHz have a 50% duty cycle?

Not quite, no. Why would that make any difference? I'd have thought
any decent 'squarish wave' of the correct frequency with sharp
rise/fall edges ought to do the trick? It's spewing out the 3rd quite
nicely after all.
How about I post a pic of the sig trace into the multiplier? I'll see
if I can do that a bit later 2day...

In addition to what John L. posted about adding in 4th and 6th
harmonics and making it harder to filter, if you have a 40% or 60% (or
20% or 80%) duty cycle, there will be NO fifth harmonic. From what
you've posted, that likely is the crux of your problem.

Cheers,
Tom

Paul Burridge wrote in message . ..
On Sat, 13 Mar 2004 10:00:52 +1000, Tony wrote:

The 5th harmonic should be only 14dB below the fundamental, although it will
drop fairly quickly as the sides of the input square wave deviate from vertical.

Does the 3.44MHz have a 50% duty cycle?

Not quite, no. Why would that make any difference? I'd have thought
any decent 'squarish wave' of the correct frequency with sharp
rise/fall edges ought to do the trick? It's spewing out the 3rd quite
nicely after all.
How about I post a pic of the sig trace into the multiplier? I'll see
if I can do that a bit later 2day...

On Sat, 13 Mar 2004 17:45:23 +0000 (UTC), "Reg Edwards"
wrote:

Here's the solution. Build a 17.2 one-transistor LC oscillator. It will
easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output
level you like.

Whatever you do don't go for phase locked loops.

Junk your Spice. It tells you nothing you didn't already ought to know. If
you don't know it then you shouldn't be doing the job anyway.

You must have plenty of room on the PCB. But why don't you invest in a 17.2
MHz quartz crystal. They're cheap enough. You've already spent more time
and trouble on research and investigation. Cut your losses.

Hi Reg,

I'm not into cutting my losses and taking the easy way out; I wouldn't
*learn* anything by doing so. This circuit *ought* to work and I hope
to find out why it doesn't and remedy the situation.
I can't build a 17.2Mhz osc. I need to start much lower to multiply up
the 'pullability' of the fundamental to the best part of half a Meg.
Try doing that with a quartz xtal at 17Mhz! Sorry, I mean no offence I
know you're unaware of the background to this project.
BTW, I've built the filter your s/ware designed and it works pretty
much as advertised - bang on 17.2Mhz pass[1] and the third harmonic of
the fundamental at just over 10Mhz is *well* down by a factor of 80X
(sorry, can't be arsed to work out the dB equivalent). The coils I
used to build it were designed with one of your other programs, BTW!
Many thanks indeed. I urge anyone else reading this in r.r.a.hb to
grab Reg's programs whilst they can; they're *extremely* useful and
Reg deserves a vote of thanks from us all for taking the time and
trouble to write them.

[1] Significant spurious pass response at 13.2Mhz for some reason
(probably my use of inappropriate capacitors for the sake of
expediency - Spice didn't predict it) fortunately it just misses the
fourth harmonic!
--

The BBC: Licensed at public expense to spread lies.

On Sat, 13 Mar 2004 17:45:23 +0000 (UTC), "Reg Edwards"
wrote:

Here's the solution. Build a 17.2 one-transistor LC oscillator. It will
easily lock to an injection of the 5th harmonic of 3.44 Mhz at any output
level you like.

Whatever you do don't go for phase locked loops.

Junk your Spice. It tells you nothing you didn't already ought to know. If
you don't know it then you shouldn't be doing the job anyway.

You must have plenty of room on the PCB. But why don't you invest in a 17.2
MHz quartz crystal. They're cheap enough. You've already spent more time
and trouble on research and investigation. Cut your losses.

Hi Reg,

I'm not into cutting my losses and taking the easy way out; I wouldn't
*learn* anything by doing so. This circuit *ought* to work and I hope
to find out why it doesn't and remedy the situation.
I can't build a 17.2Mhz osc. I need to start much lower to multiply up
the 'pullability' of the fundamental to the best part of half a Meg.
Try doing that with a quartz xtal at 17Mhz! Sorry, I mean no offence I
know you're unaware of the background to this project.
BTW, I've built the filter your s/ware designed and it works pretty
much as advertised - bang on 17.2Mhz pass[1] and the third harmonic of
the fundamental at just over 10Mhz is *well* down by a factor of 80X
(sorry, can't be arsed to work out the dB equivalent). The coils I
used to build it were designed with one of your other programs, BTW!
Many thanks indeed. I urge anyone else reading this in r.r.a.hb to
grab Reg's programs whilst they can; they're *extremely* useful and
Reg deserves a vote of thanks from us all for taking the time and
trouble to write them.

[1] Significant spurious pass response at 13.2Mhz for some reason
(probably my use of inappropriate capacitors for the sake of
expediency - Spice didn't predict it) fortunately it just misses the
fourth harmonic!
--

The BBC: Licensed at public expense to spread lies.

On Sat, 13 Mar 2004 10:37:13 -0800, John Larkin
wrote:

On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote:


Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif



That waveform *has* bunches of 5th harmonic. All you need is a
properly functioning bandpass filter to pluck it out.

You must have bloody good eyesight, John! :-)
BTW, can you recommend a sub nS Schmitt inverter that's easily
obtainable?
--

The BBC: Licensed at public expense to spread lies.

On Sat, 13 Mar 2004 10:37:13 -0800, John Larkin
wrote:

On Sat, 13 Mar 2004 16:26:10 +0000, Paul Burridge
wrote:


Okay, I've now tweaked the osc. to get as near to 50% as possible.
Alas, still no sign of any 5th present in the multiplier's output.
Here's a shot of the (fundamental) output from the inverters. I can't
see any real problem with why it shouldn't be good for a reasonable
comb of harmonics, but our experts may know better. BTW, settings were
2V/div. and 0.1uS/div.

http://www.burridge8333.fsbusiness.co.uk/trace.gif



That waveform *has* bunches of 5th harmonic. All you need is a
properly functioning bandpass filter to pluck it out.

You must have bloody good eyesight, John! :-)
BTW, can you recommend a sub nS Schmitt inverter that's easily
obtainable?
--

The BBC: Licensed at public expense to spread lies.

On Sat, 13 Mar 2004 12:50:42 -0600, John Fields
wrote:

That's close enough to 50% that you should have no problem generating
and extracting a fifth harmonic.

Thanks, John. I'd have been surprised if having tweaked it for maximum
50:50 this still wasn't good enough (it's only a tiny bit out now).

If you've got the cap and resistor in series with the base, and no other
circuitry in there, then what you're doing is half-wave rectifying the
square wave in the base-to-emitter diode, and that's what you're seeing,
along with what looks like some AC at the fundamental riding on the
falling peaks and rising valleys of the square wave. The reason you
can't see the fifth harmonic is because it's far enough down that
everything else is so much higher in voltage that it's essentially down
in the mud. If you want the fifth out, you'll have to extract it using
a filter of some sort, the easiest being a series tuned trap or a
parallel tuned tank.

I've lashed up a 17.2Mhz BPF that should do the trick just fine. It'll
be a bit of a fiddle trying to hook it into the existing circuit but
I'll do my best.

Why don't you post your schematic so we can see exactly what you're
doing?

Will do....
--

The BBC: Licensed at public expense to spread lies.