On Sat, 13 Mar 2004 20:35:34 +0000, John Woodgate
wrote:

I read in sci.electronics.design that Reg Edwards
wrote (in
et.com) about 'Extracting the 5th Harmonic', on Sat, 13 Mar 2004:
Then along came Oliver Heaviside who turned the World upside down by
replacing jw with p.

I should probably change my name to Phon .oodgate in his honour. (;-)

It came out as Poodgate in my use of the transform ... ;-)

On 13 Mar 2004 19:00:20 GMT, (Avery Fineman) wrote:

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 -

That IS what I said.

(snip exceptions)

However, all those multiplier types went the way of the dinosaur when
PLLs operating directly at the desired frequency came into being.

That IS what I said.

There isn't any advantage to using those old "exotic" technologies
other than in restoration for nostalgia's sake.

There IS advantage in being aware of analog techniques.

On 13 Mar 2004 19:00:20 GMT, (Avery Fineman) wrote:

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 -

That IS what I said.

(snip exceptions)

However, all those multiplier types went the way of the dinosaur when
PLLs operating directly at the desired frequency came into being.

That IS what I said.

There isn't any advantage to using those old "exotic" technologies
other than in restoration for nostalgia's sake.

There IS advantage in being aware of analog techniques.

On 13 Mar 2004 09:42:37 -0800, (R.Legg) wrote:

budgie wrote in message . ..
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote:

Paul Burridge wrote:



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.

'Tune for smoke' isn't an option for most new products, which have to
be manufactured without hands.

Agreed, but read Michael Black's post below. It's about awareness of other
techniques which help broaden the outlook, rather than starting with a very
narrow view of the solution and trying to make that fit the problem.

onya Michael.

Better to pick a suitable duty cycle (or more likely a conduction time
period in a digital circuit), that has an efficient 5th harmonic
component, including delays, at low power levels.

http://www.wenzel.com/pdffiles/choose.pdf

RL

On 13 Mar 2004 09:42:37 -0800, (R.Legg) wrote:

budgie wrote in message . ..
On Fri, 12 Mar 2004 15:32:23 +0000, Ian Bell wrote:

Paul Burridge wrote:



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.

'Tune for smoke' isn't an option for most new products, which have to
be manufactured without hands.

Agreed, but read Michael Black's post below. It's about awareness of other
techniques which help broaden the outlook, rather than starting with a very
narrow view of the solution and trying to make that fit the problem.

onya Michael.

Better to pick a suitable duty cycle (or more likely a conduction time
period in a digital circuit), that has an efficient 5th harmonic
component, including delays, at low power levels.

http://www.wenzel.com/pdffiles/choose.pdf

RL

Another way of saying that:

If your only tool is a hammer, all problems look like nails.


Jim



-
-Agreed, but read Michael Black's post below. It's about awareness of other
-techniques which help broaden the outlook, rather than starting with a very
-narrow view of the solution and trying to make that fit the problem.



Jim Weir, VP Eng. RST Eng. WX6RST
A&P, CFI, and other good alphabet soup

Another way of saying that:

If your only tool is a hammer, all problems look like nails.


Jim



-
-Agreed, but read Michael Black's post below. It's about awareness of other
-techniques which help broaden the outlook, rather than starting with a very
-narrow view of the solution and trying to make that fit the problem.



Jim Weir, VP Eng. RST Eng. WX6RST
A&P, CFI, and other good alphabet soup

On Sat, 13 Mar 2004 16:15:53 +0000 (UTC), (Ken Smith)
wrote:

In article ,
John Larkin wrote:
[....]
As the duty cycle deviates from 50%, the even harmonics start to
appear, so you need a better filter to keep them out.

Also as you get nearer the 20-80 duty cycle the amplitude of the 5th
harmonic decreases.

Even worse than that - relying on simple reasoning (no maths), the 5th will be
COMPLETELY suppressed when the input's rising and falling edges are spaced so
they correspond in time with the SAME point in the 5th harmonic waveform,
certainly at 20-80, but also at 40-60, 60-40 or 80-20 - a good reason to make
sure that the 50-50 is stable and accurate.
Tony (remove the "_" to reply by email)

On Sat, 13 Mar 2004 16:15:53 +0000 (UTC), (Ken Smith)
wrote:

In article ,
John Larkin wrote:
[....]
As the duty cycle deviates from 50%, the even harmonics start to
appear, so you need a better filter to keep them out.

Also as you get nearer the 20-80 duty cycle the amplitude of the 5th
harmonic decreases.

Even worse than that - relying on simple reasoning (no maths), the 5th will be
COMPLETELY suppressed when the input's rising and falling edges are spaced so
they correspond in time with the SAME point in the 5th harmonic waveform,
certainly at 20-80, but also at 40-60, 60-40 or 80-20 - a good reason to make
sure that the 50-50 is stable and accurate.
Tony (remove the "_" to reply by email)

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
....[snip]....

John L. Reinartz, W1QP, published "A Fundamental-Reinforced Harmonic-
Generating Circuit" in the July, 1937, issue of QST. I don't have a
copy handy, but a followup article "Putting the Harmonic Generator to
Work" in the April, 1938, QST contains this statement:

"It will be remembered that in the harmonic-generator circuit the
crystal oscillator was operated on the crystal frequency only,
and that the following tube was used to generate the even and
odd harmonics up to the 11th and 12th. For our present purpose,
the 8th harmonic is sufficient; that is, 28 Mc. from an 80-meter
crystal...."

Hope this helps.

--Myron.
--
Five boxes preserve our freedoms: soap, ballot, witness, jury, and cartridge
PhD EE (retired). "Barbershop" tenor. CDL(PTXS). W0PBV. (785) 539-4448
NRA Life Member and Certified Instructor (Home Firearm Safety, Rifle, Pistol)