You're probably thinking of the oscillator that Marv Frerking
called a "grounded-base oscillator". I have seen it called other
names as well. Basically, what you do is first build an LC
(ie no xtal) Colpitts oscillator and tune it to the crystal frequency
you want to eventually use. Then insert a resistor of a few
dozen ohms in series with the emitter. Now, readjust the feedback
capacitors on the oscillator to get it to oscillate OK with the resistor.
Finally, replace the resistor with a series resonant crystal.
It will be forced to oscillate at the frequency of the original LC
oscillator, since there is no gain anywhere else. Thus you can
design for either the fundamental or a specific harmonic and like
you say it can't flip to a different overtone. For more details,
read one of Frerking's books.

Rick N6RK

"Paul Burridge" wrote in message
news

Hi,

I'm trying to track down the name for a certain type of oscillator
which I dimly recall seeing in an old book called Radio & Line
Transmission that I bought and lost over 3 decades ago.
In simple terms, it has a crystal in the base/emitter circuit and a
C/L tank for the resonant frequency of the crystal in the collector
circuit. In this way it can't flip into an overtone since it only has
gain at the crystal's fundamental. Anyone know the name for it?

Thanks,

p.

--

The BBC: Licensed at public expense to spread lies.

You're probably thinking of the oscillator that Marv Frerking
called a "grounded-base oscillator".

Alternatively, take a look at the Butler design by John Stephensen in
November/December 1999 QEX. He explains clearly why folks ever had problems
with Butlers and better yet, how to cure them. I've used this circuit
(without the Varactor tuning) on 9th overtone oscillators using hound dog
crystals.

W4ZCB

On Tue, 24 Feb 2004 16:02:23 GMT, the renowned "Harold E. Johnson"
wrote:


You're probably thinking of the oscillator that Marv Frerking
called a "grounded-base oscillator".

Alternatively, take a look at the Butler design by John Stephensen in
November/December 1999 QEX. He explains clearly why folks ever had problems
with Butlers and better yet, how to cure them. I've used this circuit
(without the Varactor tuning) on 9th overtone oscillators using hound dog
crystals.
W4ZCB

What's a "hound dog crystal"?

How to deal with butlers:
http://etext.library.adelaide.edu.au...chapter41.html


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com

What's a "hound dog crystal"?

How to deal with butlers:
http://etext.library.adelaide.edu.au...chapter41.html


Best regards,
Spehro Pefhany



Thanks Spehro. Delightful! I wondered what it had to do with things until
down the page a bit.

Sorry for the lack of definition, I was referring to crystals not
specifically treated to enhance overtone operation. When a manufacturer
makes a crystal for overtone use, he/she treats it to suppress spurious
responses close by the desired overtone so the crystal "likes" to operate
properly. An untreated crystal often will have those responses and oscillate
on one or more of them instead of the desired frequency unless the feedback
and tuned circuit are carefully managed to ignore them. The higher
impedance of Stephensens schematic make that a bit easier to do.

Regards

W4ZCB

On Tue, 24 Feb 2004 17:45:51 GMT, "Harold E. Johnson"
wrote:

Sorry for the lack of definition, I was referring to crystals not
specifically treated to enhance overtone operation. When a manufacturer
makes a crystal for overtone use, he/she treats it to suppress spurious
responses close by the desired overtone so the crystal "likes" to operate
properly. An untreated crystal often will have those responses and oscillate
on one or more of them instead of the desired frequency unless the feedback
and tuned circuit are carefully managed to ignore them.

The following link is worth checking out as an overview....

http://www.icmfg.com/crystaloscillatordata.html
--

The BBC: Licensed at public expense to spread lies.

In article j5M_b.5335$AL.133044@attbi_s03, Harold E. Johnson
writes


What's a "hound dog crystal"?

How to deal with butlers:
http://etext.library.adelaide.edu.au...chapter41.html


Best regards,
Spehro Pefhany



Thanks Spehro. Delightful! I wondered what it had to do with things until
down the page a bit.

Sorry for the lack of definition, I was referring to crystals not
specifically treated to enhance overtone operation. When a manufacturer
makes a crystal for overtone use, he/she treats it to suppress spurious
responses close by the desired overtone so the crystal "likes" to
operate
properly. An untreated crystal often will have those responses and
oscillate
on one or more of them instead of the desired frequency unless the
feedback
and tuned circuit are carefully managed to ignore them. The higher
impedance of Stephensens schematic make that a bit easier to do.


The special techniques were as follows:
Optimise the plating thickness for the overtone and also the electrode
diameter.
Shear mode crystals have a controlled relationship between the resonant
frequency under the electrode and the frequency away from the
electroded region.

Also higher overtones are better polished and more sensitive to
parallelism.

Overtones pull less approx pulling of fundimental/overtone number
squared.



--
ddwyer

On Tue, 24 Feb 2004 17:45:51 GMT, "Harold E. Johnson"
wrote:

Sorry for the lack of definition, I was referring to crystals not
specifically treated to enhance overtone operation. When a manufacturer
makes a crystal for overtone use, he/she treats it to suppress spurious
responses close by the desired overtone so the crystal "likes" to operate
properly. An untreated crystal often will have those responses and oscillate
on one or more of them instead of the desired frequency unless the feedback
and tuned circuit are carefully managed to ignore them.

The following link is worth checking out as an overview....

http://www.icmfg.com/crystaloscillatordata.html
--

The BBC: Licensed at public expense to spread lies.

In article j5M_b.5335$AL.133044@attbi_s03, Harold E. Johnson
writes


What's a "hound dog crystal"?

How to deal with butlers:
http://etext.library.adelaide.edu.au...chapter41.html


Best regards,
Spehro Pefhany



Thanks Spehro. Delightful! I wondered what it had to do with things until
down the page a bit.

Sorry for the lack of definition, I was referring to crystals not
specifically treated to enhance overtone operation. When a manufacturer
makes a crystal for overtone use, he/she treats it to suppress spurious
responses close by the desired overtone so the crystal "likes" to
operate
properly. An untreated crystal often will have those responses and
oscillate
on one or more of them instead of the desired frequency unless the
feedback
and tuned circuit are carefully managed to ignore them. The higher
impedance of Stephensens schematic make that a bit easier to do.


The special techniques were as follows:
Optimise the plating thickness for the overtone and also the electrode
diameter.
Shear mode crystals have a controlled relationship between the resonant
frequency under the electrode and the frequency away from the
electroded region.

Also higher overtones are better polished and more sensitive to
parallelism.

Overtones pull less approx pulling of fundimental/overtone number
squared.



--
ddwyer

What's a "hound dog crystal"?

How to deal with butlers:
http://etext.library.adelaide.edu.au...chapter41.html


Best regards,
Spehro Pefhany



Thanks Spehro. Delightful! I wondered what it had to do with things until
down the page a bit.

Sorry for the lack of definition, I was referring to crystals not
specifically treated to enhance overtone operation. When a manufacturer
makes a crystal for overtone use, he/she treats it to suppress spurious
responses close by the desired overtone so the crystal "likes" to operate
properly. An untreated crystal often will have those responses and oscillate
on one or more of them instead of the desired frequency unless the feedback
and tuned circuit are carefully managed to ignore them. The higher
impedance of Stephensens schematic make that a bit easier to do.

Regards

W4ZCB

On Tue, 24 Feb 2004 16:02:23 GMT, the renowned "Harold E. Johnson"
wrote:


You're probably thinking of the oscillator that Marv Frerking
called a "grounded-base oscillator".

Alternatively, take a look at the Butler design by John Stephensen in
November/December 1999 QEX. He explains clearly why folks ever had problems
with Butlers and better yet, how to cure them. I've used this circuit
(without the Varactor tuning) on 9th overtone oscillators using hound dog
crystals.
W4ZCB

What's a "hound dog crystal"?

How to deal with butlers:
http://etext.library.adelaide.edu.au...chapter41.html


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com