[time-nuts] Optimal oscillator topology for diffrent frequency range

KA2WEU at aol.com KA2WEU at aol.com
Mon Feb 6 13:14:18 EST 2017


2 points: 
 
First I do not get copies of my own mail... strange  .
 
Second a complete treatment including the results is in 
 
 
http://ieeexplore.ieee.org/document/7546729/ 
These  results are superior  to other publication , and the paper is 
complete.  Probably only very few do a complete literature search. The Disco 
oscillator,  while  applaudable (for its time ) is not used commercially in any 
product  . 
73 de  Ulrich N1UL 
 
 
In a message dated 2/6/2017 11:00:42 A.M. Eastern Standard Time,  
dk4xp at arcor.de writes:

Am 06.02.2017 um  14:08 schrieb Richard (Rick) Karlquist:
> Agreed, for low phase noise  FLOOR, it is imperative to
> take the signal out through the  crystal.  However, for
> close in noise (say ADEV at t=1), the  Driscoll has
> worked well for me.  I have been able to reach  ADEV
> = 10^-11 at 100 MHz at using suitable resonators.
>
>  Rick

But one won't be able to use the power right out of the  crystal
for anything. So it will have to be amplified &  buffered.

If you can do that without lifting the noise floor,  then
you've got to ask yourself one question  :-)

Why don't I  use that little wonder for the sustaining amplifier, too?

And - why do  I divide the precious crystal power between the 2
amplifiers at the  location where it hurts most: where the level is 
smallest?

When you  compare the Driscoll and the Burgoon (sp??) output
coupling through the  crystal, you see it is exactly the same.
One might even apply the current  step up trick from Burgoon.

The current through the drains/collectors  is enforced by the
crystal, operating into a near-short. Off-resonance the  transistor
has complete negative feedback and no gain.

On the output  side of the buffer, losing a dB or two for sustaining
the oscillation does  not hurt.


A thing I do not like about the typical Colpitts is that  it is never
on the series resonance of the crystal. That means that
the  feedback divider is part of the resonance which increases
the number of  critical parts.

In the Driscoll, the sustaining feedback is quite a  wideband thing
and mostly decoupled from the sharp crystal  resonance.


regards, Gerhard, DK4XP



>
> On  2/6/2017 4:35 AM, KA2WEU at aol.com wrote:
>> Not quiet, using the  crystal also as filter gives much better numbers 
>>  ,,,,,
>> 73 de Ulrich N1UL
>>
>> In a message dated  2/6/2017 7:30:33 A.M. Eastern Standard Time,
>> richard at karlquist.com  writes:
>>
>>     I would say the 2 stage  "Driscoll" oscillator is the
>>     way to go.  I  have had good luck with it up to 100 MHz.
>>     The  first stage has the crystal in series with the
>>      emitter, but is otherwise a grounded emitter stage.
>>   The second stage is in cascode as a grounded  base.
>>     The important operating condition is that  only
>>     the second stage limits.  First  publications on
>>     it were in the early 1970's  (search Michael Driscoll).
>>
>>     Rick  Karlquist N6RK  

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