Re: [time-nuts] Bye-Bye Crystals
Rick
Yes, the 10811A is a good example of the sort of kludge that is required when one tries to adapt the Colpitts XO to work with an overtone crystal.
However, apart from that, the design is still a lot better than those in most of the ham publications (eg. clamp diodes on JFET gates to limit the amplitude etc).
The E1938A bridged T oscillator along with some of Driscoll's many XO circuits are simpler and more effective.
Bruce
On 15 March 2017 at 06:02 "Richard (Rick) Karlquist" richard@karlquist.com wrote:
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general
oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
Hi,
So what is the « best » design for DIY a high stability OCVXO ?
I am looking after one, needed for an exotic frequency : 5184kHZ
Thx,
Gilles.
Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist richard@karlquist.com a écrit :
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
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and follow the instructions there.
Gilles
What is the required tuning range for the OCVXO?
Bruce
On 15 March 2017 at 20:11 Gilles Clement <clemgill@club-internet.fr> wrote:
Hi,
So what is the « best » design for DIY a high stability OCVXO ?
I am looking after one, needed for an exotic frequency : 5184kHZ
Thx,
Gilles.
Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist <richard@karlquist.com> a écrit :
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
Hi
Where do you plan on getting an OCXO grade crystal at an odd frequency like
that? Much of the performance of a good OCXO is in the crystal. Doing a proper
design on one is a lot of work. You might think that having a design for 5.000000
MHz would give you a good design for 5.000050 MHz. I have empirical evidence that
this isn’t the case. Many years later, I’m still utterly amazed that this is the way things
work in the crystal business ….( = it’s not just a design issue, it’s also a business decision)
More or less the crystal needs to be:
- Cut specifically to have a turn at a temperature that makes sense for your application.
- A “large blank” design (for it’s frequency)
- In a cold weld package (most of the normal crystals are resistance weld)
- Run through a high vacuum / high temperature process
- Be plated with gold rather than something like silver or aluminum (unless it’s at VHF).
- Have a motional capacitance that makes sense for your EFC range ( normally = minimize)
- Preferably be an SC or modified SC cut.
This is for a high stability part. The list does keep going on for a while, but that should
give you a pretty good idea.
Bob
On Mar 15, 2017, at 3:11 AM, Gilles Clement clemgill@club-internet.fr wrote:
Hi,
So what is the « best » design for DIY a high stability OCVXO ?
I am looking after one, needed for an exotic frequency : 5184kHZ
Thx,
Gilles.
Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist richard@karlquist.com a écrit :
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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Le 15 mars 2017 à 08:11, Gilles Clement clemgill@club-internet.fr a écrit :
Hi,
So what is the « best » design for DIY a high stability OCVXO ?
I am looking after one, needed for an exotic frequency : 5184kHZ
Crystals have existed for this frequency. A quick scan of the bay threw up item 252813375636 which is an old radio crystal. If you can figure what you need to drive it, it could be installed into a home-brew oven. How stable you can get it would be the subject of a nice project.
Thx,
Gilles.
Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist richard@karlquist.com a écrit :
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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and follow the instructions there.
"The power of accurate observation is commonly called cynicism by those who have not got it. »
George Bernard Shaw
On 3/15/2017 4:45 AM, Bob Camp wrote:
Hi
Where do you plan on getting an OCXO grade crystal at an odd frequency like
that? Much of the performance of a good OCXO is in the crystal. Doing a proper
design on one is a lot of work. You might think that having a design for 5.000000
MHz would give you a good design for 5.000050 MHz. I have empirical evidence that
this isn’t the case. Many years later, I’m still utterly amazed that this is the way things
work in the crystal business ….( = it’s not just a design issue, it’s also a business decision)
Some 30 years ago when GPS was in its infancy, the hardware utilized
OCXO's at 10.23 MHz. Somehow, HP got suckered into trying to make
modified 10811's that ran at that frequency vs 10 MHz. Jack Kusters
tried to explain to anyone who would listen that this was a major
redesign of the crystal, because he would have to deal with a new
set of anharmonic spurious modes. Although only a 2.3% frequency
change, everything is different. In terms of business decisions,
only something with as much "juice" as GPS could have gotten Jack
to make a custom frequency. As it turned out, a few dozen crystals
were made, and that was the end of it. I managed to snag them
before they were thrown out, in case they might be useful for
something.
The original poster wanted not only an odd frequency (which I don't
recommend for the reasons above) but also wanted to varactor tune
the oscillator. I also don't recommend doing that because of the
difficulty of generating a clean enough DC voltage. Against my
advice, the HP smart clocks were tuned with DAC's driving varactors.
They never really got that to work up to their expectations.
Synthesis is so advanced now, 20 years later, that there is
no reason IMHO to voltage tune an OXCO.
Rick
On 03/15/2017 05:30 PM, Richard (Rick) Karlquist wrote:
On 3/15/2017 4:45 AM, Bob Camp wrote:
Hi
Where do you plan on getting an OCXO grade crystal at an odd frequency
like
that? Much of the performance of a good OCXO is in the crystal. Doing
a proper
design on one is a lot of work. You might think that having a design
for 5.000000
MHz would give you a good design for 5.000050 MHz. I have empirical
evidence that
this isn’t the case. Many years later, I’m still utterly amazed that
this is the way things
work in the crystal business ….( = it’s not just a design issue, it’s
also a business decision)
Some 30 years ago when GPS was in its infancy, the hardware utilized
OCXO's at 10.23 MHz. Somehow, HP got suckered into trying to make
modified 10811's that ran at that frequency vs 10 MHz. Jack Kusters
tried to explain to anyone who would listen that this was a major
redesign of the crystal, because he would have to deal with a new
set of anharmonic spurious modes. Although only a 2.3% frequency
change, everything is different. In terms of business decisions,
only something with as much "juice" as GPS could have gotten Jack
to make a custom frequency. As it turned out, a few dozen crystals
were made, and that was the end of it. I managed to snag them
before they were thrown out, in case they might be useful for
something.
The original poster wanted not only an odd frequency (which I don't
recommend for the reasons above) but also wanted to varactor tune
the oscillator. I also don't recommend doing that because of the
difficulty of generating a clean enough DC voltage. Against my
advice, the HP smart clocks were tuned with DAC's driving varactors.
They never really got that to work up to their expectations.
Synthesis is so advanced now, 20 years later, that there is
no reason IMHO to voltage tune an OXCO.
Agree. Synthesis chips is cheap now and should be sufficiently good.
Also, it may not be a good strategy to zero-beat to the carrier, so such
a frequency may actually be a bad choice. Modern DDS chips allows the
tuning of the LO1 such that different IF frequencies can be tried.
For instance, the RTL-SDR is typically operated in 0 Hz beat, such that
the front-end mixes down to 0 Hz for the carrier and lets the RTL chip
sample the signal. This causes a distinct "blimp" from the 1/f noise.
Shifting the IF from 0 Hz and then let the RTL downconvert after
sampling removes this blimp since the 1/f noise can be brought out of
spectrum. When I dug around, this was available as an option even in GNU
Radio if you only knew it.
This just to illustrate that best result is not always achieved by
bringing it straight on carrier. Sure, it makes the design very very
simple, but has its drawbacks.
Now, the 164 kHz carrier, as sampled by a 48 kHz clock produces a 20 kHz
beat frequency as it wrapps down in the undersampling. To digitally
convert it to DC or lock straight to 20 kHz digitally is fairly trivial.
Similarly, a typical GPS receiver often has the digitized signal offset.
With a more modern view on receiver design and considering the synthesis
tools available, you can play around quite easily and move things around
in interesting ways. For instance, consider that you have an IF filter,
you can with some care sweep the filter and "tune" the LOs to the IF
frequency working best for your needs. We do that in ham receivers to
shift filtering to where it helps from nearby strong signals.
Cheers,
Magnus
Hi,
I have a bunch of 5.184Mhz crystals. Large metallic tanks: HC33U case
Maybe not OCXO grade, but I build a simple oscillator with a 4060 chip
placed in a double oven, and reached 10E-9 short term stability up to 10sec tau.
Not bad, so wondering if I can get better with a more advanced design.
Gilles.
Le 15 mars 2017 à 12:45, Bob Camp kb8tq@n1k.org a écrit :
Hi
Where do you plan on getting an OCXO grade crystal at an odd frequency like
that? Much of the performance of a good OCXO is in the crystal. Doing a proper
design on one is a lot of work. You might think that having a design for 5.000000
MHz would give you a good design for 5.000050 MHz. I have empirical evidence that
this isn’t the case. Many years later, I’m still utterly amazed that this is the way things
work in the crystal business ….( = it’s not just a design issue, it’s also a business decision)
More or less the crystal needs to be:
- Cut specifically to have a turn at a temperature that makes sense for your application.
- A “large blank” design (for it’s frequency)
- In a cold weld package (most of the normal crystals are resistance weld)
- Run through a high vacuum / high temperature process
- Be plated with gold rather than something like silver or aluminum (unless it’s at VHF).
- Have a motional capacitance that makes sense for your EFC range ( normally = minimize)
- Preferably be an SC or modified SC cut.
This is for a high stability part. The list does keep going on for a while, but that should
give you a pretty good idea.
Bob
On Mar 15, 2017, at 3:11 AM, Gilles Clement clemgill@club-internet.fr wrote:
Hi,
So what is the « best » design for DIY a high stability OCVXO ?
I am looking after one, needed for an exotic frequency : 5184kHZ
Thx,
Gilles.
Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist richard@karlquist.com a écrit :
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
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Most likely AT cut fundamental (although there are other possibilities.) designed for operation around room temperature.
Do you have the manufacturer's specs for these?
What is the change in frequency between room temperature and oven temperature?
What is the operating temperature of the inner oven?
Bruce
On 16 March 2017 at 08:36 Gilles Clement <clemgill@club-internet.fr> wrote:
Hi,
I have a bunch of 5.184Mhz crystals. Large metallic tanks: HC33U case
Maybe not OCXO grade, but I build a simple oscillator with a 4060 chip
placed in a double oven, and reached 10E-9 short term stability up to 10sec tau.
Not bad, so wondering if I can get better with a more advanced design.
Gilles.
Le 15 mars 2017 à 12:45, Bob Camp <kb8tq@n1k.org> a écrit :
Hi
Where do you plan on getting an OCXO grade crystal at an odd frequency like
that? Much of the performance of a good OCXO is in the crystal. Doing a proper
design on one is a lot of work. You *might* think that having a design for 5.000000
MHz would give you a good design for 5.000050 MHz. I have empirical evidence that
this isn’t the case. Many years later, I’m still utterly amazed that this is the way things
work in the crystal business ….( = it’s not just a design issue, it’s also a business decision)
More or less the crystal needs to be:
1) Cut specifically to have a turn at a temperature that makes sense for your application.
2) A “large blank” design (for it’s frequency)
3) In a cold weld package (most of the normal crystals are resistance weld)
4) Run through a high vacuum / high temperature process
5) Be plated with gold rather than something like silver or aluminum (unless it’s at VHF).
6) Have a motional capacitance that makes sense for your EFC range ( normally = minimize)
7) Preferably be an SC or modified SC cut.
This is for a high stability part. The list does keep going on for a while, but that should
give you a pretty good idea.
Bob
On Mar 15, 2017, at 3:11 AM, Gilles Clement <clemgill@club-internet.fr> wrote:
Hi,
So what is the « best » design for DIY a high stability OCVXO ?
I am looking after one, needed for an exotic frequency : 5184kHZ
Thx,
Gilles.
Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist <richard@karlquist.com> a écrit :
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
_______________________________________________
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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_______________________________________________
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Hi
By most modern definitions, “high stability” starts around 1x10^-12 (1 ppt) at a tau of 1 second to
10 seconds. There are $20 eBay OCXO’s that run at that level. With a fundamental crystal you
aren’t going to get to that point.
How much EFC range are you after?
How good a CNC setup do you have?
What kind of temperature test setup do you have?
Simply put, the design approach is a “test over temperature / collect data -> optimize” loop.
Without good frequency vs temperature data, you are flying totally blind. Even on a production
design, this is how it’s done. The parts you fiddle are likely to be odd shaped chunks of metal
that fit here or there.
Bob
On Mar 15, 2017, at 3:36 PM, Gilles Clement clemgill@club-internet.fr wrote:
Hi,
I have a bunch of 5.184Mhz crystals. Large metallic tanks: HC33U case
Maybe not OCXO grade, but I build a simple oscillator with a 4060 chip
placed in a double oven, and reached 10E-9 short term stability up to 10sec tau.
Not bad, so wondering if I can get better with a more advanced design.
Gilles.
Le 15 mars 2017 à 12:45, Bob Camp kb8tq@n1k.org a écrit :
Hi
Where do you plan on getting an OCXO grade crystal at an odd frequency like
that? Much of the performance of a good OCXO is in the crystal. Doing a proper
design on one is a lot of work. You might think that having a design for 5.000000
MHz would give you a good design for 5.000050 MHz. I have empirical evidence that
this isn’t the case. Many years later, I’m still utterly amazed that this is the way things
work in the crystal business ….( = it’s not just a design issue, it’s also a business decision)
More or less the crystal needs to be:
- Cut specifically to have a turn at a temperature that makes sense for your application.
- A “large blank” design (for it’s frequency)
- In a cold weld package (most of the normal crystals are resistance weld)
- Run through a high vacuum / high temperature process
- Be plated with gold rather than something like silver or aluminum (unless it’s at VHF).
- Have a motional capacitance that makes sense for your EFC range ( normally = minimize)
- Preferably be an SC or modified SC cut.
This is for a high stability part. The list does keep going on for a while, but that should
give you a pretty good idea.
Bob
On Mar 15, 2017, at 3:11 AM, Gilles Clement clemgill@club-internet.fr wrote:
Hi,
So what is the « best » design for DIY a high stability OCVXO ?
I am looking after one, needed for an exotic frequency : 5184kHZ
Thx,
Gilles.
Le 14 mars 2017 à 18:02, Richard (Rick) Karlquist richard@karlquist.com a écrit :
On 3/14/2017 4:03 AM, Bruce Griffiths wrote:
Looking at oscillator circuits like the HP10811A will give some idea of some of the additional complexity required for a overtone operation. Dissecting a few ocxos may also be helpful. Some start with a 10MHz crystal and a Colpitts sustaining stage and use a 74HC74 or similar to divide the 10Mhz by 2 and drive the output pin. Even when a sinewave output is required often a CMOS inverter drives the output pin via an LC filter.
Bruce
I don't agree here. The 10811 is not a good tutorial for general oscillator design. Because it is SC cut, it has a complicated
mode suppression network across the base emitter junction to
suppress mode B as well as the fundamental.
The E1983A oscillator uses the same crystal (in a low profile
package). You can read my paper about it and see that I
used a very simple bridged tee oscillator circuit. That is
all you need to select the right overtone and mode.
This is the same circuit that I used at Zeta Labs 40 years
ago to design hundreds of custom VCXO's, up to the 9th
overtone. It simply worked every time, unlike various other
designs that were in use at Zeta.
Around 1985, I got a consulting gig at Equatorial Communications
to redesign their 5th overtone VCXO. Only about half of the
crystals would work in their circuit. They had thousands
of "reject" crystals. I just used my old Zeta circuit and
all the crystals started working again.
Equatorial owned the 10 meter dish that you used to see on
your right going south on 237 just before passing over
Central Expressway in Mountain View.
Rick N6RK
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