10MHz to 25MHz
On Wed, 18 Jan 2017 21:06:04 -0800, you wrote:
On 1/18/2017 6:34 PM, David wrote:
An alternative very simple design I might try is a variation of the
active frequency multiplier where the 5th harmonic is filtered
directly from the output of the digital divide by two stage.
That's a useful trick to reduce the filtering burden. Having said
that, if you need good spectral purity, the filtering is still
going to be very non-trivial. The original poster is obviously
not an expert in filters and will not be successful trying that
approach, except for very low performance design. Even if
you are a filter expert, components are hard to get.
Rick N6RK
I only suggested it because Loren seemed dead set on a harmonic
frequency multiplier. The output from a digital logic gate will
already have a strong 5th harmonic so no extra passive or active
harmonic generating stage is needed. The document I linked discusses
the filtering requirements like notching out the strong 3rd harmonic.
If spectral purity is important, then this is the wrong way to go
about it; it would be better to phase lock a separate crystal
oscillator. In some applications I would also be concerned about the
phase of a narrow bandpass filter changing with temperature.
HI
A lot of your evaluation of the term “better” will depend on your intended use. One of the limits on phase noise
is the thermal noise floor. Because of that, starting at a higher frequency will always give you an edge on broadband
phase noise. ADEV / short term stability is linked to the Q of your resonator. In a quartz crystal, maximum Q is
roughly proportional to frequency. The other limit on Q is blank geometry (size). One other limit is practicality -
is a $250,000 OCXO that is 1 cubic meter in size appropriate for your application? The answer to that one is
universally - NO :) Somewhere along the line of larger size and cost, other technologies make more sense.
So, if better = phase noise floor, 100 MHz is better than 10 MHz. If better = ADEV, 5 MHz in a large package is
likely better than 100 MHz. Indeed these are only two variables. There are many others you could look at.
Lots of fun
Bob
On Jan 19, 2017, at 7:13 AM, Charles Steinmetz csteinmetz@yandex.com wrote:
Chris wrote:
I have always wondered why we build our "standard" with such a low
frequency. Why not a 100MHz GPSDO? Why 10MHz
Quartz crystals work better at lower frequencies, predominantly because they have higher Q. 10MHz was chosen because it is low enough for excellent performance but high enough to be directly useful (since an accident of biology gave us ten fingers, we've created a base-10 world and powers of 10 are favored in almost everything).
In prior times, 5MHz crystals held this position, and before that, 1MHz. There is a good argument even today that the best 2.5MHz or 5MHz crystals are better than the best 10MHz crystals, but not by enough to make 2.5MHz or 5MHz standards popular any longer.
One lonely data point, which proves nothing: My best crystal oscillator is a Symmetricom clone of the double-oven HP 10811s (it came out of an HP GPSDO, so apparently HP at one time used them interchangeably with the 10811). That OCXO uses a 5MHz crystal and a frequency doubler to produce its 10MHz output.
Best Regards,
Charles
On 1/19/2017 5:40 AM, David wrote:
oscillator. In some applications I would also be concerned about the
phase of a narrow bandpass filter changing with temperature.
The 5061 has tuned bandpass filter multipliers which have exactly this
problem. A temperature ramp causes a phase ramp which is the same as a
frequency offset.
Rick N6RK
Bob wrote:
is a $250,000 OCXO that is 1 cubic meter in size appropriate for your application?
The answer to that one is universally - NO
Well, it'll be a lot cheaper when it shows up on ebay. The shipping
might be a killer, though.
;-)
Best regards,
Charles
Wouldn't designing circuitry and PCB's be easier with 10Mhz vs 100Mhz? Maybe not so much now but then.
-=Bryan=-
From: time-nuts time-nuts-bounces@febo.com on behalf of Charles Steinmetz csteinmetz@yandex.com
Sent: January 19, 2017 4:13 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] 10MHz to 25MHz
Chris wrote:
I have always wondered why we build our "standard" with such a low
frequency. Why not a 100MHz GPSDO? Why 10MHz
Quartz crystals work better at lower frequencies, predominantly because
they have higher Q. 10MHz was chosen because it is low enough for
excellent performance but high enough to be directly useful (since an
accident of biology gave us ten fingers, we've created a base-10 world
and powers of 10 are favored in almost everything).
In prior times, 5MHz crystals held this position, and before that, 1MHz.
There is a good argument even today that the best 2.5MHz or 5MHz
crystals are better than the best 10MHz crystals, but not by enough to
make 2.5MHz or 5MHz standards popular any longer.
One lonely data point, which proves nothing: My best crystal oscillator
is a Symmetricom clone of the double-oven HP 10811s (it came out of an
HP GPSDO, so apparently HP at one time used them interchangeably with
the 10811). That OCXO uses a 5MHz crystal and a frequency doubler to
produce its 10MHz output.
Best Regards,
Charles
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Wouldn't crystal drive level be one of the important specifications for far
out phase noise?
On Thu, Jan 19, 2017 at 1:33 PM, Bob Camp kb8tq@n1k.org wrote:
HI
A lot of your evaluation of the term “better” will depend on your intended
use. One of the limits on phase noise
is the thermal noise floor. Because of that, starting at a higher
frequency will always give you an edge on broadband
phase noise. ADEV / short term stability is linked to the Q of your
resonator. In a quartz crystal, maximum Q is
roughly proportional to frequency. The other limit on Q is blank geometry
(size). One other limit is practicality -
is a $250,000 OCXO that is 1 cubic meter in size appropriate for your
application? The answer to that one is
universally - NO :) Somewhere along the line of larger size and cost,
other technologies make more sense.
So, if better = phase noise floor, 100 MHz is better than 10 MHz. If
better = ADEV, 5 MHz in a large package is
likely better than 100 MHz. Indeed these are only two variables. There are
many others you could look at.
Lots of fun
Bob
On Jan 19, 2017, at 7:13 AM, Charles Steinmetz csteinmetz@yandex.com
wrote:
Chris wrote:
I have always wondered why we build our "standard" with such a low
frequency. Why not a 100MHz GPSDO? Why 10MHz
Quartz crystals work better at lower frequencies, predominantly because
they have higher Q. 10MHz was chosen because it is low enough for
excellent performance but high enough to be directly useful (since an
accident of biology gave us ten fingers, we've created a base-10 world and
powers of 10 are favored in almost everything).
In prior times, 5MHz crystals held this position, and before that,
1MHz. There is a good argument even today that the best 2.5MHz or 5MHz
crystals are better than the best 10MHz crystals, but not by enough to make
2.5MHz or 5MHz standards popular any longer.
One lonely data point, which proves nothing: My best crystal oscillator
is a Symmetricom clone of the double-oven HP 10811s (it came out of an HP
GPSDO, so apparently HP at one time used them interchangeably with the
10811). That OCXO uses a 5MHz crystal and a frequency doubler to produce
its 10MHz output.
Best Regards,
Charles
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.
On Jan 19, 2017, at 3:03 PM, Scott Stobbe scott.j.stobbe@gmail.com wrote:
Wouldn't crystal drive level be one of the important specifications for far
out phase noise?
On Thu, Jan 19, 2017 at 1:33 PM, Bob Camp kb8tq@n1k.org wrote:
HI
A lot of your evaluation of the term “better” will depend on your intended
use. One of the limits on phase noise
is the thermal noise floor. Because of that, starting at a higher
frequency will always give you an edge on broadband
phase noise. ADEV / short term stability is linked to the Q of your
resonator. In a quartz crystal, maximum Q is
roughly proportional to frequency. The other limit on Q is blank geometry
(size). One other limit is practicality -
is a $250,000 OCXO that is 1 cubic meter in size appropriate for your
application? The answer to that one is
universally - NO :) Somewhere along the line of larger size and cost,
other technologies make more sense.
So, if better = phase noise floor, 100 MHz is better than 10 MHz. If
better = ADEV, 5 MHz in a large package is
likely better than 100 MHz. Indeed these are only two variables. There are
many others you could look at.
Lots of fun
Bob
On Jan 19, 2017, at 7:13 AM, Charles Steinmetz csteinmetz@yandex.com
wrote:
Chris wrote:
I have always wondered why we build our "standard" with such a low
frequency. Why not a 100MHz GPSDO? Why 10MHz
Quartz crystals work better at lower frequencies, predominantly because
they have higher Q. 10MHz was chosen because it is low enough for
excellent performance but high enough to be directly useful (since an
accident of biology gave us ten fingers, we've created a base-10 world and
powers of 10 are favored in almost everything).
In prior times, 5MHz crystals held this position, and before that,
1MHz. There is a good argument even today that the best 2.5MHz or 5MHz
crystals are better than the best 10MHz crystals, but not by enough to make
2.5MHz or 5MHz standards popular any longer.
One lonely data point, which proves nothing: My best crystal oscillator
is a Symmetricom clone of the double-oven HP 10811s (it came out of an HP
GPSDO, so apparently HP at one time used them interchangeably with the
10811). That OCXO uses a 5MHz crystal and a frequency doubler to produce
its 10MHz output.
Best Regards,
Charles
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To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
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Hi
On Jan 19, 2017, at 3:03 PM, Scott Stobbe scott.j.stobbe@gmail.com wrote:
Wouldn't crystal drive level be one of the important specifications for far
out phase noise?
It would, but you can get the same floor at 10 MHz as you can get at 100 MHz.
Bob
On Thu, Jan 19, 2017 at 1:33 PM, Bob Camp kb8tq@n1k.org wrote:
HI
A lot of your evaluation of the term “better” will depend on your intended
use. One of the limits on phase noise
is the thermal noise floor. Because of that, starting at a higher
frequency will always give you an edge on broadband
phase noise. ADEV / short term stability is linked to the Q of your
resonator. In a quartz crystal, maximum Q is
roughly proportional to frequency. The other limit on Q is blank geometry
(size). One other limit is practicality -
is a $250,000 OCXO that is 1 cubic meter in size appropriate for your
application? The answer to that one is
universally - NO :) Somewhere along the line of larger size and cost,
other technologies make more sense.
So, if better = phase noise floor, 100 MHz is better than 10 MHz. If
better = ADEV, 5 MHz in a large package is
likely better than 100 MHz. Indeed these are only two variables. There are
many others you could look at.
Lots of fun
Bob
On Jan 19, 2017, at 7:13 AM, Charles Steinmetz csteinmetz@yandex.com
wrote:
Chris wrote:
I have always wondered why we build our "standard" with such a low
frequency. Why not a 100MHz GPSDO? Why 10MHz
Quartz crystals work better at lower frequencies, predominantly because
they have higher Q. 10MHz was chosen because it is low enough for
excellent performance but high enough to be directly useful (since an
accident of biology gave us ten fingers, we've created a base-10 world and
powers of 10 are favored in almost everything).
In prior times, 5MHz crystals held this position, and before that,
1MHz. There is a good argument even today that the best 2.5MHz or 5MHz
crystals are better than the best 10MHz crystals, but not by enough to make
2.5MHz or 5MHz standards popular any longer.
One lonely data point, which proves nothing: My best crystal oscillator
is a Symmetricom clone of the double-oven HP 10811s (it came out of an HP
GPSDO, so apparently HP at one time used them interchangeably with the
10811). That OCXO uses a 5MHz crystal and a frequency doubler to produce
its 10MHz output.
Best Regards,
Charles
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/
mailman/listinfo/time-nuts
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Hi
On Jan 19, 2017, at 2:42 PM, Bryan _ bpl521@outlook.com wrote:
Wouldn't designing circuitry and PCB's be easier with 10Mhz vs 100Mhz? Maybe not so much now but then.
Design in general might be a bit easier at the lower frequency “way back when”. I’ve never run into
it as an issue or consideration since the mid 1960’s though.
Bob
-=Bryan=-
From: time-nuts time-nuts-bounces@febo.com on behalf of Charles Steinmetz csteinmetz@yandex.com
Sent: January 19, 2017 4:13 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] 10MHz to 25MHz
Chris wrote:
I have always wondered why we build our "standard" with such a low
frequency. Why not a 100MHz GPSDO? Why 10MHz
Quartz crystals work better at lower frequencies, predominantly because
they have higher Q. 10MHz was chosen because it is low enough for
excellent performance but high enough to be directly useful (since an
accident of biology gave us ten fingers, we've created a base-10 world
and powers of 10 are favored in almost everything).
In prior times, 5MHz crystals held this position, and before that, 1MHz.
There is a good argument even today that the best 2.5MHz or 5MHz
crystals are better than the best 10MHz crystals, but not by enough to
make 2.5MHz or 5MHz standards popular any longer.
One lonely data point, which proves nothing: My best crystal oscillator
is a Symmetricom clone of the double-oven HP 10811s (it came out of an
HP GPSDO, so apparently HP at one time used them interchangeably with
the 10811). That OCXO uses a 5MHz crystal and a frequency doubler to
produce its 10MHz output.
Best Regards,
Charles
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
time-nuts Info Page - American Febo Enterpriseshttps://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
www.febo.com
time-nuts is a low volume, high SNR list for the discussion of precise time and frequency measurement and related topics. To see the collection of prior postings to ...
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
Is there any reason why you wouldn't be able to run the same drive level on
say the fifth overtone versus the fundamental? I would guess at 100 MHz it
may be 3rd or 5th, or are they fundamental?
The comments one drivelevel are simply based on snr, larger signal with
same noise, better snr
On Thu, Jan 19, 2017 at 7:06 PM Bob Camp kb8tq@n1k.org wrote:
Hi
On Jan 19, 2017, at 3:03 PM, Scott Stobbe scott.j.stobbe@gmail.com
wrote:
Wouldn't crystal drive level be one of the important specifications for
far
out phase noise?
It would, but you can get the same floor at 10 MHz as you can get at 100
MHz.
Bob
On Thu, Jan 19, 2017 at 1:33 PM, Bob Camp kb8tq@n1k.org wrote:
HI
A lot of your evaluation of the term “better” will depend on your
intended
use. One of the limits on phase noise
is the thermal noise floor. Because of that, starting at a higher
frequency will always give you an edge on broadband
phase noise. ADEV / short term stability is linked to the Q of your
resonator. In a quartz crystal, maximum Q is
roughly proportional to frequency. The other limit on Q is blank
geometry
(size). One other limit is practicality -
is a $250,000 OCXO that is 1 cubic meter in size appropriate for your
application? The answer to that one is
universally - NO :) Somewhere along the line of larger size and cost,
other technologies make more sense.
So, if better = phase noise floor, 100 MHz is better than 10 MHz. If
better = ADEV, 5 MHz in a large package is
likely better than 100 MHz. Indeed these are only two variables. There
are
many others you could look at.
Lots of fun
Bob
On Jan 19, 2017, at 7:13 AM, Charles Steinmetz csteinmetz@yandex.com
wrote:
Chris wrote:
I have always wondered why we build our "standard" with such a low
frequency. Why not a 100MHz GPSDO? Why 10MHz
Quartz crystals work better at lower frequencies, predominantly because
they have higher Q. 10MHz was chosen because it is low enough for
excellent performance but high enough to be directly useful (since an
accident of biology gave us ten fingers, we've created a base-10 world
and
powers of 10 are favored in almost everything).
In prior times, 5MHz crystals held this position, and before that,
1MHz. There is a good argument even today that the best 2.5MHz or 5MHz
crystals are better than the best 10MHz crystals, but not by enough to
make
2.5MHz or 5MHz standards popular any longer.
One lonely data point, which proves nothing: My best crystal
oscillator
is a Symmetricom clone of the double-oven HP 10811s (it came out of an
HP
GPSDO, so apparently HP at one time used them interchangeably with the
10811). That OCXO uses a 5MHz crystal and a frequency doubler to
produce
its 10MHz output.
Best Regards,
Charles
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.
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