Man with too many clocks.
I am the proverbial man with too many clocks and I don't know what time
it is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO
option. I also
have some TCXO modules. I figured that I would calibrate them against
my Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz TCXO
signals in the other channel and look at the phase relationship. The
TCXO's are
already close enough that I should not be out by more than a fraction of
a waveform.
I understand that I have to deal with the 1 PPS without sawtooth correction.
I expected to see the 10 MHz signal bounce around but not move more than 1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for
a few seconds
then jump a significant portion of the wave. The jump is too much to
be confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
Pete,
Tell us about your trigger: where is it?
Regards,
Antonio/CT1TE
A 2016-11-03 12:20, Peter Reilley escreveu:
I am the proverbial man with too many clocks and I don't know what time it is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option. I also
have some TCXO modules. I figured that I would calibrate them against my Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz TCXO
signals in the other channel and look at the phase relationship. The TCXO's are
already close enough that I should not be out by more than a fraction of a waveform.
I understand that I have to deal with the 1 PPS without sawtooth correction.
I expected to see the 10 MHz signal bounce around but not move more than 1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for a few seconds
then jump a significant portion of the wave. The jump is too much to be confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
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"Danger Wil Robinson...."
There you go good old time nuttery. Pete its bad to start to compare
things. Because then you have questions. That leads to the need for a
better reference.
Around and around it goes.
TCXO's for my 2 cents really tend to introduce variables. Yes better then a
free standing crystal in general. Some of the HPs actually used a true free
standing crystal. 5335 and 5328 as I recall.
By locking all of the counters together you at least limitthat variable to
the source.
Given the cost of GPSDOs that would give you a pretty good arrangement then.
Have fun
Paul
WB8TSL
On Thu, Nov 3, 2016 at 8:20 AM, Peter Reilley preilley_454@comcast.net
wrote:
I am the proverbial man with too many clocks and I don't know what time it
is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.
I also
have some TCXO modules. I figured that I would calibrate them against my
Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz
TCXO
signals in the other channel and look at the phase relationship. The
TCXO's are
already close enough that I should not be out by more than a fraction of a
waveform.
I understand that I have to deal with the 1 PPS without sawtooth
correction.
I expected to see the 10 MHz signal bounce around but not move more than
1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for a
few seconds
then jump a significant portion of the wave. The jump is too much to be
confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
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ailman/listinfo/time-nuts
and follow the instructions there.
There is a problem with you plan. You are looking at the relative phase
of a reference pule and an oscillator, just once. The pulse moves
around, even on a good GPS receive. So what you really have to do is
compare the phase of the oscillator to the AVERAGE phase of the reference.
You have to look at many pulses. This is hard to do what what many
people do is build/buy a GPSDO that sets an oscillator to the running
average GPS PPS pulse then compare the sine wave of the GPS to the
oscillator under test.
Now if working only by eyeball and screwdriver you can still make a GPSDO.
You are the controller. Every second you try and adjust (say) 10% or the
error out of the oscillator and just keep doing this for hours.
Eventually you thing "A $4 micro controller could do this better than I an
and it will not fall asleep after 10 or 20 hours of work." So you spend
the $4 and have a real GPSDO. But you could continue by hand.
Now you have a known-good sine wave use that to compare with your others
But then you start thinking, Is the known good sine wave really good.
How good? Can I measure it? Yes but you will need to build/buy a two
more GPSDOs and run a three-way compare.
Then you see that at least one of the GPSDOs is not as good as the others
so you upgrade it. Then of course one of the other two is now the poorest
performer, so you upgrade it
Then you do all this and likely you forget and have to ask "Why was it I
needed a good clock?"
In theory is is simple: You can't calibrate anything without bringing an
external standard into you lab. GPS is the best one for this use. But
even the GPS PPS is not 100% stable so you need to average tens, or
thousands of them. The number of them you can average depends on the
stability of your oscillator. That's it the rest is just math.
On Thu, Nov 3, 2016 at 5:20 AM, Peter Reilley preilley_454@comcast.net
wrote:
I am the proverbial man with too many clocks and I don't know what time it
is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.
I also
have some TCXO modules. I figured that I would calibrate them against my
Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz
TCXO
signals in the other channel and look at the phase relationship. The
TCXO's are
already close enough that I should not be out by more than a fraction of a
waveform.
I understand that I have to deal with the 1 PPS without sawtooth
correction.
I expected to see the 10 MHz signal bounce around but not move more than
1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for a
few seconds
then jump a significant portion of the wave. The jump is too much to be
confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
time-nuts mailing list -- time-nuts@febo.com
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ailman/listinfo/time-nuts
and follow the instructions there.
--
Chris Albertson
Redondo Beach, California
You can also use your counter to directly measure your GPS receiver's 1PPS,
which ends up being the error of your internal timebase. (plus the error in
your 1PPS)
On Thu, Nov 3, 2016 at 8:20 AM, Peter Reilley preilley_454@comcast.net
wrote:
I am the proverbial man with too many clocks and I don't know what time it
is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.
I also
have some TCXO modules. I figured that I would calibrate them against my
Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz
TCXO
signals in the other channel and look at the phase relationship. The
TCXO's are
already close enough that I should not be out by more than a fraction of a
waveform.
I understand that I have to deal with the 1 PPS without sawtooth
correction.
I expected to see the 10 MHz signal bounce around but not move more than
1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for a
few seconds
then jump a significant portion of the wave. The jump is too much to be
confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
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ailman/listinfo/time-nuts
and follow the instructions there.
I’m going to try and describe my thoughts, but it may not come out as “right” as some others here can do. Still…
One problem you’re going to run into if you go down the road of attempting to PLL one thing to another is that you have to find a balance between phase control and frequency stability.
You’re going to always be reacting to the phase drift of your disciplined device. Your “knob” for doing so is to adjust (probably in steps) the frequency. If your PLL is very “twitchy,” then you’re going to move that knob very quickly and firmly, resulting in very tight phase control, but a frequency that, at least over a short term, will jump around a bit.
By contrast, if you are very reluctant to move the “knob,” then you’re going to move it so slowly that by the time you have a meaningful effect on the phase, the phase will have drifted quite a bit. That said, your movement of the frequency knob will be so slow that the frequency stability would be much better, at least over the short term.
In essence, this is choosing the PLL time constant. How you do so depends on the behavior of your device as well as the stability you desire from the output.
On Nov 3, 2016, at 5:20 AM, Peter Reilley preilley_454@comcast.net wrote:
I am the proverbial man with too many clocks and I don't know what time it is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option. I also
have some TCXO modules. I figured that I would calibrate them against my Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz TCXO
signals in the other channel and look at the phase relationship. The TCXO's are
already close enough that I should not be out by more than a fraction of a waveform.
I understand that I have to deal with the 1 PPS without sawtooth correction.
I expected to see the 10 MHz signal bounce around but not move more than 1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for a few seconds
then jump a significant portion of the wave. The jump is too much to be confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
By the way, the HP5370B has a OCXO, not TCXO. It needs a while to become
stable, but should be quite consistent after that.
On Thu, Nov 3, 2016 at 4:50 PM, Nick Sayer via time-nuts <time-nuts@febo.com
wrote:
I’m going to try and describe my thoughts, but it may not come out as
“right” as some others here can do. Still…
One problem you’re going to run into if you go down the road of attempting
to PLL one thing to another is that you have to find a balance between
phase control and frequency stability.
You’re going to always be reacting to the phase drift of your disciplined
device. Your “knob” for doing so is to adjust (probably in steps) the
frequency. If your PLL is very “twitchy,” then you’re going to move that
knob very quickly and firmly, resulting in very tight phase control, but a
frequency that, at least over a short term, will jump around a bit.
By contrast, if you are very reluctant to move the “knob,” then you’re
going to move it so slowly that by the time you have a meaningful effect on
the phase, the phase will have drifted quite a bit. That said, your
movement of the frequency knob will be so slow that the frequency stability
would be much better, at least over the short term.
In essence, this is choosing the PLL time constant. How you do so depends
on the behavior of your device as well as the stability you desire from the
output.
On Nov 3, 2016, at 5:20 AM, Peter Reilley preilley_454@comcast.net
wrote:
I am the proverbial man with too many clocks and I don't know what time
it is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.
I also
have some TCXO modules. I figured that I would calibrate them against
my Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz
TCXO
signals in the other channel and look at the phase relationship. The
TCXO's are
already close enough that I should not be out by more than a fraction of
a waveform.
I understand that I have to deal with the 1 PPS without sawtooth
correction.
I expected to see the 10 MHz signal bounce around but not move more than
1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for
a few seconds
then jump a significant portion of the wave. The jump is too much to
be confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
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mailman/listinfo/time-nuts
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Yes you are correct. All of the devices I am working with have OCXO's,
it was a type
or a brain short.
Pete.
On 11/3/2016 9:07 PM, Paul Alfille wrote:
By the way, the HP5370B has a OCXO, not TCXO. It needs a while to become
stable, but should be quite consistent after that.
On Thu, Nov 3, 2016 at 4:50 PM, Nick Sayer via time-nuts <time-nuts@febo.com
wrote:
I’m going to try and describe my thoughts, but it may not come out as
“right” as some others here can do. Still…
One problem you’re going to run into if you go down the road of attempting
to PLL one thing to another is that you have to find a balance between
phase control and frequency stability.
You’re going to always be reacting to the phase drift of your disciplined
device. Your “knob” for doing so is to adjust (probably in steps) the
frequency. If your PLL is very “twitchy,” then you’re going to move that
knob very quickly and firmly, resulting in very tight phase control, but a
frequency that, at least over a short term, will jump around a bit.
By contrast, if you are very reluctant to move the “knob,” then you’re
going to move it so slowly that by the time you have a meaningful effect on
the phase, the phase will have drifted quite a bit. That said, your
movement of the frequency knob will be so slow that the frequency stability
would be much better, at least over the short term.
In essence, this is choosing the PLL time constant. How you do so depends
on the behavior of your device as well as the stability you desire from the
output.
On Nov 3, 2016, at 5:20 AM, Peter Reilley preilley_454@comcast.net
wrote:
I am the proverbial man with too many clocks and I don't know what time
it is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO option.
I also
have some TCXO modules. I figured that I would calibrate them against
my Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10 MHz
TCXO
signals in the other channel and look at the phase relationship. The
TCXO's are
already close enough that I should not be out by more than a fraction of
a waveform.
I understand that I have to deal with the 1 PPS without sawtooth
correction.
I expected to see the 10 MHz signal bounce around but not move more than
1/2
of a wave length. Instead I see the 10 MHz waveform appear steady for
a few seconds
then jump a significant portion of the wave. The jump is too much to
be confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
time-nuts mailing list -- time-nuts@febo.com
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mailman/listinfo/time-nuts
and follow the instructions there.
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and follow the instructions there.
I gave up on trying to use the GPS 1 PPS signal to calibrate the 10 MHz
OCXO's that
I have. The reason that others have pointed out is that the
uncorrected 1 PPS
signal from the GPS is has just a little too much a jitter to use it for
calibration
with your eye using a scope. If it were sawtooth corrected then it
would be better
but you really need a GPS disciplined oscillator.
Not to be outdone, I brought out a rubidium oscillator that I had put
away because
it did not appear to work properly. It only put out a 1 PPS signal and
nothing else.
I compared that with the GPS PPS and could get a good comparison on the
scope.
The rubidium drifted about 40 nS over 12 hours. So it seemed to be good.
With that I could adjust the OCXO's in my 5370's. The spec for the HP
5370B with
a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. That
is, it should
take more than 1,000 seconds for one 10 MHz wave to shift by 360
degrees. That
is very hard to do using the screw adjustment in the OCXO. Even the
slightest
movement possible will cause a frequency change greater that is
spec'ed. How
do cal labs do it?
My HP 5370A has a 10544 OCXO which is spec'ed for short term stability of
better than 1 X 10^11 for 1 second. Even better than the 5370B! The
adjustment
screw is much coarser and it is not possible to get any better than a
few seconds for
one cycle phase shift of the 10 MHz OCXO against the standard. It
seems that I can't
get even close to the spec.
These have been running for a few days. It that enough?
Pete.
On 11/3/2016 8:20 AM, Peter Reilley wrote:
I am the proverbial man with too many clocks and I don't know what
time it is.
To correct this situation I have decided to calibrate everything.
I have a HP 5370B, a HP 6370A, and a HP 5328A all with the TCXO
option. I also
have some TCXO modules. I figured that I would calibrate them
against my Trimble
Resolution T GPS receiver.
I put the 1 PPS signal in one channel of my scope and one of the 10
MHz TCXO
signals in the other channel and look at the phase relationship. The
TCXO's are
already close enough that I should not be out by more than a fraction
of a waveform.
I understand that I have to deal with the 1 PPS without sawtooth
correction.
I expected to see the 10 MHz signal bounce around but not move more
than 1/2
of a wave length. Instead I see the 10 MHz waveform appear steady
for a few seconds
then jump a significant portion of the wave. The jump is too much to
be confident
that I have not slipped one cycle.
Can I do what I am trying to do or am I missing something?
Pete.
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
A bit OT, but regarding your Rb, some units needs to be powered thru 2
pins, one is used only for the 10 MHz output buffer, if remember it
correctly. Which is your model number?
Ignacio EB4APL
El 04/11/2016 a las 16:35, Peter Reilley escribió:
I gave up on trying to use the GPS 1 PPS signal to calibrate the 10
MHz OCXO's that
I have. The reason that others have pointed out is that the
uncorrected 1 PPS
signal from the GPS is has just a little too much a jitter to use it
for calibration
with your eye using a scope. If it were sawtooth corrected then it
would be better
but you really need a GPS disciplined oscillator.
Not to be outdone, I brought out a rubidium oscillator that I had put
away because
it did not appear to work properly. It only put out a 1 PPS signal
and nothing else.
I compared that with the GPS PPS and could get a good comparison on
the scope.
The rubidium drifted about 40 nS over 12 hours. So it seemed to be
good.
With that I could adjust the OCXO's in my 5370's. The spec for the
HP 5370B with
a HP 10811 OCXO is better than 1 X 10^-10 RMS for 1 sec average. That
is, it should
take more than 1,000 seconds for one 10 MHz wave to shift by 360
degrees. That
is very hard to do using the screw adjustment in the OCXO. Even the
slightest
movement possible will cause a frequency change greater that is
spec'ed. How
do cal labs do it?
My HP 5370A has a 10544 OCXO which is spec'ed for short term stability of
better than 1 X 10^11 for 1 second. Even better than the 5370B! The
adjustment
screw is much coarser and it is not possible to get any better than a
few seconds for
one cycle phase shift of the 10 MHz OCXO against the standard. It
seems that I can't
get even close to the spec.
These have been running for a few days. It that enough?
Pete.
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