[time-nuts] Data collection from 5115A phase noise test set?

[Anders Wallin]

Hi all,

A 5115A phase noise test set landed in our lab and I am wondering about the
data collection.
It has two telnet ports one for commands and one for phase data.
When issuing "start" on the command-port it starts spitting out
phase-difference values on the data port.

However it seems to me that the phase data alone (REF-DUT phase, in units
of the REF period) is almost useless without knowing the internal workings
of the device.
The phase values are clearly not the true phase difference, which would
quickly accumulate to a huge number with e.g. REF=10MHz and DUT=11MHz. My
understanding is that digital downconversion (DDC) is performed on both REF
and DUT signals, and without knowing the LO frequencies for the DDC the raw
phase data alone is almost useless.

The command prompt does have commands for displaying the internally
calculated ADEV, L(f), frequency-counter readings, etc. and these seem to
show correct and OK values, but there seems to be no way to reproduce e.g.
the ADEV or frequency-counter values/statistics from the raw phase values
on the data port??
Is this correct? Any other experiences with the 5115A or higher end 5120A?

thanks,
Anders
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Re: [time-nuts] Data collection from 5115A phase noise test set?

[Tom Van Baak]

Lucky you! The 5115A has a thousand times better resolution than a hp5370 or 
SR620 counter.

The architecture of the 5110A 5115A and 5120A is described in the manuals. 
These are frequency stability analyzers so the initial phase and frequency 
offsets are not important. What you're seeing is phase difference data *after* 
these initial calibration offsets are removed. This is necessary because the 
unit allows a wide-range of frequencies on either port.

That method also keeps the floating point output from losing accuracy over long 
runs. A count of raw cycles would grow unbounded and you would lose resolution 
as you gained range. So what you're seeing is by design and it doesn't affect 
the phase noise or ADEV plots at all. I'm not sure why you call it "useless".

Note the 5110A has a single-DDS option. When both inputs are nominally the same 
frequency the streaming data is closer to raw phase. Not sure if the 5115/5120 
does also. But either way, none of this matters to ADEV.

Your ADEV plots from raw data should match the ADEV plots on the screen. Watch 
out for bandwidth mismatch.

/tvb


- Original Message - 
From: "Anders Wallin" 
To: "Discussion" 
Sent: Thursday, December 10, 2015 7:20 AM
Subject: [time-nuts] Data collection from 5115A phase noise test set?


> Hi all,
> 
> A 5115A phase noise test set landed in our lab and I am wondering about the
> data collection.
> It has two telnet ports one for commands and one for phase data.
> When issuing "start" on the command-port it starts spitting out
> phase-difference values on the data port.
> 
> However it seems to me that the phase data alone (REF-DUT phase, in units
> of the REF period) is almost useless without knowing the internal workings
> of the device.
> The phase values are clearly not the true phase difference, which would
> quickly accumulate to a huge number with e.g. REF=10MHz and DUT=11MHz. My
> understanding is that digital downconversion (DDC) is performed on both REF
> and DUT signals, and without knowing the LO frequencies for the DDC the raw
> phase data alone is almost useless.
> 
> The command prompt does have commands for displaying the internally
> calculated ADEV, L(f), frequency-counter readings, etc. and these seem to
> show correct and OK values, but there seems to be no way to reproduce e.g.
> the ADEV or frequency-counter values/statistics from the raw phase values
> on the data port??
> Is this correct? Any other experiences with the 5115A or higher end 5120A?
> 
> thanks,
> Anders

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Re: [time-nuts] Phase microstepper designs?

[Brooke Clarke]

Hi Tom:

While I was working at TRW Microwave we were purchased by FEI.  It's my understanding the their key capability was in 
the crystal material in that it produced the cleanest oscillators on the market.


--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
http://www.prc68.com/I/DietNutrition.html

Tom Van Baak wrote:

Are you aware of some redeeming value that phase microsteppers
have that would make us want to investigate them?   Am I
being too harsh on them?  Maybe you can champion them and they
will make a come back :-)

Rick Karlquist N6RK

A phase microstepper is useful with many older Rb and Cs standards (e.g., 5061A 
and 5065A) so that you don't have to touch the C-field. It is also useful with 
a 5071A to improve the time sync/step/steer resolution.

Note that you can also implement a GPSDO with a phase microstepper and this 
allows you to avoid Vref, DAC and EFC. Not all LO have EFC, and even if they 
do, it may be more stable not to use EFC. Plus with a DDS you avoid 
EFC-out-of-range problems.

See also http://leapsecond.com/pages/fe405/ and the links near the bottom. This 
(patented) FEI design avoids the spur issues several of you have been talking 
about: the RF output comes from a low-noise VCXO not the low-drift OCXO+DDS 
itself.

And finally, another very interesting use of a DDS as a sort of microstepper 
phase comparator is:
http://www.ptfinc.com/dsheets/App_35_picoPak.pdf

/tvb
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Re: [time-nuts] Phase microstepper designs?

[Poul-Henning Kamp]

In message <05ea571f-18cd-4046-b520-63f29a892...@n1k.org>, Bob Camp writes:

>> See also http://leapsecond.com/pages/fe405/ and the links near the bottom. 
>> This (patented) FEI design avoids the spur issues several of you have been 
>> talking about: the RF output comes from a low-noise VCXO not the low-drift 
>> OCXO+DDS itself.
>> 
>
>It avoids the far removed spurs. If you have a close in spur, it passes right 
>through the PLL loop and messes up your ADEV. 
>Yes, this really does happen on real gear in the real world …..

Going (almost) 5MHz -> 15 MHz -> 15MHz is just asking for low frequency
trouble.

If I were to design such a product, I would pick the stable OCXO to have
a frequency well removed from the target frequency on as many decimal
digits as possible.

3.1415926535... MHz if I could get away with it.


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] GPSDO and oscillator steering - EFC vs DDS schemes?

[Jim Lux]

(ADEV of 4E-16 at tau of 1000 seconds is a typical state of the art requirement)


…. and has been since the 1970’s when I first started talking with JPL people 
about this :)….


They've gotten a lot smaller and probably draw less power since then.

There's also the testing problem: proving that it has that performance 
is no easy matter.


It might well be that you could build a better one, but that other 
errors in the whole ranging measurement might dominate (movement of the 
antenna on Earth, etc.)


There's a lot of activity centered around making good flight atomic 
clocks with trapped Hg ions.  Those would essentially instantly improve 
over the USO.






All that said, the real question is — can you change the fabrication of the 
crystal in ways that improve it’s stability by
tuning a long way with DDS rather than a short way with reactance (select parts 
plus varicap(s)).



The DDS synthesis thing is nice because you can, to a certain extent, 
control where the spurs and noise are (at the cost of increased logic 
complexity, but that's essentially free, these days), and you can open 
up a trade space on crystals.  You don't have to have certain "special" 
frequencies.



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Re: [time-nuts] Data collection from 5115A phase noise test set?

[John Ackermann N8UR]

There is a gotcha in the TSC phase data... the architecture introduces a 
deliberate phase offset to the phase data so you will always gain (or 
lose) phase over time.  Hook both inputs to the same source, and you'll 
still have a slope in the output data (and the slope and intercept will 
be different on each run).


Thus you *cannot* derive the actual frequency or phase offset from the 
phase data -- it is only useful for stability and phase noise analysis. 
 The TSC people told me this was a feature, not a bug. :-)  If you want 
to get the actual frequency of the DUT, you need to use the fcounter 
function.  And I've never been sure about the averaging used to derive 
the 1/10/100/1000 second values from fcounter, and how best to derive a 
longer-term frequency average from that data.


John

On 12/10/2015 1:44 PM, Tom Van Baak wrote:

Lucky you! The 5115A has a thousand times better resolution than a hp5370 or 
SR620 counter.

The architecture of the 5110A 5115A and 5120A is described in the manuals. 
These are frequency stability analyzers so the initial phase and frequency 
offsets are not important. What you're seeing is phase difference data *after* 
these initial calibration offsets are removed. This is necessary because the 
unit allows a wide-range of frequencies on either port.

That method also keeps the floating point output from losing accuracy over long runs. A 
count of raw cycles would grow unbounded and you would lose resolution as you gained 
range. So what you're seeing is by design and it doesn't affect the phase noise or ADEV 
plots at all. I'm not sure why you call it "useless".

Note the 5110A has a single-DDS option. When both inputs are nominally the same 
frequency the streaming data is closer to raw phase. Not sure if the 5115/5120 
does also. But either way, none of this matters to ADEV.

Your ADEV plots from raw data should match the ADEV plots on the screen. Watch 
out for bandwidth mismatch.

/tvb


- Original Message -
From: "Anders Wallin" 
To: "Discussion" 
Sent: Thursday, December 10, 2015 7:20 AM
Subject: [time-nuts] Data collection from 5115A phase noise test set?



Hi all,

A 5115A phase noise test set landed in our lab and I am wondering about the
data collection.
It has two telnet ports one for commands and one for phase data.
When issuing "start" on the command-port it starts spitting out
phase-difference values on the data port.

However it seems to me that the phase data alone (REF-DUT phase, in units
of the REF period) is almost useless without knowing the internal workings
of the device.
The phase values are clearly not the true phase difference, which would
quickly accumulate to a huge number with e.g. REF=10MHz and DUT=11MHz. My
understanding is that digital downconversion (DDC) is performed on both REF
and DUT signals, and without knowing the LO frequencies for the DDC the raw
phase data alone is almost useless.

The command prompt does have commands for displaying the internally
calculated ADEV, L(f), frequency-counter readings, etc. and these seem to
show correct and OK values, but there seems to be no way to reproduce e.g.
the ADEV or frequency-counter values/statistics from the raw phase values
on the data port??
Is this correct? Any other experiences with the 5115A or higher end 5120A?

thanks,
Anders


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Re: [time-nuts] Data collection from 5115A phase noise test set?

[John Miles]

> Hi all,
> 
> A 5115A phase noise test set landed in our lab and I am wondering about the
> data collection.
> It has two telnet ports one for commands and one for phase data.
> When issuing "start" on the command-port it starts spitting out
> phase-difference values on the data port.
> 
> However it seems to me that the phase data alone (REF-DUT phase, in units
> of the REF period) is almost useless without knowing the internal workings
> of the device.
> The phase values are clearly not the true phase difference, which would
> quickly accumulate to a huge number with e.g. REF=10MHz and DUT=11MHz.
> My
> understanding is that digital downconversion (DDC) is performed on both REF
> and DUT signals, and without knowing the LO frequencies for the DDC the raw
> phase data alone is almost useless.
> 
> The command prompt does have commands for displaying the internally
> calculated ADEV, L(f), frequency-counter readings, etc. and these seem to
> show correct and OK values, but there seems to be no way to reproduce e.g.
> the ADEV or frequency-counter values/statistics from the raw phase values
> on the data port??
> Is this correct? Any other experiences with the 5115A or higher end 5120A?

The shorter-term ADEV values on the 5120A/5125A test sets are mathematically 
backed out of the phase noise data.  They will never perfectly match the ADEV 
values you get from plotting the phase data stream in my experience.  

I don't actually know what they do on the 5115A, though -- since it doesn't do 
cross-correlated PN, there's presumably no reason to derive the short-term ADEV 
plot from the PN data pipeline.  I'd expect the plots to match in that case, 
apart from any errors due to different measurement bandwidths and ADEV bin 
distributions.

It's also true that there will always be an arbitrary phase slope error due to 
the mismatch between the frequency estimate used to tune the internal DDCs and 
the "real" frequency of the incoming data.  Knowledge of the actual DDC core 
frequencies would not be enough to correct for this behavior, because you would 
also need to know how far off they are.  The true frequency offset can't be 
measured ahead of time with perfect certainty, so it has to be estimated, and 
the resulting error will often dominate the slope of the phase-difference graph.

The TimePod and 3120A test sets allow you to specify the input and reference 
frequencies explicitly to obtain a valid phase slope in residual measurements 
and other cases where the exact frequencies are known by the user.  But this is 
something you have to remember to do prior to the measurement, and you still 
don't get a calibrated absolute offset. 

(Also, note that TimeLab can read both phase and PN data from 51xx test sets 
without the need to use a Telnet client.  Not that it helps with this 
particular issue, of course.)

-- john, KE5FX
Miles Design LLC


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[time-nuts] Frequency Electronics, Inc. FE-405B Oscillator Availability

[Skip Withrow]

Hello Time-Nuts,



RDR Electronics has a limited supply of FEI FE-405B OCXO oscillators with
digital  frequency control available.  These are very good crystal
oscillators that are generally BELOW 1x10E-12 from 1 to 1000 seconds (some
approaching a couple of parts in 10E-13).  The mediocre ones are in the
1x10E-11 to 1x10E-12 range for 1 to 1000 seconds (still very good).  In
addition, these units have digital tuning via a serial port that has a
resolution of 1.05x10E-14 (no DACs involved, it’s done with a DDS)!  These
units have a DB-9 connector that is compatible with the FE-5680A and
FE-5650A rubidium units (no LOCK or VCXO signal, of course).



That’s most of the good news, the bad news is that these are 15MHz
oscillators and cannot be changed.  There is a 15MHz PLL and crystal filter
that are the two largest hurdles.  The ovenized oscillator in the unit is
at 5MHz, but it is buried deep below all of the rest of the goodies that
make these interesting.



You can check out lots of FE-405B data on Tom van Baak’s website at
http://www.leapsecond.com/pages/fe405/ .  There are some slides at the end
of all the graphs.  You can check out pictures of the unit at:

http://rdrelectronics.com/skip/dec/fe4051.jpg

http://rdrelectronics.com/skip/dec/fe4052.jpg

http://rdrelectronics.com/skip/dec/fe4053.jpg

http://rdrelectronics.com/skip/dec/fe4054.jpg

http://rdrelectronics.com/skip/dec/fe4055.jpg



The jumping around has been solved.  It is caused by uP temperature
compensation that changes the DDS value based upon the oven heater current.
This input to the uP can be grounded which drives the offset to the max
value and it stays there.  This is absolutely what you would want for a
GPSDO so that you don’t have your control loop fighting the temperature
compensation.  My thinking is that this is what you would want for a
reference oscillator as well, but we have left a few units unmodified.



After running for a while the aging of these units gets down in the
1x10E-12/day range.



In addition, we have set these units so they are reasonably on frequency
(parts in 10E-10) with a 00 00 00 00 control value (same commands as the
FE-5680 and FE-5650).  The range of control values on the FE-405B is F7 33
33 34 to 08 CC CC CC.



We have a VERY limited supply that have been characterized by Corby Dawson
and his H-maser (thanks) and ADEV plot will be sent with the unit.  They
fall into three general groups:

   1. Temperature compensation disabled, great ADEV (1x10E-12 to 1x10E-13
   generally)
   2. Temperature compensation disabled, good ADEV (1x10E-11 to 1x10E-12)
   3. Temperature compensation intact, great ADEV (1x10E-12 to 1x10E-13
   generally)



I would like to offer these up to the time-nuts community.  Asking $200 for
Group 1 and 3 units, $150 for Group 2 units.  Postage to the US is $7.10,
we will ship international – postage is $26.50.  I can send a copy of the
ADEV plot for the unit you would receive via email before you decide to
purchase if desired.  Please send email to s...@rdrelectronics.com.



Sorry for the long post, and the commercial nature (but it is exclusive to
time-nuts at this point).



Thanks,

Skip Withrow

RDR Electronics, Inc.

303-790-1830
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Re: [time-nuts] Frequency Electronics, Inc. FE-405B Oscillator Availability

[Bruce Griffiths]

Its not too difficult to setup a low noise regenerative divider  that will 
produce a 10 Mhz output from a 15MHz input.
Bruce
  


On Friday, 11 December 2015 2:01 PM, Skip Withrow  
wrote:
 

 Hello Time-Nuts,



RDR Electronics has a limited supply of FEI FE-405B OCXO oscillators with
digital  frequency control available.  These are very good crystal
oscillators that are generally BELOW 1x10E-12 from 1 to 1000 seconds (some
approaching a couple of parts in 10E-13).  The mediocre ones are in the
1x10E-11 to 1x10E-12 range for 1 to 1000 seconds (still very good).  In
addition, these units have digital tuning via a serial port that has a
resolution of 1.05x10E-14 (no DACs involved, it’s done with a DDS)!  These
units have a DB-9 connector that is compatible with the FE-5680A and
FE-5650A rubidium units (no LOCK or VCXO signal, of course).



That’s most of the good news, the bad news is that these are 15MHz
oscillators and cannot be changed.  There is a 15MHz PLL and crystal filter
that are the two largest hurdles.  The ovenized oscillator in the unit is
at 5MHz, but it is buried deep below all of the rest of the goodies that
make these interesting.



You can check out lots of FE-405B data on Tom van Baak’s website at
http://www.leapsecond.com/pages/fe405/ .  There are some slides at the end
of all the graphs.  You can check out pictures of the unit at:

http://rdrelectronics.com/skip/dec/fe4051.jpg

http://rdrelectronics.com/skip/dec/fe4052.jpg

http://rdrelectronics.com/skip/dec/fe4053.jpg

http://rdrelectronics.com/skip/dec/fe4054.jpg

http://rdrelectronics.com/skip/dec/fe4055.jpg



The jumping around has been solved.  It is caused by uP temperature
compensation that changes the DDS value based upon the oven heater current.
This input to the uP can be grounded which drives the offset to the max
value and it stays there.  This is absolutely what you would want for a
GPSDO so that you don’t have your control loop fighting the temperature
compensation.  My thinking is that this is what you would want for a
reference oscillator as well, but we have left a few units unmodified.



After running for a while the aging of these units gets down in the
1x10E-12/day range.



In addition, we have set these units so they are reasonably on frequency
(parts in 10E-10) with a 00 00 00 00 control value (same commands as the
FE-5680 and FE-5650).  The range of control values on the FE-405B is F7 33
33 34 to 08 CC CC CC.



We have a VERY limited supply that have been characterized by Corby Dawson
and his H-maser (thanks) and ADEV plot will be sent with the unit.  They
fall into three general groups:

  1. Temperature compensation disabled, great ADEV (1x10E-12 to 1x10E-13
  generally)
  2. Temperature compensation disabled, good ADEV (1x10E-11 to 1x10E-12)
  3. Temperature compensation intact, great ADEV (1x10E-12 to 1x10E-13
  generally)



I would like to offer these up to the time-nuts community.  Asking $200 for
Group 1 and 3 units, $150 for Group 2 units.  Postage to the US is $7.10,
we will ship international – postage is $26.50.  I can send a copy of the
ADEV plot for the unit you would receive via email before you decide to
purchase if desired.  Please send email to s...@rdrelectronics.com.



Sorry for the long post, and the commercial nature (but it is exclusive to
time-nuts at this point).



Thanks,

Skip Withrow

RDR Electronics, Inc.

303-790-1830
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Re: [time-nuts] HP 5065A Start-Up

[John Miles]

> Microphonics.
> 
> What's the norm here?  I see it in the 2nd harmonic level on the panel
> meter.  It runs about 20 normally, but a pretty light tap (with my
> fingernail) anywhere on the instrument can peg the meter for a few
> seconds.  While I had the scope on A8 TP2 / TP3 (showing the off-resonance
> phase shift peak it manifested as bursts of noise) It's hard to localize -
> but I think the RVFR and Synthesizer are the most sensitive.

If your 5065A is like most of the older ones I've seen, it has been upgraded 
with a 10811-60109 OCXO.  If so, there is a spring-loaded shaft extension that 
allows you to access the 10811's calibration trimmer from the panel behind the 
hinged door.  It can be a good idea to remove that hardware, since it can 
otherwise transfer external vibrations to the OCXO.  That probably isn't enough 
to pin the meter but it's still worth checking.

(Be sure to check the ESR of all of the axial tantalum electrolytics on the 
RVFR oven control board, if you haven't already.  A failed oven controller can 
really hose the RVFR.)

-- john, KE5FX
Miles Design LLC

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Re: [time-nuts] HP 5065A Start-Up

[timeok]

Jim,


> Except...
> 
> Microphonics.
> 
> What's the norm here? I see it in the 2nd harmonic level on the panel
> meter. It runs about 20 normally, but a pretty light tap (with my
> fingernail) anywhere on the instrument can peg the meter for a few
> seconds. While I had the scope on A8 TP2 / TP3 (showing the off-resonance
> phase shift peak it manifested as bursts of noise) It's hard to localize -
> but I think the RVFR and Synthesizer are the most sensitive.

20 is the border level of the 2nd harmonic (20-40). After some week of 
continuous operation can happen the signal level  increase otherwise an 
adjustment is necessary.

I had the same experience on some HP5065A revived after a long period of 
inactivity. The microphonics is high during the first few weeks of operation, 
then later recedes.
I could see about a dozen HP5065A that I had in my hands that a reduced 
microphonics  is a feature common to all HP5065A.


Luciano



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> 
> 
> Links:
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Message sent via Atmail Open - http://atmail.org/
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[time-nuts] HP 5065A Start-Up

[Jim/Anna McIntyre]

Turns out there have really just been two major issues so far with this
new-to-me instrument.  As I noted a few days back the pots on the A3
multiplier were intermittent, and twiddling them a bit got the instrument
to lock up.

But it was off by about 77E-10.  The mag field control had no effect.  This
instrument has Option H52.  I've just learned this means the front panel
mag field control is only there to fill up a hole in the panel.  The
control had been re-wired to a spare pin on the rear-panel DC power jack.
All fixed now, and the mag field control works as it should.

I ran through the RF alignment of A3, and all seemed OK there.  Same for
the Phase Detector, Integrator and Loop Gain alignment.  All good.
Except...

Microphonics.

What's the norm here?  I see it in the 2nd harmonic level on the panel
meter.  It runs about 20 normally, but a pretty light tap (with my
fingernail) anywhere on the instrument can peg the meter for a few
seconds.  While I had the scope on A8 TP2 / TP3 (showing the off-resonance
phase shift peak it manifested as bursts of noise) It's hard to localize -
but I think the RVFR and Synthesizer are the most sensitive.
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