Re: [time-nuts] Thermal impact on OCXO

[Scott Stobbe]

On Mon, Nov 7, 2016 at 10:34 AM, Scott Stobbe 
wrote:

> Here is a sample data point taken from http://tycho.usno.navy.mil/ptt
> i/1987papers/Vol%2019_16.pdf; the first that showed up on a google search.
>
>  Year   Aging [PPB]  dF/dt [PPT/Day]
> 1   180.51   63.884
> 2   196.6531.93
> 5  218   12.769
> 9   231.69   7.0934
>10   234.156.384
>25255.5   2.5535
>
> If you have a set of coefficients you believe to be representative of your
> OCXO, we can give those a go.
>
>
I thought I would come back to this sample data point and see what the
impact of using a 1st order estimate for the log function would entail.

The coefficients supplied in the paper are the following:
 A1 = 0.0233;
 A2 = 4.4583;
 A3 = 0.0082;

F =  A1*ln( A2*x +1 ) + A3;  where x is time in days

 Fdot = (A1*A2)/(A2*x +1)

 Fdotdot = -(A1*A2^2)/(A2*x +1)^2

When x is large, the derivatives are approximately:

 Fdot ~= A1/x

 Fdotdot ~= -A1/x^2

It's worth noting that, just as it is visually apparent from the graph, the
aging becomes more linear as time progresses, the second, third, ...,
derivatives drop off faster than the first.

A first order taylor series of the aging would be,

 T1(x, xo) = A3 + A1*ln(A2*xo + 1) +  (A1*A2)(x - xo)/(A2*xo +1) + O(
(x-xo)^2 )

The remainder (error) term for a 1st order taylor series of F would be:
  R(x) = Fdotdot(c) * ((x-xo)^2)/(2!);  where c is some value between x
and xo.

So, take for example, forward projecting the drift one day after the 365th
day using a first order model,
 xo = 365

 Fdot(365) =  63.796 PPT/day, alternatively the approximate derivative
is: 63.836 PPT/day

 |R(366)| =  0.087339 PPT (more than likely, this is no where near 1
DAC LSB on the EFC line)

More than likely you wouldn't try to project 7 days out, but considering
only the generalized effects of aging, the error would be:

 |R(372)| = 4.282 PPT (So on the 7th day, a 1st order model starts to
degrade into a few DAC LSB)

In the case of forward projecting aging for one day, using a 1st order
model versus the full logarithmic model, would likely be a discrepancy of
less than one dac LSB.
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Re: [time-nuts] Do the HP 5334A & 5335A counter/timers take the same oven oscillator?

[Richard (Rick) Karlquist]

In general, any 10811 with an edge card type connector
in interchangeable in any instrument, in terms of basic
functionality.  The only differences
are that various part numbers in the 10811 family are
selected for certain critical specs.  Certainly, between
the 5334 and 5335, they are interchangeable.  OTOH,
an instrument like the 8662A might not meet phase noise
without the "official" version of 10811.

A 10811 also must work in any 10544 socket, although the
reverse isn't necessarily true.

The 5334A (as opposed to the 5334B that I was the project
manager on) has a poorly regulated power supply that causes the oven
power voltage to drop to only +12V during warmup, which
is supposedly below the +15V minimum and the +20V nominal.
It turns out that +12V is sufficient to cause the oven
to warm up.  It is not sufficient to operate the oven
well in a steady state.  However, once the oven current
cuts back, the power supply voltage goes back up to over
15 volts so everything works.  I fixed this problem in
the 5334B.  I don't know if the 5335 has a similar problem.

Rick
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Re: [time-nuts] GPS Model ?

[Chris Albertson]

I've got some older Oncore stuff too.   The specs sound dated but are
orders of magnitude better than needed for NTP servers.   It is the kind of
thing you turn on then it just runs for years.  Get a good outdoor antenna.

That said, last time, a few months ago when I was looking for an under $10
receiver I ended up with a U-Blox 6 for about $7 shipped.  It outperforms
the Oncore in every way

On Sun, Nov 13, 2016 at 3:06 PM, Art Sepin  wrote:

> Mitch,
>
> You have either a 6 channel PVT-6 or a 6\8 channel Basic Oncore. Both
> share size, power and I\O specifications. I'll send the Basic Oncore
> Engineering Notes to you off list.
>
> We'll  also  post the Engineering Notes to our website for others who
> might be interests in this early nineties legacy Motorola product By
> Tuesday: http://www.synergy-gps.com/index.php?option=com_content;
> task=view=42=89.
>
> Art Sepin
>
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of CIW308
> VE6OH
> Sent: Sunday, November 13, 2016 1:29 PM
> To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com>
> Subject: [time-nuts] GPS Model ?
>
> Any idea what unit this is?
> Has the markings:
> Motorola
>  7ST5H on a bar code
>  TM-AC on the PCB
>  BV-AC  M447D  on PCB
>  84D43215M03   on PCB
>
> Looks similar to the old ONCORE stuff.
> This unit has a BNC added to the Antenna.
>
> Did some searching but no luck yet.
>
> Hope the attachments go thru.
>
> Thanks in advance.
>
> Mitch
>
>
>
> J. T. (Mitch)  [Amateur radio  VE6OH]  [CFARS  CIW308] email
> mi...@andor.net
> Mobile Cellular 780 446 8958  SKYPE  USER ID   "MITCH-VE6OH"
>
> Past RAC Director for Alberta, NWT, NU  https://na01.safelinks.
> protection.outlook.com/?url=HTTP%3A%2F%2FWWW.RAC.CA=
> 01%7C01%7Cart%40synergy-gps.com%7C85efe09a17e0420e07ac08d40c10cd44%
> 7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C1=0Xaed5Ff0AHg42sDZd%
> 2BYbKdFEHAC%2FKYOmnIL%2Bc5mecY%3D=0
>
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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] GPS Model ?

[Art Sepin]

Mitch,

You have either a 6 channel PVT-6 or a 6\8 channel Basic Oncore. Both share 
size, power and I\O specifications. I'll send the Basic Oncore Engineering 
Notes to you off list. 

We'll  also  post the Engineering Notes to our website for others who might be 
interests in this early nineties legacy Motorola product By Tuesday: 
http://www.synergy-gps.com/index.php?option=com_content=view=42=89.

Art Sepin


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of CIW308 VE6OH
Sent: Sunday, November 13, 2016 1:29 PM
To: Discussion of precise time and frequency measurement 
Subject: [time-nuts] GPS Model ?

Any idea what unit this is?
Has the markings:
Motorola
 7ST5H on a bar code
 TM-AC on the PCB
 BV-AC  M447D  on PCB
 84D43215M03   on PCB

Looks similar to the old ONCORE stuff.
This unit has a BNC added to the Antenna.

Did some searching but no luck yet.

Hope the attachments go thru.

Thanks in advance.

Mitch



J. T. (Mitch)  [Amateur radio  VE6OH]  [CFARS  CIW308] email  mi...@andor.net
Mobile Cellular 780 446 8958  SKYPE  USER ID   "MITCH-VE6OH"

Past RAC Director for Alberta, NWT, NU  
https://na01.safelinks.protection.outlook.com/?url=HTTP%3A%2F%2FWWW.RAC.CA=01%7C01%7Cart%40synergy-gps.com%7C85efe09a17e0420e07ac08d40c10cd44%7Cc81f9fdec0e04d8c95779afaa0cad9ed%7C1=0Xaed5Ff0AHg42sDZd%2BYbKdFEHAC%2FKYOmnIL%2Bc5mecY%3D=0

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[time-nuts] Do the HP 5334A & 5335A counter/timers take the same oven oscillator?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Would it be possible to remove an OCXO from an 8334A 100 MHz counter/timer
and fit it in a 8335A 200 MHz counter/timer?

Would the TXCO from the 8335A then fit in the 8334A so that the 100 MHz
unit?

Are the OCXOs similar,  identical or incompatible?

I expect a detailed look at the service manuals would answer at least some
of the questions,  but I only have access to a mobile phone now, so are
hoping that someone might know.  In any case, different part numbers might
actually work,  even if not as stable as the correct OCXO.

Dave

Dr David Kirkby
Managing Director
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 07910 441670 / +44 7910 441670 (0900-2100 GMT)
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[time-nuts] DDS spurs (was: Secondary phase noise standard & FE405)

[Attila Kinali]

On Sun, 13 Nov 2016 11:03:31 -0500
Tim Shoppa  wrote:

> Some AD DDS app notes give examples of spurs and choosing nearby (but not
> exactly on freq) numbers that are much less bad for spurs - or at least
> that move the spurs outside the cleanup filters/loops. I don't know of a
> general example or even code that does this in a general way.
> 
> One paper I like on the subject is this:
> http://ttcla.org/vsreinhardt/DDS%20spur%20reduction%20techniques.pdf

A treatment of the topic that I found quite good is [1].
The spurs of DDS are very similar to those of delta-sigma modulators
(a DDS is delta-sigma modulator with a non-linear output mapping)
and as far as I have seen, there are more analysis on the spurs of
DS-modulators than on DDS systems (for a good reference on DS-modulators
see [2]). The DDS spur reduction systems all vere very similar to what
has been done to DS-modulators, like using a second or third order
DS-modulator instead of a simple phase accumulator and using more
bits in the sin/cos output and then using a first or second order
DS-modulator there.


Attila Kinali

[1] "Exact Analysis of DDS Spurs and SNR due to Phase Truncation and
Arbitrary Phase-to-Amplitude Errors", by Torosyan and Wilson, 2005
http://tycho.usno.navy.mil/ptti/ptti2005/paper8.pdf

[2] "Understanding Delta-Sigma Converters" by Schreier and Temes, 2005

-- 
Malek's Law:
Any simple idea will be worded in the most complicated way.
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Re: [time-nuts] Secondary phase noise standard & FE405

[Bob Camp]

Hi

The “sure fire” way to reduce the spurs is to go to a divisor that “fits” in to 
the DAC bit width. If you have a 12 bit dac, those points happen at Fclock / 
2^12.
For Time Nut sort of stuff that’s pretty coarse tuning. 

Bob

> On Nov 13, 2016, at 11:03 AM, Tim Shoppa  wrote:
> 
> Some AD DDS app notes give examples of spurs and choosing nearby (but not
> exactly on freq) numbers that are much less bad for spurs - or at least
> that move the spurs outside the cleanup filters/loops. I don't know of a
> general example or even code that does this in a general way.
> 
> One paper I like on the subject is this:
> http://ttcla.org/vsreinhardt/DDS%20spur%20reduction%20techniques.pdf
> 
> P.S. I just like saying "Wheatley Jitter Injector". Not for those who are
> embarrassed easily... Almost as good as "Wankel Rotary Engine".
> 
> One of
> 
> On Sat, Nov 12, 2016 at 8:13 PM, Hal Murray  wrote:
> 
>> 
>> kb...@n1k.org said:
>>> Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS
>>> spurs come  straight through. Since the FE-405 compensates for all sorts
>> of
>>> things, the DDS moves around a lot. Even a one bit change on a DDS will
>> move
>>> spurs around. With an ever changing  DDS, you have an ever changing
>> forest
>>> of “stuff” on the output.
>> 
>> Is there a web page or such telling me where the spurs will be on a DDS
>> for a
>> particular constant?
>> 
>> 
>> --
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
>> 
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Re: [time-nuts] Secondary phase noise standard & FE405

[Tim Shoppa]

Some AD DDS app notes give examples of spurs and choosing nearby (but not
exactly on freq) numbers that are much less bad for spurs - or at least
that move the spurs outside the cleanup filters/loops. I don't know of a
general example or even code that does this in a general way.

One paper I like on the subject is this:
http://ttcla.org/vsreinhardt/DDS%20spur%20reduction%20techniques.pdf

P.S. I just like saying "Wheatley Jitter Injector". Not for those who are
embarrassed easily... Almost as good as "Wankel Rotary Engine".

One of

On Sat, Nov 12, 2016 at 8:13 PM, Hal Murray  wrote:

>
> kb...@n1k.org said:
> > Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS
> > spurs come  straight through. Since the FE-405 compensates for all sorts
> of
> > things, the DDS moves around a lot. Even a one bit change on a DDS will
> move
> > spurs around. With an ever changing  DDS, you have an ever changing
> forest
> > of “stuff” on the output.
>
> Is there a web page or such telling me where the spurs will be on a DDS
> for a
> particular constant?
>
>
> --
> These are my opinions.  I hate spam.
>
>
>
>
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Re: [time-nuts] quartz drift rates, linear or log

[Bob Camp]

Hi



> On Nov 13, 2016, at 9:34 AM, Artek Manuals  wrote:
> 
> Tom et all
> 
> While our instinct based on some "pre- knowledge" of the aging and drift 
> processes is to try and fit these to linear or logarithmic curves there is a 
> third possibility . That is, in fact the aging is not exactly either and may 
> be better represented in fact be some kind of polynomial curve. The fact that 
> there may be  more than one drift and aging process at play here would also 
> fit this hypothesis. Ii makes my head hurt to think about how one would 
> derive the polynomial. Following this thread further ( and not to discourage 
> your endeavor) but the entire history of each Xtal may be more of a factor 
> than we initially surmised as well. Each xtal is at a different point in its 
> journey through TIME and its history may have as much or more to do with how 
> it behaves at this point in TIME than we can characterize

Having fit a few (quite a few) OCXO’s and TCXO's to various curves … the log 
curve in 55310 is about as good as any you can use. Polynomial curves will (in 
general) give you a real mess … The most common outcome is that your time 
interval is to short / your data to noisy / your aging to low to get a real fit 
with a good confidence estimate. The statement “as good as” should be taken in 
that context.  The only real way to validate the fit is to go ahead and run the 
parts for another month or year to see what happens over various time periods. 
Because of the inevitable noise in the data, the curve fit is a bit tricky….

Bob

> 
> Statistically it is also advisable  to throw out (from the curve fitting 
> exercise anyway) unusual units that are clearly not like all the other kids 
> since they are clearly marching to a different drummer and for the purpose of 
> this exercise are adding to the NOISE of the analysis 8^)
> 
> Dave
> 
> 
> 
> -- 
> Dave
> manu...@artekmanuals.com
> www.ArtekManuals.com
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Re: [time-nuts] 5071A with ATTENTION flashing

[Li Ang]

Hi Tom
It looks very clean inside. I think they should be from some lab. There is 
one with a label CEVA xx on it. 
I told him all the information I collected from the serial port. As a 
reward to travel 200km help him determine the status of these 5071s, he gave me 
2 PRS10 rubidium oscillators. 
I also told him to keep the leaky one running for days and see what's going 
on. If it goes to normal, price will x2 or more. 


regards
Li Ang


---Original---
From: "Tom Van Baak"
Date: 2016/11/13 19:34:59
To: "Discussion of precise time and frequency measurement";
Subject: Re: [time-nuts] 5071A with ATTENTION flashing


> Since the ion pump current was dropping slowly.(80uA to 76uA in 1 hour), is 
> it possible to be back to normal?

Hi Li,

Yes, is it possible. Never give up on ion current. Give it hours, give it days 
if necessary.

Monitor the LCD or syst:print? periodically and plot the trend. The trend may 
be linear (you may only need to wait for hours). The trend my be logarithmic 
(you may need to wait for days). If the trend looks like it will eventually 
drop below 1 uA that is good news. You just have to wait. If the 5071A gives a 
fatal error and turns off the ion pump for safety, then power cycle to try 
again.

What you are seeing is not normal behavior. But given the chance that you might 
get a tube that works, even for a little while, that is worth something. Do you 
know where these 5071A were installed, or what they were used for?

If it looks like the ion pump current will never drop to 1 uA, even after 
several days, then you may have a vacuum leak or failed ion pump or too much 
outgassing or something. Try swapping tubes to see if the new frame shows a 
similar ion pump reading and trend. If so, then both frames are ok and the tube 
is bad. I don't know of a fix for this. Cesium tubes fail for many reasons, not 
just running out of cesium.

/tvb

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Re: [time-nuts] quartz drift rates, linear or log

[Tom Van Baak]

>> http://leapsecond.com/pages/tbolt/TBolt-10day-fit1-e10.gif

> Hi Tom,
>
> Fascinating when you've done that linear fit - many of the plots now look 
> very similar,
> suggesting environmental conditions?  From that it would now be nice to log 
> temperature,
> pressure, humidity, (& mains voltage?), and see if there is any correlation 
> there.
>
> Wonderful to see plots of such a large group - well done!
>
> Peter

That's correct. Yes, I am also logging environmental parameters. Stay tuned for 
that. Also, you may have noticed the "thermal events" that I deliberately 
caused in the lab once in a while to make environmental correlations more 
obvious.

The end goal is not only to extract the approximate tempco of each unit through 
correlation but also to post-process the data to partially back out the 
temperature component and produce a set of second residual plots. So you go 
from raw data, to measuring drift, to removing drift, to measuring tempco, to 
removing tempco. At this point you get closer to revealing the intrinsic 
performance of the oscillator.

I did the same for "Clock B" last year:

http://leapsecond.com/pend/clockb/2015-tvb-Greenwich-ClockB-ppt.pdf
http://leapsecond.com/pend/clockb/

In fact you don't really need to go through the plotting and fitting steps. 
There are standard techniques to fit N-dimensional models to data. So a 
frequency and temperature time series goes in -- and best fit linear drift and 
temperature coefficient estimates comes out. This will be automated, but for 
now I like the plots because they are more educational. Also the eye is 
extremely good at spotting interesting or unforeseen things that math and 
statistics are blind to.

/tvb

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Re: [time-nuts] quartz drift rates, linear or log

[Peter Vince]

Hi Tom,

 Fascinating when you've done that linear fit - many of the plots now
look very similar, suggesting environmental conditions?  From that it would
now be nice to log temperature, pressure, humidity, (& mains voltage?), and
see if there is any correlation there.

 Wonderful to see plots of such a large group - well done!

  Peter


On 13 November 2016 at 13:05, Tom Van Baak  wrote:

> ...
> But, when you apply a 10-day linear fit to each DUT, you get a new plot.
> Attached. Also at:
>
> http://leapsecond.com/pages/tbolt/TBolt-10day-fit1-e10.gif
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Re: [time-nuts] quartz drift rates, linear or log

[Artek Manuals]

Tom et all

While our instinct based on some "pre- knowledge" of the aging and drift 
processes is to try and fit these to linear or logarithmic curves there 
is a third possibility . That is, in fact the aging is not exactly 
either and may be better represented in fact be some kind of polynomial 
curve. The fact that there may be  more than one drift and aging process 
at play here would also fit this hypothesis. Ii makes my head hurt to 
think about how one would derive the polynomial. Following this thread 
further ( and not to discourage your endeavor) but the entire history of 
each Xtal may be more of a factor than we initially surmised as well. 
Each xtal is at a different point in its journey through TIME and its 
history may have as much or more to do with how it behaves at this point 
in TIME than we can characterize


Statistically it is also advisable  to throw out (from the curve fitting 
exercise anyway) unusual units that are clearly not like all the other 
kids since they are clearly marching to a different drummer and for the 
purpose of this exercise are adding to the NOISE of the analysis 8^)


Dave



--
Dave
manu...@artekmanuals.com
www.ArtekManuals.com
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Re: [time-nuts] Secondary phase noise standard & FE405

[Bob Camp]

Hi


> On Nov 13, 2016, at 2:55 AM, Gerhard Hoffmann  wrote:
> 
> Am 12.11.2016 um 23:52 schrieb Bob Camp:
>> Hi
>> 
>> Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS 
>> spurs come
>> straight through. Since the FE-405 compensates for all sorts of things, the 
>> DDS moves
>> around a lot. Even a one bit change on a DDS will move spurs around. With an 
>> ever changing
>> DDS, you have an ever changing forest of “stuff” on the output.
> I would not expect a lot of dynamics after a month of cont. power up. And the 
> spurs
> do not move and they don't average away, at least not within my limits of 
> boredom.
> 
> The PLL bandwidth seems to be 50 Hz, so the forest from 100KHz to 5MHz is
> far out. That seems somewhat weird and raised doubt together
> with the power level being out of spec.

The spurs you need to watch are under 50Hz. They are the ones from the DDS. The 
higher
stuff is from the microprocessor. 

Bob

> 
>> Not the best thing for a “standard” …..
> I've tried to kill 2 birds with one stone. The FE405 had collected dust for
> months and still was mostly untested.
> 
> The oscillator is not part of the "standard"; I could have used a BVA or
> a maser by just plugging in. I just needed a centre frequency with a
> few dBm for the E5052B to lock on.
> 
> All I want is some known phase noise reference reference lines
> for my private phase detector experiments. Recalibating the
> phase detector by modulating oscillators on different frequencies
> is no fun if you change the Schottkies every 2 minutes.
> 
> regards, Gerhard
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Re: [time-nuts] quartz drift rates, linear or log

[Tom Van Baak]

Thanks for all the comments on this thread. Here is the first set of replies:



Don Latham:
> Interesting, Tom. I don't think I see any of those pesky grain boundary 
> shifts or readjustments in the lattice structure? If I remember, these 
> can cause instant shifts in frequency that do not heal?
> Don

In this experiment I was more interested in long-term frequency. I think the 
frequency jumps you speak of may be at a finer level than I was measuring. They 
are easier to see if you use a TimePod and continuously collect data every 
second. They are harder to spot if you use a frequency counter and collect data 
once an hour.

That said, you can see that CH03 exhibits more spikes than any of the others 
and it will be set aside for a closer look. The nice thing about this stage of 
my time nut hobby is that I am no longer looking for the best oscillator. Now 
oscillators that are weird are interesting to me.



Attila:
> These look like textbook examples of random walk frequency modulation.
> As this is a random process it is not surprising that they look different
> for each oscillator. 

Yes and no. Look again at:

http://leapsecond.com/pages/tbolt/TBolt-10day-fit0-e10.gif

Many of the plots differ in appearance and it's clearly not always random walk. 
Each oscillator's drift rate, short-term noise (hours) and long-term noise 
(days) contributes to the appearance of the plot.

But, when you apply a 10-day linear fit to each DUT, you get a new plot. 
Attached. Also at:

http://leapsecond.com/pages/tbolt/TBolt-10day-fit1-e10.gif

And then, yes, the dominant noise is very much random walk FM. Still, there is 
a variety in performance: some more noisy than others. This shows up nicely in 
the HDEV plots or drift removed ADEV plots. Those are important because when an 
OCXO is used in a GPSDO, the linear-fitted residual data is much more relevant 
than the raw data.

To put it another way, the first plot above makes you think some of these OCXO 
will make a far better GPSDO than others. But the second plot shows they may 
all be quite similar. The 2nd order term of the loop enables this.



Attila Kinali:
> Do you know what caused the frequency jump of CH18?

Good eye. I think that was me doing EFC testing. I can check my notes. It's not 
the TBolt or OCXO.



Bob Stewart:
> So, are you measuring OCXO stability or EFC stability?
> Bob

I measured the 10 MHz coming out of the BNC connector. The TBolt's are 
free-running (no GPS, no disciplining) and DAC/EFC is forced to 0 volts to 
reduce any impact it may have.

I have also done EFC testing on each unit; that's a separate report for later. 
In this thread I mostly just wanted to show examples of log and linear drift 
and to convey that long-term (days, weeks) logarithmic trends are effectively 
linear trends over shorter-term (hours, days).



Tom Miller:
> Just out of curiosity, what is the age of each of these Tbolts? (i.e. date 
> codes?)

These TBolt's are all from the original 2008 TAPR group buy. The Trimble date 
codes range from 2002 to 2005. These are US-units, not Chinese eBay imports.



Charles Steinmetz:
> When the purpose is correcting a GPSDO local oscillator during holdover, 
> it depends on how long one expects to trust the corrected frequency. 
> Practical realities make it pointless to trust corrections longer than a 
> day or so, if that long.  At that scale, these all look pretty linear.

I agree. See especially the new linear-drift-removed plot I posted for Attila 
above (and attached).



Jim Lux:
> I think this is a general rule: when they make precision oscillators 
> (USOs) for spacecraft, they make a fairly large batch (a couple dozen) 
> to some intermediate level of assembly, and then they run them for a 
> while and watch them, and from that, they pick the "good" ones.  (where 
> good is somewhat mission dependent).

Right. Many of us time nuts have done the same with 10811A oscillators. You 
just keep buying them here and there over the years, comparing them, and keep 
the unusually good one that's down in the low -13's.



/tvb
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Re: [time-nuts] 5071A with ATTENTION flashing

[Tom Van Baak]

> Since the ion pump current was dropping slowly.(80uA to 76uA in 1 hour), is 
> it possible to be back to normal?

Hi Li,

Yes, is it possible. Never give up on ion current. Give it hours, give it days 
if necessary.

Monitor the LCD or syst:print? periodically and plot the trend. The trend may 
be linear (you may only need to wait for hours). The trend my be logarithmic 
(you may need to wait for days). If the trend looks like it will eventually 
drop below 1 uA that is good news. You just have to wait. If the 5071A gives a 
fatal error and turns off the ion pump for safety, then power cycle to try 
again.

What you are seeing is not normal behavior. But given the chance that you might 
get a tube that works, even for a little while, that is worth something. Do you 
know where these 5071A were installed, or what they were used for?

If it looks like the ion pump current will never drop to 1 uA, even after 
several days, then you may have a vacuum leak or failed ion pump or too much 
outgassing or something. Try swapping tubes to see if the new frame shows a 
similar ion pump reading and trend. If so, then both frames are ok and the tube 
is bad. I don't know of a fix for this. Cesium tubes fail for many reasons, not 
just running out of cesium.

/tvb

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Re: [time-nuts] Swagelok and metric tubing question

[Poul-Henning Kamp]

In message , Gary Woods writes:
>On Sat, 12 Nov 2016 13:05:56 -0800, you wrote:
>
>>Does it leak through cracks or migrate through metal?
>
>I was kinda wondering about that.  Isn't H the escape artist of the
>periodic table?

Indeed.

In particular it seeps through almost all metals.

(See also: https://en.wikipedia.org/wiki/Hydrogen_embrittlement)

The canonical filter method for hydrogen is to press it through a
"filter" which is a of solid slab of Palladium.

Helium is almost as bad, but is better in leak-checks because it
is non-reactive.

-- 
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] Secondary phase noise standard & FE405

[Gerhard Hoffmann]

Am 12.11.2016 um 23:52 schrieb Bob Camp:

Hi

Yes, the FE-405 uses a DDS and a cleanup. Inside the cleanup loop the DDS spurs 
come
straight through. Since the FE-405 compensates for all sorts of things, the DDS 
moves
around a lot. Even a one bit change on a DDS will move spurs around. With an 
ever changing
DDS, you have an ever changing forest of “stuff” on the output.
I would not expect a lot of dynamics after a month of cont. power up. 
And the spurs
do not move and they don't average away, at least not within my limits 
of boredom.


The PLL bandwidth seems to be 50 Hz, so the forest from 100KHz to 5MHz is
far out. That seems somewhat weird and raised doubt together
with the power level being out of spec.


Not the best thing for a “standard” …..

I've tried to kill 2 birds with one stone. The FE405 had collected dust for
months and still was mostly untested.

The oscillator is not part of the "standard"; I could have used a BVA or
a maser by just plugging in. I just needed a centre frequency with a
few dBm for the E5052B to lock on.

All I want is some known phase noise reference reference lines
for my private phase detector experiments. Recalibating the
phase detector by modulating oscillators on different frequencies
is no fun if you change the Schottkies every 2 minutes.

regards, Gerhard
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Re: [time-nuts] 5071A with ATTENTION flashing

[Li Ang]

HI
  I just came back from another 5071a seller. 
#1-#3 fatal error: max emult. 
#4 fatal error: overcureent (about 80uA) 
I put the tube from #1 to #4. #4 became a "max emult" one. 

I think the tube #1 is really dead and the circuit of #4 is functional.

Since the ion pump current was dropping slowly.(80uA to 76uA in 1 hour), is it 
possible to be back to normal?

regards
LiAng 
BI7LNQ
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