Re: [time-nuts] Replacement A9 boards for the HP 5065A

[Bill Hawkins]

Group,

After 40 years of doing PID control for industrial processes, I'm used
to an error tolerance of 10E-3. So I couldn't understand an integrator
with a 10 K resistor and a 5 mfd capacitor.

But this is time nuts, and the tolerance is more like 10E-13.

An integrator as a controller takes any deviation from zero error
voltage and moves the output in a direction that will return the error
to zero.

In this case, 10 K is the practical lower limit to the input resistor
for the desired time constant, with 5 mfd as a practical upper limit.
Any current flowing in that resistor changes the value of zero error,
which causes the output to move when the actual error is zero. This
makes the frequency wander. The current can come from the opamp bias or
capacitor leakage when the output is not zero.

Similarly, a change in the opamp zero offset causes a false error which
makes the output move when it shouldn't.

So I withdraw my comment about aluminum electrolytics, which was made
without a timenuts perspective.

Determining maximum error currents and offsets is simply a matter of
mathematics, which is left as an exercise for the student.

Regards,
Bill Hawkins

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Re: [time-nuts] FRK

[Tom Van Baak]

Bert's M100 Rb teardown photos are now here:

http://leapsecond.com/bert/m100.htm

/tvb

- Original Message - 
From: "ewkehren via time-nuts" 
To: "Discussion of precise time and frequency measurement" 
Sent: Sunday, February 25, 2018 6:05 AM
Subject: [time-nuts] FRK


We have pictures of the guts of a M100 the file is 1.8 M off list or permission 
to post

Bert Kehren 

Sent from my Galaxy Tab® A
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[time-nuts] Assorted replies, and request for info

[John Miles]

Request for data from an off-list friend who is looking for info on an Ovenaire 
OCXO and/or the instrument it was used in:

> Could you send a post on my behalf asking if anyone else has an 
> Ovenaire 42-15 or if not, a Spectracom 8131 Frequency Standard Oscillator. 

This is from Dennis Tillman, who can be reached directly at dennis (at) 
ridesoft.com.

> Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What
> do you think that is? On a hunch I opened the front panel and reset the
> blinking amber battery alarm lamp, and voila, that noise went away. Makes
> sense when you think of the power variations associated with a blinking
> incandescent lamp.

I hadn't heard of that one, but some other examples include 1-pps crosstalk on 
the 10 MHz output of some of the HP GPSDOs (which I've run into myself), and 
the inadvertent ~5 MHz comb generator that drives the indicator LED on the HP 
5370's reference clock interface PCB that Bruce Griffiths noticed several years 
ago.  Presumably neither of these faux pas were bad enough to be noticed by the 
original designers or their paying customers, but they probably would have been 
fixed if they had come to the attention of the people involved.  Goes to show 
how improved instrumentation can be a curse as well as a blessing.

Poul-Henning's observation on the 5065A integrator cap highlights the risk of 
erring too far in the opposite direction:

> When I experimented, I could hardly find *any* property that mattered
> for that capacitor, not even the exact capacitance, because the
> adjustment procedue handles that.

I have a feeling this is true of most of the components in that circuit.  The 
nice thing about an integrator is that it's also a low-pass filter.  And the 
nice thing about a closed loop is that it's, well, closed.

Before spending too much time arguing about whether the opamp should be 
replaced with an LT1012 or an AD797 or a cryocooled tunnel diode or whatever, 
I'd suggest replacing it with a 741 and seeing how much *worse* the performance 
gets.  It is easier to measure the effect of that kind of change.  If there is 
little or no harm in using the crappiest opamp you can find, that means that 
you can safely stop worrying about what the best one might be.  

> One of the TimePods that I had access to in the past was particularly good
> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a
> lot which instrument the power transformer was in. For some weird 
> reason it was a good magnetometer at line frequencies. I never bothered to 
> send it back for analysis. Simply moving it onto the bench top (rather than 
> stacked on top of this or that) would take care of the issue.
> 
> As far as I could tell, it was just the one unit that had the issue. None of 
> the
> others in the fleet of TimePods seemed to behave this way. Given that they
> normally are very good at rejecting all sorts of crud and ground loops, it was
> somewhat odd to see.

I've seen similar behavior here, not only with respect to units responding 
differently to 60/120 Hz magnetic interference, but also at higher offsets in 
the absence of an obvious coupling mechanism.  There was one case where a 
TimePod I was working with picked up an unstable low-level spur near 25 kHz 
from an LED aquarium light fixture several meters away.  Other units swapped 
into the same position did not show the spur at all, and I was never able to 
narrow down the cause with any certainty.  I don't have a good explanation for 
any of the above, unfortunately.

That being said, Phil Hobbs posted something on sci.electronics.design the 
other day that I thought was subtly insightful, even though he was just stating 
an obvious point.  Namely, ground loops are inherently very low impedance 
phenomena, often occurring in the milliohm range.  Especially when dealing with 
anodized aluminum hardware like the TimePod's enclosure, the difference between 
a test setup where all the coax shields act as a near-perfect shorted 
transformer turn versus one with significant loss might come down to small 
differences in fastener torque, or perhaps a missing star washer.  So it's 
possible to envision a scenario where tightening up all the proverbial loose 
screws actually makes a magnetically-coupled spur worse.  

Lifting a coax shield is usually not the best solution to ground loops, but 
Phil's offhand comment made me wonder about the effects of deliberately adding 
just a few ohms of series R.  It's on my list of things to look into when I 
have time.

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Allan variance by sine-wave fitting

[Magnus Danielson]

Hi,

On 02/26/2018 08:42 PM, Gerhard Hoffmann wrote:
> Am 26.02.2018 um 20:20 schrieb Tom Van Baak:
>> Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise
>> plot. What do you think that is? On a hunch I opened the front panel
>> and reset the blinking amber battery alarm lamp, and voila, that noise
>> went away. Makes sense when you think of the power variations
>> associated with a blinking incandescent lamp.
> 
> There was a Tektronix sampler that had a few ps sampling jitter to the tune
> of a blinking LED on the mainframe  :-)

I was just about to comment on that. The Tek 11803 / CSA803C TDR module
has a blinking LED with "HOT" TDR pulse. It however skews the timing so
a later firmware disabled the blinking.

Sadly to say, I don't have that FW on mine CSAs

Cheers,
Magnus
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Re: [time-nuts] Replacement A9 boards for the HP 5065A

[Poul-Henning Kamp]

In message 
, Wayne 
Holder writes:
>>> The only thing I could provok, was that almost all capacitors I
>>> tried were sensitive to touch.
>
>Most ceramic caps are sensitive to "micro phonics" via the piezoelectric
>effect, which can translate mechanical stress into electrical noise.

Yes, and unlike plastics, their mechanical resonance is sharp and
at frequencies where microphonics matter a lot.

Even then, a 4.7uF SMD multilayer ceramic mounted with two "looped"
wires for stress-relief worked just fine.

-- 
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] Replacement A9 boards for the HP 5065A

[Wayne Holder]

>> The only thing I could provok, was that almost all capacitors I
>> tried were sensitive to touch.

Most ceramic caps are sensitive to "micro phonics" via the piezoelectric
effect, which can translate mechanical stress into electrical noise.


https://e2e.ti.com/blogs_/archives/b/precisionhub/archive/2014/12/19/stress-induced-outbursts-microphonics-in-ceramic-capacitors-part-1

Wayne


On Mon, Feb 26, 2018 at 2:05 PM, Poul-Henning Kamp 
wrote:

> 
> In message 

Re: [time-nuts] Replacement A9 boards for the HP 5065A

[Poul-Henning Kamp]

In message 

Re: [time-nuts] Replacement A9 boards for the HP 5065A

[paul swed]

Well all this capacitor talk has me actually looking for the 5 uf cap.
When I picked up the 5065a it didn't work. This was in the late 90s and no
manual was available at that time.
I reverse engineered the system and guess what cap was bad? The integrator.
So not being all that smart, I hooked 2 X 10 UF caps in series. Been
working like a champ for 18 years.
Not obvious of what the downside of this approach was at all.
But I went out to mouser and have to say the selection of large capacitors
really is thin for PPS and PS. I did see the one picture of a yellow cap I
think from Germany.
The question really is what is the source and part number for a good cap.
does appear that the wima caps are carried by Mouser but may have long lead
times.
Regards
Paul
WB8TSL

On Sun, Feb 25, 2018 at 2:50 PM, Gerhard Hoffmann  wrote:

>
>
> Am 25.02.2018 um 13:46 schrieb Azelio Boriani:
>
>> The part number BFC234421475, on 
>> seems to be a Philips product, 2500 available, for 49.28 UAH
>> (Ukrainian Hryvnia, that is 1.77 USD). A mysterious capacitor...
>>
> Why not go to Mouser or DK, as usual?
>
> Or to the source itself:
> <  https://www.wima.de/en/  >
>
> (Abt. an hour of driving from where I'm now).
>
> BTW last time I bought some at DK/Mouser, there was
> a pricing artefact, in that 5% was cheaper than 10%
>
> :-)  Gerhard
>
>
>
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Re: [time-nuts] Allan variance by sine-wave fitting

[Chris Caudle]

On Mon, February 26, 2018 2:29 pm, Tom Van Baak wrote:
> BTW, a trick for blinking LED's -- use two of them out of phase: one that
> the user sees on the front panel and one that is blacked out or hidden
> inside. A flip-flop (Q and /Q) or even a set of inverters is all you need.
> The current draw thus remains constant in spite of the blinking.

You could also use a long-tail diff-pair, with the LED in the collector
circuit of just one side of the pair.  Only costs one extra transistor and
a few resistors and then the current draw is (close to) constant whether
the LED is on or off.

-- 
Chris Caudle


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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

> Yet another reason to nuke the battery and the A2 board. 

Yes. Then again, the effect is very minor when you look at the PN and ADEV 
plots. It falls into the category of "look how sensitive a TimePod is" more 
than "look how bad a 5065A is". And remember it's just a warning lamp, with a 
toggle switch to reset the blink.

> a PIC-DIV pull compared to the 1 pps section of one of these old beasts (Cs 
> or Rb)? 

Right, a PIC divider is much lower power, but if you're driving a 50R load 
that's still a lot of current. I suspect this is one reason why high-end 
standards use 10 or 20 us wide pulses and not 50% duty cycle square waves for 
their 1PPS outputs. Same power but 10 us is 50,000x less energy than 0.5 s. 
I've stopped using squares waves for 1PPS around here.

BTW, a trick for blinking LED's -- use two of them out of phase: one that the 
user sees on the front panel and one that is blacked out or hidden inside. A 
flip-flop (Q and /Q) or even a set of inverters is all you need. The current 
draw thus remains constant in spite of the blinking.

/tvb

- Original Message - 
From: "Bob kb8tq" 
To: "Discussion of precise time and frequency measurement" 
Sent: Monday, February 26, 2018 11:51 AM
Subject: Re: [time-nuts] Allan variance by sine-wave fitting


Hi

Yet another reason to nuke the battery and the A2 board. 

It is amazing just how small a signal can mess things up at the levels involved 
in
a good frequency standard. The old “when in doubt, throw it out” mantra may be
a good one to keep in mind relative to a lot of add on features…. how much does
a PIC-DIV pull compared to the 1 pps section of one of these old beasts (Cs or 
Rb)? 

Lots to think about. 

Bob

> On Feb 26, 2018, at 2:20 PM, Tom Van Baak  wrote:
> 
>> at telling you it was sitting on top of a power transformer. It didn’t 
>> matter a lot
> 
> I did ten runs of various standards that were within a couple of meters of 
> the bench; the TimePod did not move the entire time. Each standard had a 
> different looking PN plot, so I'm pretty sure the 120 Hz spur we see is the 
> 5065A itself, not something in the lab.
> 
> File http://leapsecond.com/tmp/2018b-Ralph-2-pn.png is attached.
> 
> Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What 
> do you think that is? On a hunch I opened the front panel and reset the 
> blinking amber battery alarm lamp, and voila, that noise went away. Makes 
> sense when you think of the power variations associated with a blinking 
> incandescent lamp.
> 
> /tvb
> 
> - Original Message - 
> From: "Bob kb8tq" 
> To: "Tom Van Baak" ; "Discussion of precise time and 
> frequency measurement" 
> Sent: Monday, February 26, 2018 7:00 AM
> Subject: Re: [time-nuts] Allan variance by sine-wave fitting
> 
> 
> Hi
> 
> One of the TimePods that I had access to in the past was particularly good
> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a lot
> which instrument the power transformer was in. For some weird reason it
> was a good magnetometer at line frequencies. I never bothered to send it
> back for analysis. Simply moving it onto the bench top (rather than stacked 
> on top of this or that) would take care of the issue.
> 
> As far as I could tell, it was just the one unit that had the issue. None of 
> the
> others in the fleet of TimePods seemed to behave this way. Given that they
> normally are very good at rejecting all sorts of crud and ground loops, it 
> was 
> somewhat odd to see. 
> 
> Bob
> 
>> On Feb 26, 2018, at 7:13 AM, Tom Van Baak  wrote:
>> 
>>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
>> 
>> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
>> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
>> to run at that resolution so effects like this show up. Once that's done, 1 
>> ms resolution is overkill.
>> 
>> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
>> and TDEV plots.
>> 
>> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
>> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
>> It's best seen as a bump at ~4 ms in the TDEV plot.
>> 
>> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 
>> Hz.
>> 
>> /tvb
>> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>
> 
> <2018b-Ralph-2-pn.png>___
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Re: [time-nuts] Allan variance by sine-wave fitting

[Bob kb8tq]

Hi

Yet another reason to nuke the battery and the A2 board. 

It is amazing just how small a signal can mess things up at the levels involved 
in
a good frequency standard. The old “when in doubt, throw it out” mantra may be
a good one to keep in mind relative to a lot of add on features…. how much does
a PIC-DIV pull compared to the 1 pps section of one of these old beasts (Cs or 
Rb)? 

Lots to think about. 

Bob

> On Feb 26, 2018, at 2:20 PM, Tom Van Baak  wrote:
> 
>> at telling you it was sitting on top of a power transformer. It didn’t 
>> matter a lot
> 
> I did ten runs of various standards that were within a couple of meters of 
> the bench; the TimePod did not move the entire time. Each standard had a 
> different looking PN plot, so I'm pretty sure the 120 Hz spur we see is the 
> 5065A itself, not something in the lab.
> 
> File http://leapsecond.com/tmp/2018b-Ralph-2-pn.png is attached.
> 
> Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What 
> do you think that is? On a hunch I opened the front panel and reset the 
> blinking amber battery alarm lamp, and voila, that noise went away. Makes 
> sense when you think of the power variations associated with a blinking 
> incandescent lamp.
> 
> /tvb
> 
> - Original Message - 
> From: "Bob kb8tq" 
> To: "Tom Van Baak" ; "Discussion of precise time and 
> frequency measurement" 
> Sent: Monday, February 26, 2018 7:00 AM
> Subject: Re: [time-nuts] Allan variance by sine-wave fitting
> 
> 
> Hi
> 
> One of the TimePods that I had access to in the past was particularly good
> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a lot
> which instrument the power transformer was in. For some weird reason it
> was a good magnetometer at line frequencies. I never bothered to send it
> back for analysis. Simply moving it onto the bench top (rather than stacked 
> on top of this or that) would take care of the issue.
> 
> As far as I could tell, it was just the one unit that had the issue. None of 
> the
> others in the fleet of TimePods seemed to behave this way. Given that they
> normally are very good at rejecting all sorts of crud and ground loops, it 
> was 
> somewhat odd to see. 
> 
> Bob
> 
>> On Feb 26, 2018, at 7:13 AM, Tom Van Baak  wrote:
>> 
>>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
>> 
>> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
>> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
>> to run at that resolution so effects like this show up. Once that's done, 1 
>> ms resolution is overkill.
>> 
>> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
>> and TDEV plots.
>> 
>> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
>> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
>> It's best seen as a bump at ~4 ms in the TDEV plot.
>> 
>> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 
>> Hz.
>> 
>> /tvb
>> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>
> 
> <2018b-Ralph-2-pn.png>___
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Re: [time-nuts] Allan variance by sine-wave fitting

[Gerhard Hoffmann]

Am 26.02.2018 um 20:20 schrieb Tom Van Baak:

Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What do 
you think that is? On a hunch I opened the front panel and reset the blinking 
amber battery alarm lamp, and voila, that noise went away. Makes sense when you 
think of the power variations associated with a blinking incandescent lamp.


There was a Tektronix sampler that had a few ps sampling jitter to the tune
of a blinking LED on the mainframe  :-)

Cheers, Gerhard
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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

> at telling you it was sitting on top of a power transformer. It didn’t matter 
> a lot

I did ten runs of various standards that were within a couple of meters of the 
bench; the TimePod did not move the entire time. Each standard had a different 
looking PN plot, so I'm pretty sure the 120 Hz spur we see is the 5065A itself, 
not something in the lab.

File http://leapsecond.com/tmp/2018b-Ralph-2-pn.png is attached.

Fun fact -- there's a wide spur at ~2 Hz on the 5065A phase noise plot. What do 
you think that is? On a hunch I opened the front panel and reset the blinking 
amber battery alarm lamp, and voila, that noise went away. Makes sense when you 
think of the power variations associated with a blinking incandescent lamp.

/tvb

- Original Message - 
From: "Bob kb8tq" 
To: "Tom Van Baak" ; "Discussion of precise time and 
frequency measurement" 
Sent: Monday, February 26, 2018 7:00 AM
Subject: Re: [time-nuts] Allan variance by sine-wave fitting


Hi

One of the TimePods that I had access to in the past was particularly good
at telling you it was sitting on top of a power transformer. It didn’t matter a 
lot
which instrument the power transformer was in. For some weird reason it
was a good magnetometer at line frequencies. I never bothered to send it
back for analysis. Simply moving it onto the bench top (rather than stacked 
on top of this or that) would take care of the issue.

As far as I could tell, it was just the one unit that had the issue. None of the
others in the fleet of TimePods seemed to behave this way. Given that they
normally are very good at rejecting all sorts of crud and ground loops, it was 
somewhat odd to see. 

Bob

> On Feb 26, 2018, at 7:13 AM, Tom Van Baak  wrote:
> 
>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
> 
> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
> to run at that resolution so effects like this show up. Once that's done, 1 
> ms resolution is overkill.
> 
> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
> and TDEV plots.
> 
> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
> It's best seen as a bump at ~4 ms in the TDEV plot.
> 
> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 Hz.
> 
> /tvb
> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>

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[time-nuts] Replacement Backup Battery for 5065A?

[Ed Palmer]

On 2018-02-26 11:00 AM, Corby wrote:

Also I usually remove a battery A2 and install two shottky diodes on the
underside of A2s chassis jack.

Non-battery units have an A2 that just has these two diodes on it.


On mine, I didn't bother with schottky diodes, I just used half of a 
bridge rectifier that I bolted to the chassis.  Removing the battery 
charger version of the A2 board also removed a significant amount of 
heat from the unit.  That board runs quite warm!


Another interesting point about removing the A2 board is that in 
addition to freeing up a card slot, it frees up the transformer winding 
that was used for the battery charger.  Maybe use that to build a 5V 
supply for some new add-on.  The A2 board was rated for ~25V @150 ma or 
~3.75W.  At 5V, that's 0.75A.  You'd probably have to use a switching 
supply.  Extra care would be required to make sure that the supply's 
switching noise didn't degrade the unit's performance.


Ed

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[time-nuts] Replacement Backup Battery for 5065A?

[cdelect]

I agree with Bert,

I always remove the battery.

They will cause grief eventually!

Use either in UPS or the separate DC input jack on the rear.

One note, if the battery is removed and the battery charge switch is in
the position to light the front panel lamp you will degrade the stability
of the unit! Removing the bulb clears it up! Never bothered to figure out
why!

Also I usually remove a battery A2 and install two shottky diodes on the
underside of A2s chassis jack.

Non-battery units have an A2 that just has these two diodes on it.

Cheers,

Corby

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Re: [time-nuts] Replacement A9 boards for the HP 5065A

[ewkehren via time-nuts]

We have decided to go with the 1012 do we need to do any thing with pin 5Bert 
kehren


Sent from my Galaxy Tab® A
 Original message From: Attila Kinali  Date: 
2/26/18  9:53 AM  (GMT-05:00) To: Discussion of precise time and frequency 
measurement  Subject: Re: [time-nuts] Replacement A9 boards 
for the HP 5065A 
On Sat, 24 Feb 2018 23:44:16 -0500
Charles Steinmetz  wrote:

> Given the relatively low resistances at the op-amp inputs (10k ohms), 
> the ultra-low input "bias" (leakage) current of the 6240 is simply 
> unnecessary.  Any offset due to the input currents (within the general 
> range of any of these op-amps) is insignificant compared to the op-amp's 
> offset voltage.  Thus, offset voltage, offset voltage tempco, and offset 
> voltage long-tem drift are the critical parameters (as Poul-Henning 
> pointed out).  And here, the 1012 is clearly the best of the three.  In 
> addition to having the lowest input offset spec, the 1012 has guaranteed 
> maximum specifications for these important parameters.  The 6240 (for 
> good reason) is *not even rated* for long-term stability (drift). 
> (Long-term offset stability is a particular weakness of CMOS op-amps.)

Oh.. right, I didn't think about long term behaviour. Thanks for the correction!

BTW: How about using an LTC2057 then? Its input bias current  and
GBW spec is similar to the LT1012, but its offset voltage and drift
are far superior. Or would its charge injection noise be too large
for this application?

Attila Kinali



-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Allan variance by sine-wave fitting

[Bob kb8tq]

Hi

One of the TimePods that I had access to in the past was particularly good
at telling you it was sitting on top of a power transformer. It didn’t matter a 
lot
which instrument the power transformer was in. For some weird reason it
was a good magnetometer at line frequencies. I never bothered to send it
back for analysis. Simply moving it onto the bench top (rather than stacked 
on top of this or that) would take care of the issue.

As far as I could tell, it was just the one unit that had the issue. None of the
others in the fleet of TimePods seemed to behave this way. Given that they
normally are very good at rejecting all sorts of crud and ground loops, it was 
somewhat odd to see. 

Bob

> On Feb 26, 2018, at 7:13 AM, Tom Van Baak  wrote:
> 
>> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?
> 
> The ADEV wiggles aren't visible with normal tau 1 s measurements. But since 
> the TimePod can go down to tau 1 ms, when I first measure a standard I like 
> to run at that resolution so effects like this show up. Once that's done, 1 
> ms resolution is overkill.
> 
> In this case it appears to be power supply noise. Attached are the ADEV, PN, 
> and TDEV plots.
> 
> The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing 
> at 60 Hz. When integrated these cause the bumps you see in the ADEV plot. 
> It's best seen as a bump at ~4 ms in the TDEV plot.
> 
> Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 Hz.
> 
> /tvb
> <5065a-adev.png><5065a-pn.png><5065a-tdev.png>___
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Re: [time-nuts] Replacement A9 boards for the HP 5065A

[Attila Kinali]

On Sat, 24 Feb 2018 23:44:16 -0500
Charles Steinmetz  wrote:

> Given the relatively low resistances at the op-amp inputs (10k ohms), 
> the ultra-low input "bias" (leakage) current of the 6240 is simply 
> unnecessary.  Any offset due to the input currents (within the general 
> range of any of these op-amps) is insignificant compared to the op-amp's 
> offset voltage.  Thus, offset voltage, offset voltage tempco, and offset 
> voltage long-tem drift are the critical parameters (as Poul-Henning 
> pointed out).  And here, the 1012 is clearly the best of the three.  In 
> addition to having the lowest input offset spec, the 1012 has guaranteed 
> maximum specifications for these important parameters.  The 6240 (for 
> good reason) is *not even rated* for long-term stability (drift). 
> (Long-term offset stability is a particular weakness of CMOS op-amps.)

Oh.. right, I didn't think about long term behaviour. Thanks for the correction!

BTW: How about using an LTC2057 then? Its input bias current  and
GBW spec is similar to the LT1012, but its offset voltage and drift
are far superior. Or would its charge injection noise be too large
for this application?

Attila Kinali



-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

> BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?

The ADEV wiggles aren't visible with normal tau 1 s measurements. But since the 
TimePod can go down to tau 1 ms, when I first measure a standard I like to run 
at that resolution so effects like this show up. Once that's done, 1 ms 
resolution is overkill.

In this case it appears to be power supply noise. Attached are the ADEV, PN, 
and TDEV plots.

The spur at 120 Hz is massive; there's also a bit at 240 Hz; almost nothing at 
60 Hz. When integrated these cause the bumps you see in the ADEV plot. It's 
best seen as a bump at ~4 ms in the TDEV plot.

Note the cute little spur at 137 Hz. Not sure what causes the one at ~3630 Hz.

/tvb
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Re: [time-nuts] Replacement Backup Battery for 5065A?

[Stan]

Thanks for all the suggestions! I think I'll take the conservative approach for 
now and just remove the battery (fortunately it has not leaked!) and run from a 
UPS-backed outlet. If I ever decide I want to reinstall the battery, it would 
be to keep the 5065A "original" and not for real backup purposes since, as has 
already been pointed out, an external backup is preferable for a lot of reasons.

Stan

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Re: [time-nuts] Allan variance by sine-wave fitting

[Attila Kinali]

On Mon, 26 Feb 2018 02:43:04 -0800
"Tom Van Baak"  wrote:

> This note is a follow-up to Ralph Devoe's ADEV posting earlier this month.
> 
> It's a long story but last week I was in the Bay Area with a car full of 
> batteries, BVA and cesium references, hp counters, and a TimePod. I was able 
> to double check Ralph's Digilent-based ADEV device [1] and also to 
> independently measure various frequency standards, including the actual 5065A 
> and 5071A that he used in his experiment.
> 
> For the range of tau where we overlap, his ADEV measurements closely match my 
> ADEV measurements. So that's very good news. His Digilent plot [2] and my 
> TimePod / TimeLab plot are attached.

Nice. Thank you!

BTW: Do you know the cause of the oscillations in the 5065 vs BVA plot?

> I'm sure more will come of his project over time and I hope to make 
> additional measurements using a wider variety of stable / unstable sources, 
> either down there in CA with another clock trip or up here in WA with a clone 
> of his prototype. It would be nice to further validate this wave fitting 
> technique, perhaps uncover and quantify subtle biases that depend on power 
> law noise (or ADC resolution, or sample rate, or sample size, etc.), and also 
> to explore environmental stability of the instrument.

For this, we would need a better understanding of what noise is 
mathematically and how it is affected by various components in
the signal path. But our mathematical description is lacking
at best (we only can descirbe white and 1/f^2 noise properly).


Attila Kinali
-- 
It is upon moral qualities that a society is ultimately founded. All 
the prosperity and technological sophistication in the world is of no 
use without that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson
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Re: [time-nuts] Selling Time and Frequency Equipment Or "just saying"

[Tom Van Baak]

Corby,

Thanks for your informative posting. I concur. Let me add a visual that echoes 
your comments. It's the same plot that I attached in the note about Ralph's 
lab. For those of you who can't view email attachments see [1].

The plot is ADEV of 4 typical lab frequency sources:

- A 5071A in Ralph's lab, on loan from NIST.
- A 5065A Ralph owns, which has some 120 Hz noise, but excellent stability 
beyond tau 1 s.
- The 10 MHz ref out of a Agilent/Keysight 53230A counter (XO or TCXO, not 
sure).
- The 10 MHz ref out of a SRS SG348 signal generator (OCXO option).

Note the difference between the 5065A and the 5071A in the plot. You can see 
why for many experiments a 5065A is preferred. I mean, over a wide range of tau 
it's 4x better. OTOH, if you want to make short-term measurements against a 
cesium standard, by all means turn off the Cs beam and let it free-run. Both 
the 5061A and 5071A make this easy.

/tvb

[1] http://leapsecond.com/tmp/2018b-Ralph-4-adev.png


- Original Message - 
From: 
To: 
Sent: Saturday, February 24, 2018 2:14 PM
Subject: [time-nuts] Selling Time and Frequency Equipment Or "just saying"


> First, full disclosure, I have no vested or financial interest in the
> 5065A he is selling.
> 
> Now the 2816A prefix is the last series built so the most modern.
> The last one I remember on eBay went for OVER $4000.00
> 
> Comparing a 5065A to a Cesium (except maybe a working 5071A for the same
> price)\is worse than Apples and Oranges.
> 
> Ask Bert who got rid of his 5065A years ago because he had a Cesium, he
> regrets that now and just got a new one!
> 
> A 5065A buyer is looking for the best short term stability he can find
> (nominal 1.5X10-13th at 100 Sec)
> Keeping on frequency is easy via GPS comparisons.
> 
> A Cesium buyer want NIST traceable accuracy "out of the box" and never
> (practically) having to adjust the frequency. The Cesium will be worse
> when  compared to the 5065A at shorter Tau even if it has a high
> performance tube.
> 
> Another thing to consider when buying a Cesium is what is the condition
> of the tube. The tube will die, just don't know when. (probably at the
> most inconvenient time!), and lets not ask what a replacement tube costs!
> 
> There is no perceptible wear mechanisms in play for the 5065A (I have
> seen exactly one failed lamp in many years of working on them) Many of
> the first 1968 series built will still perform to specs today.
> 
> So,
> 
> Just saying!
> 
> Cheers,
> 
> Corby

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[time-nuts] Setting time on Z3801A and KS24361

[Hal Murray]

I currently have one each that think it is 13 Jul 1998.  That's ballpark of 
20 years ago.  I assume it's 1024 weeks.  The time of day is good.

Has anybody set their time recently?

I thought I knew how to set the time, but the last time I tried, it didn't 
work.  I have done it in the past, but that was several/many years ago.  I 
think a recent date was rejected.  I'll dig out the exact error message if 
anybody is curious.

I also have a Z3801A that is working correctly.  I assume it has not lost 
internal power since before the magic date and the date-check is on the 
set-path rather than the current-time path.

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Allan variance by sine-wave fitting

[Tom Van Baak]

This note is a follow-up to Ralph Devoe's ADEV posting earlier this month.

It's a long story but last week I was in the Bay Area with a car full of 
batteries, BVA and cesium references, hp counters, and a TimePod. I was able to 
double check Ralph's Digilent-based ADEV device [1] and also to independently 
measure various frequency standards, including the actual 5065A and 5071A that 
he used in his experiment.

For the range of tau where we overlap, his ADEV measurements closely match my 
ADEV measurements. So that's very good news. His Digilent plot [2] and my 
TimePod / TimeLab plot are attached.

Note that his Digilent+Python setup isn't currently set up for continuous or 
short-tau measurement intervals -- plus I didn't have my isolation amplifiers 
-- so we didn't try a *concurrent* Digilent and TimePod measurement.

I'm sure more will come of his project over time and I hope to make additional 
measurements using a wider variety of stable / unstable sources, either down 
there in CA with another clock trip or up here in WA with a clone of his 
prototype. It would be nice to further validate this wave fitting technique, 
perhaps uncover and quantify subtle biases that depend on power law noise (or 
ADC resolution, or sample rate, or sample size, etc.), and also to explore 
environmental stability of the instrument.

I can tell Ralph put a lot of work into this project and I'm pleased he chose 
to share his results with time nuts. I mean, it's not every day that national 
lab or university level projects embrace our little community.

/tvb

[1] http://aip.scitation.org/doi/pdf/10.1063/1.5010140 (PDF)
[2] https://www.febo.com/pipermail/time-nuts/2018-February/108857.html

- Original Message - 
From: "Ralph Devoe" 
To: 
Sent: Monday, February 12, 2018 1:52 PM
Subject: [time-nuts] Allan variance by sine-wave fitting

> I've been comparing the ADEV produced by the sine-wave fitter (discussed
> last November) with that of a counter-based system. See the enclosed plot.
> We ran the test in Leo Hollberg's lab at Stanford, using a 5071a Cesium
> standard and my own 5065a Rubidium standard. Leo first measured the ADEV
> using a Keysight 53230a counter with a 100 second gate time. We then
> substituted the fitter for the counter and took 10,000 points at 20 second
> intervals. The two systems produce the same ADEV all the way down to the
> 5x10(-14) level where (presumably) temperature and pressure variations make
> the Rb wobble around a bit.
> 
> The revised paper has been published online at Rev. Sci. Instr.

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