Re: [time-nuts] HP5065A C-field mods and optical unit mods

[ws at Yahoo via time-nuts]

Corby

 

Just a 1 cent thought that may not apply or be accurate.

 

C-fields are current sensitive, so if they are wound with copper wire, any
small change in their temperature, even when temperature controlled, could
have a effect much greater than 1PPM on that current when driven from a
fixed voltage thru a resistor.

Does anyone use current drive?

 

ws

*

Corby posted:

Attached is the schematic of the C-field supply.

 

Cheers,

 

Corby

 

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Re: [time-nuts] How to test a super Rb standard

[ws at Yahoo via time-nuts]

on Wed, Jan 18, 2017 Chris wrote:
 
>But BEFORE you try and improve the Rb performance you need to have some way
>to MEASURE its performance.  This is likely much harder.
 
 
Testing most RB's mid & long term performance can be done "on the cheap" by
using a Tbolt that's been set up to accept it as an external Oscillator.
With discipline turned off, it uses the GPS directly as the Freq ref to plot
& record the Rb's Phase error over time. 
Can then use TimeLab to do the ADEV etc. plotting from the large saved
LadyHeather's  xx.Log data file.
 
The limit using GPS as the Reference to test a "super RB" is the GPS's
accuracy which I hear is around +- 10ns & ~1e-13 per day when using a good
antenna setup.
 
Attached is a LH and TimeLab plot of a super LPRO RB with ADEV of <1e-13 at
1 day and a pretty consistent freq offset of ~7e-14 over 4 days. 
(This LPRO showed an ageing rate of 2e-15/day over a selected 12 days) 
 
Ws

 

 

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Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

[ws at Yahoo via time-nuts]

If you have a good antenna setup and a constant temperature environment:

The way to get the lowest noise over short time periods on a TBolt is to set
the TC setting as high as you can (typically 500 to 1000+), and set the
Damping factor as fast as you can (typically 0.7 to 1).

The reason is that the Tbolt has a simple basic PI phase lock loop
controller.
The Proportional gain is a function of 1/TC and the Integrator gain is a
function of the damping.
The Problem is that the GPS phase error signal is a noisy thing with short
and long term peak variations of about 10ns. 

Any GPS phase noise is directly fed thru to the Dac output scaled by the "P"
Gain.
With a 10 ns phase noise step and a 100sec TC, the "P" gain will change the
oscillator freq by 1e-10, on the very next one sec Dac update.
This is not done to keep the time correct; it is needed to correct the
Frequency in the desired time constant period.

This then causes the continuous up to 1e-10 freq steps, with the factory
default setting, the effect of which can be seen by plotting the DAC
voltage.
If the TC is made twice as long then the Dac noise step size is 1/2, etc.
If you have a good setup and a low ADEV osc at long time constants, then the
longer the TC, the better the short term Peak freq noise will be.
If you want the "Dac P-gain freq noise" peak to be under 1e-11 then the TC
must be set >1000sec. (which then needs to use the extended TC method)

Where as the Damping setting controls the integrator gain and its effect is
filtered and non linear. A change in damping from say 2.0 to 0.7 will
increase the Dac noise by up to only 25% but reduce the setting time by over
10 to one.


>Bert posted:
>For our work frequency has to be better than 1xE-11 one second.
>Unless someone can help us with settings we will not revisit Tbolt.

The attached shows that a modified Tbolt can do 1 sec freq error of about
1e-11 peak over most of this 2hr run. The 1 sec ADEV of this run was about
1e-12.
Sounds like best to go back to your previous system, because you are not
going to get there by randomly changing the settings.


ws



>> A damping setting in a Tbolt of greater than 2 is not a good idea.

>It is if one is only concerned about frequency stability and accuracy 
>and wants the best performance that can be obtained at tau < about 10 
>seconds.

>> And a TC setting of >1000 is not a good idea unless using the 'extended
>>TC' method.
>I did not suggest setting the TC >1000. 

>Best regards,
>Charles

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Re: [time-nuts] Lady Heather's Tbolt oscillator auto-tune function

[ws at Yahoo via time-nuts]

A cold oven freq is off by hundred's by Hz, Much much greater than the range
of the Dac
The TBolt does not start tuning until it's oven has warmed up.
Setting anything in the Tbolt biased on cold start turn-on is counter
productive. It takes days or weeks for it settle down.
At initial turn-on and when returning from a lost signal drop-out if the
phase is off, the Tbolts enters a fast Dac slue tune mode that sets the
phase and then the Freq to zero cross before entering its normal mode. 
Because of these, it does not mater in the least what the Dac is set to at a
cold start.
A damping setting in a Tbolt of greater than 2 is not a good idea.
And a TC setting of >1000 is not a good idea unless using the 'extended TC'
mode.
. . .



ws
 
*  

>> Actually, for best results from a cold start, it is best to set the
initial DAC voltage to whatever voltage produces 10.0 MHz *when the
oven is cold*.

Bob replied:

> .. errr . that's pretty far off :) DAC at 10 or 20 minutes is probably the
target.

No, DAC for 10.0 MHz with a stone cold oven is best for cold 
starts.  This setting is still best even if the oven is partly warm, 
because the loop is moving the DAC in the same direction it needs to go 
-- it can "catch up" gracefully without racing in the wrong direction in 
full saturation to meet the crystal as it warms up, then banging back 
and forth from saturation in one direction to saturation in the other 
direction before finally leveling out.  It is the damped oscillatory 
approach to the capture zone, and recovering from saturation (not just 
once, but multiple times), that slows things down.

By starting the DAC to produce 10.0 MHz from the cold oven, all 
that is avoided and the loop just tracks the warming crystal (or, if it 
can't quite keep up, at least it is moving in the same direction and can 
catch up gracefully without overshoot -- still much faster than starting 
from the DAC voltage that produces 10.0 MHz with a fully warm oven).

Trust me, I tried all of this experimentally and know whereof I speak.

Best regards,

Charles




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Re: [time-nuts] Tbolt issues

[ws at Yahoo via time-nuts]

Bert 
a) 1e-10 freq error, Sounds to me like you have a typical TBolt with near
factory default setting. 
The most important thing to get good Tbolt frequency performance is the
antenna, with good sky view and correct location setting. 

After that there are some 'basic' Tbolt setting and things that can be done
that will get it close to the best, within say 2 to one.

 
Other comments in text below and attached graph.


***
Bert Kehren wrote in part:
 
>would you mind sharing 1 second frequency data that you get out of the
>tbolt to get an idea what is possible. 
>Looks like we are not the only ones trying to improve frequency performance
>and hopefully some will share settings.
>For us it is absolute Frequency, to me it is a measure of true
>performance.

 a)Attached is data plotted from a modified Tbolt that has a 1 sec ADEV of
1e-12. 
This shows that its 100ms "instantaneous" freq error varies from 1 to 3e-11.
As long the frequency counter is not resolution limited, the 0.1sec, 1sec,
10sec, and 100 sec sampled plots all had about the same peak to peak freq
error just with less high freq fuzz, 

***
>Tbolt is an excellent time device but not good for frequency reference 
> past 1E-10 because the frequency is constantly changed to correct time. 
 
a) The Tbolts damping setting is what controls how much 'freq noise' is
added to correct for time error (i.e. Phase error).

You can set it to optimize whatever you want.
Many time-nuts use Phase error, not frequency error as the indicator of
performance, so I tend to set the damping low to minimize the phase error.
When the gain is set correct, damping of 0.707 gives ideal critical damped
phase error correction response. 
A damping of 1.2 gives a nice compromise for frequency response correction.


A damping of 0.7 adds ~25% freq overshoot noise and gives you the lowest
phase error.

A damping of 1.0 adds ~10% freq overshoot noise and any time/phase error
takes about 3 times longer to correct.

A damping of 1.25 adds <5% freq overshoot noise and the time error takes ~6
times longer to correct.

With a damping setting of 2, less that 1% of freq noise is added to correct
for time errors and phase errors takes >>10 longer to correct.

With a damping of >=10, the time correcting is so slow that time/phase
correction can take days, and there is *no* added freq noise.


***
>With the popularity of the Tbolt an analog or digital clean up loop would
make sense. 
>My Swiss partner Juerg has relied on an OSA F3 for Tbolt clean up but has
had continuous bad results . 
>The result is that the OSA F3 does not clean up the Tbolt and we see
+-4E-11 changes and old data shows even some +-8E-11 excursions. 
 
a) The Tbolt control loop is already a clean up controller, it is cleaning
up the noisy GPS freq signal.
What I have found is that with a properly setup TBolt, an addition clean up
Osc does not help to give better low frequency stability because the peak to
peak noise output is pretty much constant whether the cleanup bandwidth is
set at 0.1sec, 1sec, 10sec, 30sec or 100 sec.
And of course you'd need a cleanup oscillator that is more stable that the
Tbolt over the cleanup time period.
If you have the low noise clean up oscillator, what works better is let the
Tbolt discipline it directly as an external oscillator.
 

ws



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Re: [time-nuts] GENIUS by Stephen Hawking (PBS TV),

[ws at Yahoo via time-nuts]

Tom 
Impressive. Nice job.

How would one go about to prove beyond a doubt in that experiment that 18ns
of phase shift in 24 hrs was truly caused by freq offset due to Relativity
and not by some other combination of environment and handling issues that
effected phase &/or freq once the identical clocks where separated and
operating at different temperatures, pressures, elevations, vibration, tilt
angles, power supply voltages, airflow, cosmic rays, ozone, or some other
unmeasured things that may be effecting the results?

To increase  *gravity* a lot more than a 7,000 ft altitude change, and
without changing the environment variables, could one set of the CS clocks
be put on a centrifuge, such as a fast spinning merry-go-round at a local
park?

Anyone know what the 2G turn over effect, TC, etc, is of portable CS
standards? Ideally they should all be zero, but probable aren't.

ws 

 

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Re: [time-nuts] Trimble Thunderbolt error

[ws at Yahoo via time-nuts]

 
Same here for me in central California near the coast(SLO county).
My Tbolt lost all satellites all at the same time, for 100 min @ ~5:30 PM
PST.
Then just as suddenly all came back on line, with no input from me.
A truly unique experience for this Tbolt which runs pretty much
continuously.
LH screen shot attached.  
 
ws
 
*
 
Hello Group, 
 
A friend about 2Km up the road from me and I both run the Trimble
Thunderbolt GPSDO. For a few years now they have both worked flawlessly.
Around 1/2 an hour ago ( I wasn't in front of mine when it happened ) at
roughly 00:45 UTC the Mates went into "holdover" mode and reported "no
Sats". I have just checked mine and it is reporting the same.. 
 
I am wondering if anyone else has had this happen to them today ? 
 
Cheers, 
 
Rob. 
 
 

 

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Re: [time-nuts] HP 10811

[ws at Yahoo via time-nuts]

The 10811 units I've measured use slightly different circuits for their
internal ovens.
The single version has a 10V internal regulator for it's temperature
controller, the Dual unit has a 5 V reg. The thermistor bridge voltage is 5
volts on both units.
The standard unit's oven start to come out of regulation at around 16V, the
Dual oven at around 10 volts. For best control I run them minimum at a few
volts above those values. I think the min spec is something like 20V on the
single and 12V on the dual oven units. 
So On the dual oven units, The inner, outer and Osc can all be run from 12V.
But if you want nut performance, best not to use the same supply for them. 
I start with a 15V supply, so that there is no interaction between circuits.

ws


*
From: Richard (Rick) Subject: Re: [time-nuts] HP 10811

On 2/11/2016 2:56 PM, ws at Yahoo via time-nuts wrote:
> Joe
>
> The inner oven voltage needs to be stable! To better than 0.1V.
> Unlike the single oven unit, the inner oven on the dual oven unit runs
fine
> at 15 Volts. It draws a couple hundred ma after warm-up.
>

It's been a long time, but IIRC, it was common knowledge
within HP that the standard 10811 oven will run on 15 Volts,
but it just takes longer to warm up.  The most extreme
example was the 5334A, which had such a bogus power supply
design that the voltage sagged to +12V during warmup.
Now the oven won't work correctly on only 12V, but it
will work to the extent that it warms itself up.  Once
the current cuts back, the voltage goes back up to over
15V and it works fine.  When I started the 5334B project,
the power supply was the first thing to get redesigned.

Rick N6RK

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Re: [time-nuts] HP 10811

[ws at Yahoo via time-nuts]

Joe

The inner oven voltage needs to be stable! To better than 0.1V.
Unlike the single oven unit, the inner oven on the dual oven unit runs fine
at 15 Volts. It draws a couple hundred ma after warm-up.


One thing that improves the performance of a dual oven 10811 when being used
in a standalone application is to add a linear temperature controller for
it's the outer oven.
This makes the TC frequency change around a hundred times less sensitive to
room temperature variations, and by doing this it also so makes the answers
to your other questions about how best to box it up, a simple "it doesn't
matter", once the outer oven's temperature is set so the heater runs at a
nominal 5 to 6 Volts.

Another thing that can greatly simplify things and improve performance is to
keep the EFC voltage near zero volts and limit the range to 100mv or so
(~1e-8 freq change at 1Hz /Volt).

One of the more important ways to get great performance is by selection.
Many parameters will vary ten to one, and some things can vary as much as
100 or 1000 to 1 between units.

Here is the list of things I do to make a HP10811 dual oven oscillator into
a time-Nut quality stand alone Reference.

1) Select a unit with an ADEV of under 1e-12 from a 0.1 to 10 sec.
(about 1/3 of the ones I've tested)
2) Buffer the 10Mhz output
3) Use a linear 10V outer oven controller
4) Run-in until the ageing rate stabilizes, hopefully at under 1e-11 / day
 If not achieved after 6 months, re-start at #1 above.
5) Mount it on or near it's zero tilt axes
6) Run the oscillator's circuit on a *stable* low noise 12V supply
7) Run the inner oven on a stable and liner 15V supply
8) Rewire the inside. Besides removing ground drop problems, it also allows:
  a) Unseal the internal tuning nut by loosing it ~ 1/2 turn
  b) Readjust the mechanical freq, so the 10 MHz is within 1e-9 with the EFC
at zero. If retune is necessary then repeat step 4 above.
9) Connect the EFC to the wiper of a 10 Turn dial pot. Its range set to give
a freq change of 1e-8 full-scale (~100mv)(1e-11 / division).
10) Power the whole thing up with a stable, low drift, low noise, 15V, 2A
linear power supply. 
11) Leave it powered up, and running from an uninterruptible power source
12) Check and plot the absolute freq drift long term with a Tbolt GPSDO 
13) Check its short term freq with a TPLL.
14) Keep it away from any AC line noise sources, especially things with
transformers in them. 


Short Comment about rewiring inside at

a Picture at



ws
  
*

Joseph Gray Posted:

I have a spare 10811 that I want to setup as a standalone reference.
Since it is a double oven unit, should I put it and the power supply
in just a single walled plastic or metal box? Should I make air vents
or not? Going to extremes, can I put the OCXO inside a thick Styrofoam
box with no air flow at all (power supply external), or will this
cause overheating?

I may do a battery and float charger arrangement for the power supply,
so I can keep it running if the lights go out, or I want to take it
portable.

I know that the oscillator voltage needs to be very clean and stable,
but how about the oven voltage? Can I get away with a nominal 24VDC
from a battery, even while it discharges?

BTW, in case anyone was wondering why I haven't been on the list much
for quite a while, I have been busy taking care of my elderly mother.
She passed a month ago and now I am getting involved in projects
again. The first project is to clean and rearrange my work room. No
need to clutter the list with messages of sympathy. I'll pretend that
you sent them :-)

The 10811 has been on the shelf for a while, so once I get it running
again, I'll let it age for weeks (if not months) before adjusting it.
One advantage of being otherwise tied up lately, is that I have some
14-pin DIP Micro Crystal OCXO's that have been powered for months on a
breadboard, waiting for me to use one in a project. They should be
nicely aged by the time I get around to them.

Joe Gray
W5JG



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Re: [time-nuts] Looking for Z3801 OCXO

[ws at Yahoo via time-nuts]

 

John

If it is off very far the first thing I'd suspect is the inner oven.

 

Assuming the freq is still stable and low noise, one option is to rewire it,
and make the freq adjustment accessible.

Removing the original inner wiring wrap also provides many other advantages,
and no down side that I've found.

After modifying several, it now takes me about an hour to do. 

>From the outside you can not tell that it has been modified, unless I change
the crappy little blue shielded RF and EFC cables that it originally comes
with, which I now always do. 

It takes about five minutes on a correctly modified unit to readjust the
frequency. The adjuster nut and hole is accessible after temporarily
removing the bottom outer cover, thru a 3/8 inch access hole drilled in the
bottom of the outer oven that is placed *under* the bottom heater flap. 

It is easy to adjust thru the bottom of the unit and can be done without
powering down or disturbing the oscillator or either oven's power.

 

Picture attached of modified inside cabling, before the two shielded cables
are added.

No mess. Any goo gets cleaned up with alcohol or thrown away.

 

ws

 

 



John Posted:

"Looking for Z3801 OCXO"

 

I have a Z3801A whose oscillator has aged out of correction range, and 

thus throws an EFC alarm.

 

Anyone have a still-in-range double-oven HP10811 from a unit that died 

for another reason?  If so, I'd be happy to acquire it.

 

(I tried disassembling one of the double-oven 10811s years ago and found 

that extracting the oscillator can from the outer oven, heater, and 

gooey insulation made such a mess that it would be impossible to 

reassemble.)

 

Thanks!

 

John

 

 

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Re: [time-nuts] Morion MV89A position

[ws at Yahoo]

Paul
The MV89 is a double oven unit, and assuming it is setup and working correctly, 
 it's sensitivity to thermo capacity, external temperature effects, sweep spot, 
and all the other nutty stuff, is Way below the MV89's noise level which is 
generally under 2e-12 when just setting on a bench in the open. 
(as long as you do not move or tilt it)
All the stuff that is being talked about can effect single oven units. 
The main purpose of the outer dual oven units, is to isolate the freq change 
from these effects, and on the several MV89's I tested, 
it's outer oven works very good and the unit does not need any special 
mechanical considerations to improve it's stability.

Your test data, that shows such high ADEV  values is most likely your tester's 
resolution, assuming you have a clean electrical setup.
If your tester does not have at least 1ps (1e-12 seconds) resolution, which few 
do, then your tester is limiting the ADEV at 1 second.
From your data, it looks like your tester is very likely the problem up to at 
least a couple hundred seconds.

In summery, looks like you need a better tester if you want to do any valid 
performance testing below ~1000 seconds on a typical MV89.

ws

***
Paul A. Cianciolo paulc at net.net 
Tue Jan 28 22:53:38 EST 2014 

Charles,

Thank you for the information and I apologize for responding late.
I understand the concept of the sweet spot. I made the changes you
mentioned isolate the OCXO thermally from the chasiss.
It is out of the Dewar and sitting on a piece Styrofoam.  It is then mounted
in a chassis that 19 wide 19 deep and 5 or so high.
Sure enough after I made the changes the,  ADev on time lab shows at 2 sec.
all the way up to 3600 sec.
With a sample rate of Hz dictated by the 1 PPS out of the thunder bolt the
reading are below

 2 sec.  1.79 -10,   
20 sec  1.95 -11
200 sec 6.83 - 12
1000 sec 1.70 --12

Can you mention the size of the aluminum box you are using to add thermal
capacitance?
I am very interested to try and improve my results

Thank you


Paul A. Cianciolo
W1VLF




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Re: [time-nuts] Lady Heather numbers

[ws at Yahoo]

Garren posted  

I notice that whenever a satellite drops out
it causes the oscillator white trace and the DAC green trace to jump around. 
 I wonder why that happens when there are 6 other good satellites.

The main causes of this is a poor location setting,  (do a 24 + hr survey)
or the TBolt is using data from some multipath satellite signals. 

To get more info on how your antenna is doing, can do a 24hr + signal strength 
plot (SAS) 
To see more about your units performance, can change your display time from 1 
min / div  (17 min FS) to about 3 days full scale. ~(D360)
I typically use 1 day / division for longer term displays (have to change the 
default 3days of data logging to 30 days)

ws
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Re: [time-nuts] Thunderbolt mounting

[ws at Yahoo]

I second that, when done correctly, it works great. But there are all kinds of 
ways to do it poorly.

First off, 
What the TBolt is best for is to provide great long term frequency stability 
that can be better than a Rb or Cs. 
If you want a low phase noise signal without spurs, 
Don't use the Tbolt's output directly, use the TBolt to discipline an external 
low noise oscillator. 
 
The TBolt's perform can be made even better, by reducing the excess noise that 
it's control loop adds to the OCXO.
Any noise on the DAC out, that is at a frequency higher than the control loop 
Bandwidth is adding noise to the Osc, not reducing it.

the basic steps needed to make the TBolt as good as it can be, listed in 
reverse order of importance are:

1) Increase the control loop time constant.  The 100 second default gives poor 
performance for a well setup TBolt.
I find 2000 sec, using the extended TC method is about right for my stock unit.
To be able to use that long of a TC, both the Antenna system and environment 
must be made near perfect.

2)  Set the Tbolt up to be insensitive to changing room temperature
The desired goal being not to let any part of the TB's case change temperature 
over ANY time period.
Several different ways this can be done, each with it's own set of compromises. 
The simplest, cheapest, safest, smallest and best performing way I have found 
is;
http://www.febo.com/pipermail/time-nuts/attachments/20120712/9aa84ffa/attachment-0001.jpg


3) Get a good antenna system with a good view of the sky and set the elevation 
low enough so that there is always at least 4 or 5  satellites being used, but 
still high enough not to see any sat signal that is below about 40dBm, or that 
has any reflections in it.
I find 15-20 deg works best for my location.


4) Use a good stable power supply that does not add any low freq Osc noise.
Obviously if the TBolt is bein g powered from a power supply that is jumping 
around due to fan switching, temperature changes or anything else, It is being 
done way wrong.  
BTW, The Tbolt is much less sensitive to changes on the -12, so if you do not 
want to properly isolate the + supply, use the -12 volts for the Temperature 
controller power.

ws

***
Nope,  if implemented properly it works VERY well.   No ADEV humps,  no 
vibration induced spurs,  no commutator EMI,  no power supply garbage.   

Lady Heather's PID PWMs the fan to control the speed.  It is not a bang-bang 
controller.   You should baffle the air flow so that it does not impinge 
directly on the unit.  I have the tbolt sitting on a piece of waffle foam in 
the box...  gives very good vibration isolation,  but even without it I saw no 
fan related noise/spurs.   Proper power supply filtering for the fan power 
might be useful,  but I see no coupling on mine.

As the Wise Man said...  one experiment is worth 1000 opinions.

-
Sorry guys, but using a fan on a thunderbolt is nuts. Not time nuts.  
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Re: [time-nuts] Lady Heather

[ws at Yahoo]

Don

no internal connection needed.
Lots of ways to do it,
an isolated optical isolator connect to a couple of pins on the RS232 
connector is one way.


The LH controller can also be used to just Heat for those that don't like 
moving parts,

or dual with heat and cool as well as just drive a fan.
If ypu want you could go full nuts and connect it up to control the room 
AC/Heater


For the LH driver I use and how I use it see:
http://www.febo.com/pipermail/time-nuts/attachments/20110116/76cc81b5/attachment-0001.jpg

text at:
http://www.febo.com/pipermail/time-nuts/2011-January/053648.html

ws

***

[time-nuts] Lady Heather
Don Latham djl at montana.com

Hi: Been following the latest Thunderbolt thread a littlt more closely
than previous ones. Mention was made of Lady Heather driving a fan with
PID. I looked at the LH website and what I have for tbolts. Where is the
fan control physically hooked? An internal mod? I admit I may have
allowed this info to pass by in the past...
Don



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Re: [time-nuts] Lady Heather

[ws at Yahoo]

Don

No, it is not bang-bang. Look at the plot results.
You don't get .001 deg type resolution and control with a bang-bang controller.

It is a full Linear, universal,  PID + with self tuning capability. 
The output is a high resolution Linear PWM driving one of the RS232 pins and a 
polarity/enable 
output on one of the other pins which can be used for heating / cooling / 
enable / fail_ save, etc.
( I don't use the second output with the KISS simple fan driver, because that 
hardware is already fail-safe).

The PID can be manually set for all kinds of things, Including Band-Bang 
control.

ws




Thanks, Warren, for the refresh. So the L.H. fan control signal is
bang-bang, and not really a PID, as it's on the DTR data line.
Don

ws at Yahoo
 Don

 no internal connection needed.
 Lots of ways to do it,
 an isolated optical isolator connect to a couple of pins on the RS232
 connector is one way.

 The LH controller can also be used to just Heat for those that don't
 like
 moving parts,
 or dual with heat and cool as well as just drive a fan.
 If ypu want you could go full nuts and connect it up to control the room
 AC/Heater

 For the LH driver I use and how I use it see:
 http://www.febo.com/pipermail/time-nuts/attachments/20110116/76cc81b5/attachment-0001.jpg

 text at:
 http://www.febo.com/pipermail/time-nuts/2011-January/053648.html

 ws

 ***
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Re: [time-nuts] Lady Heather

[ws at Yahoo]

Yes, RTS is the other pin. 
From 'Heather.txt'  {Helper} file

Added ability to actively stabilize the device temperature. 
(/TT=degrees or TT command line option).
Uses the serial port RTS and DTR lines.  
RTS is the temperature controller enable (+12=off, -12=on)
DTR is the heat (-12V) / cool (+12V) line. 

ws

**

So the other signal is on pin 7, RTS?
Don

*
ws at Yahoo
 Don

 No, it is not bang-bang. Look at the plot results.
 You don't get .001 deg type resolution and control with a bang-bang
 controller.

 It is a full Linear, universal,  PID + with self tuning capability.
 The output is a high resolution Linear PWM driving one of the RS232 pins
 and a polarity/enable
 output on one of the other pins which can be used for heating / cooling
 / enable / fail_ save, etc.
 ( I don't use the second output with the KISS simple fan driver, because
 that hardware is already fail-safe).

 The PID can be manually set for all kinds of things, Including Band-Bang
 control.

 ws


 

 Thanks, Warren, for the refresh. So the L.H. fan control signal is
 bang-bang, and not really a PID, as it's on the DTR data line.
 Don

 ws at Yahoo
 Don

 no internal connection needed.
 Lots of ways to do it,
 an isolated optical isolator connect to a couple of pins on the RS232
 connector is one way.

 The LH controller can also be used to just Heat for those that don't
 like moving parts, or dual with heat and cool as well as just drive a fan.
 If ypu want you could go full nuts and connect it up to control the
 room AC/Heater

 For the LH driver I use and how I use it see:
 http://www.febo.com/pipermail/time-nuts/attachments/20110116/76cc81b5/attachment-0001.jpg

 text at:
 http://www.febo.com/pipermail/time-nuts/2011-January/053648.html

 ws

 ***
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Re: [time-nuts] Interesting paper: Don't GPSD' your Rb...

[ws at Yahoo]

Poul

I agree, 1PPS from many GPS engines, if sawtooth correction is not used, can 
add all sorts of errors like hanging bridges.
Some can sound really bad, like non zero bias over short or very long time 
periods and 12 ns of early or late wonder.
It's interesting to talk about these problems, But from a practical point 
you do not need to fix them, because all these errors are small compared to 
what the errors are from the received GPS signal including it's short term 
wonder and long term near 12 and 24 hour cycles due to satellite orbits 
cycles.


If you want something without the1 PPS problems, can use an optimized tuned 
Tbolt.


ws

*
From: Poul-Henning Kamp


I don't understand that.  What am I missing?


You are missing that the average of the 1PPS pulse only can be trusted
to be zero over a timescale of many hours.

This is an error-source distinct from GPS reception, caused by the
picking a preexisting flank nearest to the epoch, with no attempt
to keep the average of the resulting error zero.

Imagine that the GPS receivers clock happens to run on perfect
frequency for a while:  That means that the flank used to generate
the PPS will have a fixed location relative to the epoch, for instance
always 12 nanoseconds early or late.

I belive that some GPS receivers have deliberately de-tuned Xtals
for this very reason, but unfortunately that is only a partial
fix, as the problem is a modulus-issue, so not only is perfect
frequency bad, but perfect +/- n Hz is equally bad.

The hanging bridges Tom has plots of on leapsecond.com, arises when
the frequency of the GPS xtal changes.

At one point I tried putting a 1W resister close to the xtal and
feed it with a very slow sine-wave to see if jittering it would
get me an average of zero of shorter timespans.  My experiment
was inconclusive, but the idea is not unsound.

Poul-Henning Kamp




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Re: [time-nuts] Interesting paper: Don't GPSD' your Rb...

[ws at Yahoo]

Thanks, Poul
If that was their point then, I missed it completely.
The way I read it, I think you are giving them WAY too much credit about 
them understanding subtle things like that.


Yes we do agree that using low accuracy 1PPS signals can cause some 
unforeseen problems.
They are using 10 MHz for the Rb loop, so the 1PPS problems do not apply 
(much).
But note there is still the same approx 1PPS concerns even if the hanging 
bride things are filtered with a OCXO, 1PPS GPSDO.


A 1PPS signal with hanging bridges has a higher ADEV noise level so if used 
for disiplinng ANYTHING, the loop needs to be set a lot slower.

First order, it is about as basic as that.

If disciplining a low end Rb where temperature change causes the majority of 
the errors, then need the Rb loop time constant to be in the one or two Hour 
range.

If using a supper RB then the loop can be up to one or two days.
Like has been stated many times before, the discipline loop constant is 
(mostly) determined by the ADEV cross-over point between the Rb used and the 
GPS engine used.


One of the things I noticed is that their check data was plotted at ONLY one 
point per day.
That fact alone makes the details of the actual Rb, the GPS engine, and the 
disciplined loop of VERY minor importance.
Most any reasonable loop or Rb would give about the same results if that is 
the only data points considered.


ws

***

Poul-Henning Kamp said:

In message WarrenS writes:

Magnus wrote:



This is not a paper about Don't  GPSD your RB, as the nut subject line
suggest.


Actually, that is their point, or maybe more specifically:  Don't GPSDO
it the way we do with OCXOs.

At least as I read the paper.

It chimes pretty well with my own experiments and measurements.

The short term noise and offsets of GPS-PPS signals in most cases
is quite detrimal to disciplining a Rb.

Case in point:  Oncore + PRS10.

If you do not apply the negative sawtooth, there is no guarantee
that the PPS signals average will be coincident with the epoch the
receiver tries to mark.

Tom has some plots of the hanging bridges you will experience
and they can have durations so long that it starts to leak through
the PLL steering the Rb, thereby ruining the result.

This is the reason why you need to configure a PRS10 with a
timeconstant a fair bit shorter than theory predicts if you
just hook it up to a GPS-PPS signal.

Interestingly enough, applying the PRS10's 1/256th filter makes
worst case behaviour worse, because the filter makes the PRS10
latch onto even shorter hanging bridges.

If you cannot apply the negative sawtooth, you will get better
results by disciplining almost any random quartz xtal, ovenized
or not to the GPS, divide it down to PPS and then discipline
the PRS10 to that.

I belive that is the same thing the paper advocates, although
they communicate it very badly.


--
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
phk at 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] Question about precise frequency / phase measurement

[ws at Yahoo]

No page. The effect is nothing very special. No relativity.
Mostly just the effect of the oscillator's G sensitivity caused by tilting 
and acceleration as it swings.

What is generally measured with a 2 G static turn over test.
The thing about the test is that it gives a signal that is very hard to 
measure and a wave form shape that is easy to verify.
This shows how good the TPLL is at detecting small frequency changes very 
quickly.
The TPLL2.0 gives the best results for that test that I've seen from any 
instrument.


ws


On 2012/04/20 13:44, time-nuts-request at febo.com wrote:
For a high end example showing external influences causing small freq 
variation, see the swinging OSC test  at

http://www.thegleam.com/ke5fx/tpll/swing.gif


Neat!  Is there a page explaining a bit more about it?

I was summarizing the Hafele-Keating experiment to my brother the other 
day -- 
just bullshitting, really, 'cause I barely know what's going on here 
myself -- 
so it occurs to me to wonder.  Acceleration is probably the cause, but a
mechanical effect in the oscillator, something tightened in cockpit? 
Surely
not a relativistic effect.  Not at 18 inches.  (This is where we figure out 
that
I grasp the concepts, but can't actually do the problems.) 



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Re: [time-nuts] Update on Rb Performance

[ws at Yahoo]

John

If you have the raw phase data, can you post a plot of what the well 
filtered freq offset looks like over that 10 day period?
I've have found a properly filtered high resolution freq vs. time plot 
provides a lot more useful information than the couple of data numbers of a 
ADEV plot for evaluating long term performance of an Osc and helps separate 
all the many different possible causes of  poor ADEV numbers.
This is because then one can see the shape and magnitude of the Freq drift, 
therefore being able to see if the freq drift has a short term cycle due to 
temperature or if it is linear due to ageing or 2nd order due to still 
stabilizing or if it contains freq jumps due to 1/f flicker, or a single 
large jump due ...etc,  etc.
To be of any long term use, the freq data must be filtered over a long 
enough time period, such as a 1 hr running averaged, so the plot is more 
than just the 1 sec noise shown on most freq plots.
The big avantage of using long term freq plot instead of a ADEV plot is the 
freq error is not noise but sytimatic errors which I have found to generally 
be the casse over longer time periods, then 10days worth of data can be use 
to prdict the what the future performance will be, compart that to what 
10days of ADEV give, a lot of uncetaiy to even prdict what the one day drift 
will ber.if the Noise is not noise but due to Using a 10 day

ws


John Ackermann N8UR jra at febo.com

This isn't the real long-term stability test I'm planning to do, but I
did let the measurement continue on the last unit I was testing (an
Efratrom FRS-type) out to 10+ days, which should give fairly reasonable
data out to 100K seconds.  An ADEV plot is attached.  I would ignore the
last two plot points as there isn't enough data for them to be very
meaningful.

Bottom line is that Efratom specs the FRS units at 1e-10/day, and this
one seems to do more than an order of magnitude better.  But also looks
like you need a lot more than 10 days data to draw any real conclusions;
you can look at this plot and think that the ADEV is maybe heading back
down after a peak near 1e-11.

John 



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Re: [time-nuts] Testing a LPRO RB

[ws at Yahoo]

The other way to get around the inaction of the temperature effects and 
drift effects to start and stop the displayed plot at the same temperature 
and more important is do the ageing ageing rate over a an multiple of 
complete temp cycles which is why that plot is exactly 7 days long. giving 7 
full temp cycles.


I've not yet figured out how to get LH to give accurate TempCo number, so I 
do it the way I described by line up plots

ws.

**

[time-nuts] Testing a LPRO RB
Mark Sims holrum at hotmail.com

Lady Heather's osc drift rate calculation does assume that the temperature 
has been stabilized.   John DuBois and I did quite a bit of work to find a 
way to unwind the osc parameters from the available unstabilized reported 
data using SciLab on the log files,  but nothing seemed to work reliably. 
Generally the data analysis croaked because of things like noise and matrix 
singularities.


Also,  if you do stabilize the temperature,  it is very easy to get the osc 
tempco.   Just turn off the stabilization and see how the osc drifts as it 
warms up. 



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Re: [time-nuts] Low-Cost Rubidium Performance

[ws at Yahoo]

ADEV and friends was invented and most useful to better characterized and 
compared oscillators.
To make any meaningful comparison test, the results MUST be reproducible to 
some level.
Errors bands are there to show what the reproducible level is, but 
unfortunately the error bands do not include temperature effects and other 
systematic error causes.
You can of course use the ADEV math function for anything, but MY definition 
of true and accurate ADEV numbers must include a set up that gives 
repeatable results.
If you test is done over different or unknown temperature changes that have 
major effects, then I'm calling that poor ADEV data (taking).


previously posted The only issue I see is it may make fair comparison 
difficult, unless units are compared under identical conditions.
And IMHO making a Fair comparison is what true ADEV should be for, and 
when it does not do that, it becomes nothing much more than a useless number 
generator.


The fact that poor ADEV answers can be used as a random number generator or 
as a tool to misrepresent performance is not the fault of ADEV, but the 
user.


ws

*
John Miles jmiles at pop.net

Indeed,  ADEV is for random freq variation not easily measured by other 
means.


Well, no, ADEV is the two-sample deviation of fractional frequency
differences over time.  That's really all you can say about it.  There's not
really any such thing as true ADEV -- a measurement either meets the
mathematical criteria for Allan deviation, or it doesn't.


Temperature fluctuations do not cause random freq changes and the
temperature's effect should be removed if one wants accurate long term
ADEV numbers.


No, accurate ADEV numbers are whatever you see on an accurate ADEV plot. :)

If I measure two sources in the same environment and I see HVAC ripple on
one ADEV trace but not on the other, then that may be useful information, or
even the only information I care about.   (Of course, it's only useful if
the bin density is high enough to show the effect in question, but that's
not the fault of the ADEV metric itself.)

If you don't want to observe the effect of temperature fluctuations on your
DUT, random or otherwise, the correct solution is not to use a different
metric or to tweak the data, but to shield the DUT against the temperature
variations in question.

Even daily diurnal cycles due to temperature can have major negative 
effect

on ADEV numbers as low as 2000 to 3000 seconds,


Your bin density may be insufficient in that case.  ADEV is not unlike an
FFT in that regard -- the denser the bins, the higher the resolution,
subject to limitations imposed by the window transfer function.  (Enrico
Rubiola has suggested that we should have been using FFT-like measures for
long term stability all along, instead of ADEV.)

It's true that the ADEV function is not all that sharp, but you shouldn't
ordinarily see effects removed from their causes by a 40:1 tau ratio.  IMHO,
if you are seeing significant degradation at the 2000-second level caused by
diurnal cycles at the 12-hour level, something may be wrong.

Outliers are another matter, due to the infinite ringing that a step
function causes.  They should be removed from ADEV and considered as a
separate source of error.  Transients cause some pretty horrible effects in
FFTs as well, regardless of the window characteristics.  Offhand, I can't
think of any simple frequency-stability metrics that are good at ignoring
outliers, and I'm not sure it'd be a good thing if we were to invent one.


and if there is an Heater or AC cycling, then any ADEV numbers about a few
hundred seconds can be due to TempCoeff, which should not be measured
with ADEV or included in ADEV plots.


Again, fractional frequency differences are fractional frequency
differences.  ADEV will show temperature effects, as will an FFT or most
other metrics worth using.  If you don't want to see these effects, you need
to take the appropriate measures to fix the environment, the DUT, the
instrumentation, or all of the above.


This is much the same as a single outlier data point that can screw up the
whole ADEV plot and make it pretty much meaningless and unrepeatable.
Ditto for linear ageing, Should be remove first if one wants true ADEV 
plots.


Linear drift is a good thing to take out... *if* you explicitly want to
exclude it from your observation of fractional frequency-difference
statistics.  Maybe you consider drift or aging to be a valid part of the
statistics you're collecting.  If so, leave it in.  Maybe you plan to
discipline the DUT in a way that will remove drift and aging.  If so, remove
it.  You're going to get a valid measurement of ADEV either way... but
determining whether ADEV is really the best metric to use, and interpreting
it in light of your application, is always up to you.

-- john 



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Re: [time-nuts] Low-Cost Rubidium Performance

[ws at Yahoo]

Right all those things need to be controlled if doing high end nut-testing.

Most time nuts already know enough not to shake their Osc or tweak its Power 
supply etc when  taking ADEV data.
What is often left as the major error source (that can most easily be 
controlled) with a careful setup is delta temperature.
and most also know that temperature needs to be controlled in some way 
especially when getting the most from say a GPSDO.


ws

**
[time-nuts] Low-Cost Rubidium Performance
Mike S mikes at flatsurface.com



You can of course use the ADEV math function for anything, but MY
definition of true and accurate ADEV numbers must include a set up
that gives repeatable results.
If you test is done over different or unknown temperature changes that
have major effects, then I'm calling that poor ADEV data (taking).


Then you had better control acceleration (gravity/shock/vibration),
voltages, humidity, pressure, electromagnetic fields, et al, if you want
validity. Again, what makes temperature a unique case? 



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Re: [time-nuts] FE-5680A Results so far

[ws at Yahoo]

Chris posted:

So how to test it?  anyone have any creative ideas?


That's easy, get a couple more of them.
The using a scope, trigger on one unit and watch the phase drift of the 
others.
With most basic scopes you can detect sub ns phase changes of 10MHz signals 
this way, which allows you to see a 1e-11 frequency difference in a couple 
minutes. (1ns/sec change = 1e-9 freq offset)


Or you could use the basic x y display and count how many minutes it takes 
to complete one cycle.
That will allow you to see the same resolution after a few hours. (a 100ns 
cycle per sec = 1e-7 freq offset)


ws


*

[time-nuts] FE-5680A Results so far
Chris Albertson albertson.chris at gmail.com
Wed Dec 28 18:21:54 UTC 2011

Just got my fe5680 yesterday.   Seems to work but the fe5680 is the most
accurate reference I have.  So how to test it?   I plan to buy a
Thunderbolt but until then, anyone have any creative ideas?

I have an HP5328A with unknown calibration.  It reads 10,000,026 Hz
I have an FCC 1 kit I assembled a few years ago and it says 9,999,993 Hz.
(I can make the FCC1 read exactly 10MHz if I place it on top of the hot
FE5680, the FCC1 is very temperature sensitive.
My old Tek scope says the period is about 0.1 uS and the sine wave looks
pretty good.

BTW, 5 VDC is 76.5 mA with RS232 not connected.15 VDC is 1.5 ~ 0.8 A.
The unit does get warm.  A 3/16 x 5 x 16 inch aluminum plate worked is a
good enough heat sink.


Going to have to get a Thunderbolt.  I have an Oncore UT+ the provides a
good pulse per second but that will not help

Chris Albertson
Redondo Beach, California 



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Re: [time-nuts] A Rb with 2e-15 per day aging rate

[ws at Yahoo]

The sensitivity of that EFC input is so low on my LPRO unit, that the PS and 
DAC noises are not a problem at all.
Should add a 1K resistor in series with the Dac out before connecting it to 
anything outside of the TBolt.
Attached is an expanded 4 day plot showing part of the same LPRO run where 
the Dac is not changing at all.
Using just the Phase data, The freq offset calculates to 7e-14 and the 
ageing rate is under 1e-14


ws

***

Azelio Boriani azelio.boriani at screen.it  posted:

The frequency accuracy is measured based on the EFC variation.
I have recently received my TBolts, not yet fired up, actually preparing the
power
supply. Where is the DAC? I can't find... the LT1014 is not a DAC, the SO8
2105 is not an LT2105 nor an LTC2105. The DAC is 20bit as I can read in the
manual and for a 10-volt range (-5..+5) the resolution is 9.54uV. I think I
have to take great care in the power supply...

**
On Tue, Nov 22, 2011 at 11:00 PM, WarrenS warrensjmail-one at
yahoo.comwrote:


To TBolt nuts

A Tbolt that has been modified to use an external 10 MHz osc is all that
is needed to be able to measure freq and aging of an Rb osc to better than
1e-14 using a week long test run.
Attached is a plot showing a recent 13 day long LPRO Rb test I did.
This modified LPRO showed an unbelievable average ageing rate of only
2e-15/day over the first 12 days.
Of course anytime you get much below 1e-13 for a non Cs osc, it has some
luck evolved.
But still interesting that using ONLY a Tbolt and LadyHeather one is able
to measure freq that accurately.
(Can do even better using Dual Tbolts. Used to cancel the shorter term GPS
phase noise)

ws
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Re: [time-nuts] Sneaky Errors

[ws at Yahoo]

Simple way is to use LadyHeather.
From its output, you can tell if either or both are working correctly as 

well as how well they are working.
That is assuming of course that there is at least one working GPS satellite 
in view at all times.

If not it well tell you that also.

ws


David VanHorn D.VanHorn at elec-solutions.com

I have two thunderbolts, set up so that I can switch over to the backup unit 
if the primary fails.
All is well with that, but what could I do to detect a less obvious failure, 
like 9.99 MHz output?


If they disagree, I don't know how to resolve which is correct. 



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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

Tbolt Nuts
Something I see on Ed's SAS antenna plot that my be of interest to others.
Antenna vew looks pretty good for the most part (besides the Noth blockage) 
but there are several small 5 to 10 db nulls in the middle of otherwise 
strong signals, especially facing south.
One thing that can cause this is reflections coming from behind the antenna 
(and or multipaths)
If there is a surface behind or anything above your antenna that can 
reflect, May help a little to raise the antenna or do something to remove 
the thing doing the reflecting.


so many tricks you can do with LH
ws
**


Ed

That is a great LH plot, AND Tbolt setup.
Noise is about the same as I'm seeing.

Can also use this setup to see if the Tbolt location is set correctly by 
doing a longer plot that includes many satellites changes and see what the 
peak noise spikes are.


One little minor thing you missed that I find very useful is to set the 
DAC Plot gain (LH command GDS xxx  to 1/Dac_Gain x K (K an integer 
constant)
In your case use -269 for Dac plot gain.  Then use + or - to put the 
Dac plot exactly on top of the other two plots and that way it makes it 
very clear and very sensitive to see any drift in the Osc.
Any Osc drift will shift the offset of the Dac plot.  Using the Tbolt 
filter FD100 (or slower up to 1000)  and adding more plot gains, you can 
see Osc freq drift changes as small as 1e-12.


Thanks
ws

**
- Original Message - 
From: Ed Palmer



HI Warren,

The attached picture shows how my Tbolt reacts in TPLL mode.  I lucked
out and got about 35 minutes without a satellite switch.  The antenna
consists of a VIC-100 + about 100 feet of RG-59 + 20db amp + HP
splitter.  No choke ring or ground plane.  The antenna has good
visibility E, W, S, and up, but it's on my balcony on the South side of
a building so there's little reception from the North.  I realize that
the big hole to the North is inherent in the GPS system.

Ed




On 10/12/2011 11:46 PM, WarrenS wrote:

John wrote:

I'm curious where you got the noise data for the TBolt GPS engine

Besides the measured ADEV plot I posted at

http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gif

Attached is another way I've measured Phase noise of the Tbolt, to 
optimizing its antenna system.
This LH plot shows a total phase noise (GPS, + TBolt + Osc) of 0.087 ns 
RMS reading to reading variation at one second update, over a time 
period of 26 minutes using a one second disiplined loop.  This is the 
same as 0.87 e-10 RMS freq noise if using a 1 second time base.



On this test, I set the Tbolt's Time Constant to 1 second and its 
damping to 10.  (The Dac gain must be set right on to work right)
This causes the Tbolt's discipline loop to correct any phase error due 
to noise on the very next 1 sec update by stepping the Oscillator's 
frequency.
This Is an easy way to measure the reading to reading phase difference 
using just LadyHeather.
The data can also be interpreted.as the average RMS frequency variation 
over 1 second, which is approximately equal to the ADEV value at a tau 
of one second (1e-10).


example: If the first phase reading where zero and the next one is +1ns 
then the control loop will change the Osc freq by way of its EFC, by 
1e-9 so that the very next phase difference is  zero again. This makes 
it into a 1 sec delayed TPLL (Tight Phase Lock Loop).


I ran this same test on John's Online Tbolt. Its phase noise measured 
0.13 ns RMS.
Most of the difference was caused by satellites switching during the 
test. Each switch causes a ns or so noise spike when the number of 
satellites changed.
I also tried several other test including using just one bird with no 
switching. That was more than twice as noisy depending on which 
satellite bird I selected.


I'd like to see what the Phase noise is of other Tbolts using this same 
method, especially when using a good choke ring antenna that has a good 
sky view.


ws

*

ws at Yahoo wrote:

The noise data is my measured values which I do several different ways. 
Some

of which are:

The GPS engine value was calculated from measuring the UNFILTERED RMS 
noise
of the freq plot data using LadyHeather, backed up by the independent 
way of
looking at the  UNFILTERED 1 sec ADEV values obtained when plotting the 
ADEV

from that data using an external low noise osc.
The other proof that the data is unfiltered was done by black box 
testing of
small near instantaneous freq changes of 1e-10 and measuring and how 
long it
took the Tbolt plot to settle to the new freq value using different 
filter

setting.
The answer is that it knows the correct freq (within it's nose limits) 
in

the next 1 sec sample period when the filter is turned off.

As for the ns phase noise that is the RMS Phase noise value from LH 
using a
good LPRO osc with it's Time constant set to many hrs.  (Phase 
correction TC
was 100K

Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

I know very little about the HP58503A. Any chance it is using the old 6 
channel Oncore GPS engine?
If it is like the Oncore I tested long ago, that noise was about a decade or 
so higher than the Tbolt's phase noise.


Not sure what you can call single-shot resolution. The data is reported with 
Pico second  resolution.
The cycle to cycle max phase varation, If there is not a satellite change at 
the same time, is around  0.4ns  max error.
With the very high resolution that is output, averaging  provides a lot of 
benefit.
The noise of the Tbolt's freq (PPT) output data measured about ten times 
lower than it's phase output data at 1 sec.
How it does it is anyone guess, but looks to be some sort of high speed 
averaging going on, taken over a one second time interval.


ws

*
- Original Message - 
From: Azelio Boriani azelio.bori...@screen.it




Your work is very interesting, now I wonder what is the Tbolt
single-shot resolution? Does the Tbolt use the analog interpolator
method? I don't have the Tbolt, I have an HP58503A at work as the only
reference.


**

On 10/13/11, WarrenS warrensjmail-...@yahoo.com wrote:


John wrote:

I'm curious where you got the noise data for the TBolt GPS engine



Besides the measured ADEV plot I posted at
http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gif

Attached is another way I've measured Phase noise of the Tbolt, to
optimizing its antenna system.
This LH plot shows a total phase noise (GPS, + TBolt + Osc) of 0.087 ns 
RMS
reading to reading variation at one second update, over a time period of 
26
minutes using a one second disiplined loop.  This is the same as 0.87 
e-10

RMS freq noise if using a 1 second time base.


On this test, I set the Tbolt's Time Constant to 1 second and its damping 
to

10.  (The Dac gain must be set right on to work right)
This causes the Tbolt's discipline loop to correct any phase error due to
noise on the very next 1 sec update by stepping the Oscillator's 
frequency.
This Is an easy way to measure the reading to reading phase difference 
using

just LadyHeather.
The data can also be interpreted.as the average RMS frequency variation 
over

1 second, which is approximately equal to the ADEV value at a tau of one
second (1e-10).

example: If the first phase reading where zero and the next one is +1ns 
then
the control loop will change the Osc freq by way of its EFC, by 1e-9 so 
that

the very next phase difference is  zero again. This makes it into a 1 sec
delayed TPLL (Tight Phase Lock Loop).

I ran this same test on John's Online Tbolt. Its phase noise measured 
0.13

ns RMS.
Most of the difference was caused by satellites switching during the 
test.

Each switch causes a ns or so noise spike when the number of satellites
changed.
I also tried several other test including using just one bird with no
switching. That was more than twice as noisy depending on which satellite
bird I selected.

I'd like to see what the Phase noise is of other Tbolts using this same
method, especially when using a good choke ring antenna that has a good 
sky

view.

ws


ws at Yahoo wrote:

The noise data is my measured values which I do several different ways. 
Some

of which are:

The GPS engine value was calculated from measuring the UNFILTERED RMS 
noise
of the freq plot data using LadyHeather, backed up by the independent way 
of
looking at the  UNFILTERED 1 sec ADEV values obtained when plotting the 
ADEV

from that data using an external low noise osc.
The other proof that the data is unfiltered was done by black box testing 
of
small near instantaneous freq changes of 1e-10 and measuring and how long 
it
took the Tbolt plot to settle to the new freq value using different 
filter

setting.
The answer is that it knows the correct freq (within it's nose limits) in
the next 1 sec sample period when the filter is turned off.

As for the ns phase noise that is the RMS Phase noise value from LH using 
a
good LPRO osc with it's Time constant set to many hrs.  (Phase correction 
TC
was 100K sec). The RMS noise value is very insensitive to the filter 
setting

up to 1000 seconds because most of the phase noise is slower than 1000
seconds.

As far as the 4 to 10 ns day to day USNO data , that has nothing to do 
with
sub ns short term noise which I generally limit to more like a few 
minutes
of sampel time, and if there is a satellite change during the test run, 
then

I start the test over because I'm looking at GPS engine noise and not the
GPS noise causes by changing satellites etc.

As far as the 4 to 10 ns over a two day period, that agrees pretty well 
with

what I see some times on a bad day.
On a good day I can get more like 2 to 3 ns, with a 500 sec filter, on a 
bad

day up to 5 or 6 ns.
For some periods lasting up to 5 to 6 hrs, I've seen numbers as low as 
1.5

ns RMS.

ws

**
From: John Ackermann N8UR

In that test I was just

Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

Using the 1 sec ADEV value of  wich is limited by the one shot resolution


http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gif


The one shot resolution of the Tbolt's Phase detector is
The one shot resolutioon of the Tbolt's Freq offset data is \






***
[time-nuts] Measuring ADEV using TBolt-Tic tester
Azelio Boriani azelio.boriani at screen.it
Thu Oct 13 10:21:40 UTC 2011
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The HP58503A has the Oncore 8-channel GPS receiver. The single-shot
resolution capability is the ability to resolve the time interval
without any averaging. For example, the Fluke/Pendulum PM6681/CNT81
has a 50pS resolution, the HP5370 has 20pS, the Racal Instruments 2351
VXI TIC has 8pS single shot maximum resolution, the Wavecrest SIA3000
signal analyzer has 200femtoS hardware resolution at 3GHz.

On 10/13/11, ws at Yahoo warrensjmail-one at yahoo.com wrote:

I know very little about the HP58503A. Any chance it is using the old 6
channel Oncore GPS engine?
If it is like the Oncore I tested long ago, that noise was about a decade 
or

so higher than the Tbolt's phase noise.

Not sure what you can call single-shot resolution. The data is reported 
with

Pico second  resolution.
The cycle to cycle max phase varation, If there is not a satellite change 
at

the same time, is around  0.4ns  max error.
With the very high resolution that is output, averaging  provides a lot of
benefit.
The noise of the Tbolt's freq (PPT) output data measured about ten times
lower than it's phase output data at 1 sec.
How it does it is anyone guess, but looks to be some sort of high speed
averaging going on, taken over a one second time interval.

ws

*
- Original Message -
From: Azelio Boriani azelio.boriani at screen.it



Your work is very interesting, now I wonder what is the Tbolt
single-shot resolution? Does the Tbolt use the analog interpolator
method? I don't have the Tbolt, I have an HP58503A at work as the only
reference.

** 



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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

Using the 1 sec ADEV noise floor from the plot at
http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gifthis shows the RMS sum of the short term GPS signal's noise Plus the Tboltengine, plus the Osc, for the achievable resolution at 1 second.The one shot, 1second resolution of the Tbolt's phase data is 100 ps orlessThe one shot, 1 second 
resolution of the Tbolt's PTT detector is 10 ps orlessWhat is not too clear is how much of that is due to the Tbolt engine and howmuch is the GPS Reference.From what I've seen in my test, a large amount of that noise floor is due tothe GPS.In these cases the Tbolt's external Osc noise is low enough as not tocontribute significantly to 
the RMS sum.This is not necessary an equal comparison to your 1 shot numbers, becausethe Tbolt is using high speed averaging to get its low single shot 1second resolution by averaging over many cycles of a higher frequency.Using this basic technique and averaging over 10,000 cycles of the 100ns10MHz signal, the one shot 
resolution achieved by the TPLL2.0 is under 10femtoSecond in 1ms.ws*- Original Message -From: Azelio Boriani The HP58503A has the Oncore 8-channel GPS receiver. The single-shot resolution capability is the ability to resolve the time interval without any averaging. For example, the Fluke/Pendulum 
PM6681/CNT81 has a 50pS resolution, the HP5370 has 20pS, the Racal Instruments 2351 VXI TIC has 8pS single shot maximum resolution, the Wavecrest SIA3000 signal analyzer has 200 femtoS hardware resolution at 3GHz.** On 10/13/11, ws at Yahoo wrote: I know very little about the HP58503A. Any chance it 
is using the old 6 channel Oncore GPS engine? If it is like the Oncore I tested long ago, that noise was about a decadeor so higher than the Tbolt's phase noise. Not sure what you can call single-shot resolution. The data is reportedwith Pico second  resolution. The cycle to cycle max phase 
varation, If there is not a satellite changeat the same time, is around  0.4ns  max error. With the very high resolution that is output, averaging  provides a lotof benefit. The noise of the Tbolt's freq (PPT) output data measured about ten times lower than it's phase output data at 1 sec. How it does 
it is anyone guess, but looks to be some sort of high speed averaging going on, taken over a one second time interval. ws * - Original Message - From: Azelio Boriani Your work is very interesting, now I wonder what is the 
Tbolt single-shot resolution? Does the Tbolt use the analog interpolator method? I don't have the Tbolt, I have an HP58503A at work as the only reference.

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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

You missed something somewhere
The Tbolt's RMS noise is 100 ps for the phase and 10 ps noise on the PPT 
using unfiltered one second data.

These include the RMS sum of several noise sources.
The resolution is sub ps.
The noise is much greater than the resolution so averageing works fine

ws

Azelio Boriani azelio.boriani at screen.it

OK, so the Tbolt hardware resolution is 100pS. If you have a hardware
resolution of 100pS and do an average over the data, yes, you can obtain
greater resolution but your data has to cross the 100pS boundary to have any
variation. If your phase moves under the 100pS window your averaging can
only say that the phase has not crossed the 100pS boundary by an arbitrary
lower resolution obtained with averaging. Of course all must be stable.
Maybe the trick is to use a sampling oscillator that is not so stable so
that it can move the 100pS window to reveal if the phase is near one edge or
the other and feed the average with numbers that are not all the same. 



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Re: [time-nuts] [volt-nuts] Safe power-up. was (Solartron 7075 ...)

[ws at Yahoo]

Power factor correction power supplies has not been a BIG problem with my 
OLD recycled equipment.

I tried to Cover that case in my end note,
With switchers, turn the variact to normal and use the other safety features 
and a big enough light bulb to keep from blowing it all up if something is 
wrong.


ws

*

Poul-Henning Kamp phk at phk.freebsd.dk


In message WarrenS writes:

I don't plug ANYTHING new to me, directly into the line the first time I 
try

it.
(especially if it had a blown fuse)

Here is the solution that I use for a universal, general purpose, tester 
for

Old (and new) equipment.


That procedure is fine for linear power-supplies, but not resonably
modern switch-modes.  In particular, anything that has PFC correction
is not going to respond too well to variable voltage like that.
--
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20

***


I don't plug ANYTHING new to me, directly into the line the first time I 
try

it.
(especially if it had a blown fuse)

Here is the solution that I use for a universal, general purpose, tester 
for

Old (and new) equipment.
This is a great tool that can be used for trouble things that draw too 
much

current, has shorts, for reforming caps, Testing line voltage sensitivity
etc, etc.

First time powered up test equipment is powered from:

1) A line voltage rate light bulb in series, starting with a low wattage 
and

working  your way up.
The light bulb acts Nonlinear variable dropping resistor, which act like a
current limit and will limit the max current to a safe value but still 
have

minimum effect at lower currents due to it's Hi TC.

2) The voltage to the Light bulb comes which from adjustable variact.
The voltage rise and the Time at each voltage setting is a learned 
function

and depends on what is being tested.
If you're in a hurry, set it to the nominal line output and flip the 
switch.

The rest of the stuff will still provide protection.

3) The Variact is plugged into a KillAwatt meter
Used to constantly monitor the power, If it shows too much power is being
used, ... Well don't let it do that..

4) The Kill-a-W is plugged into a solatron 1 to 1 line regulating
transformer.
My Line regulating Solitron has the very desirable built in characteristic
that it goes into a saturation mode that limits the max output power if
overloaded
If not overloaded, it outputs a constant voltage.

5) Have a few resetable and/or  standard  fuses in there to be over safe.

The proper use of the variact's output voltage has a learning curve, 
because

equipment with switchers behave differently than things with linearly
supplies

ws

*



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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

Magnus

I probable was not very clear in my posting. (what else is new?)
There where TWO completely different subjects, goals and techniques in the
same Posting.

#1 was how to Log data for valid ADEV plots. That takes setting the filter
OFF for the reasons you state.
The ADEV tau axes provides the filter function.

Different subject altogether,  the one you copied has NOTHING to do with
ADEV plots or data.
#2 was measuring and Plotting the AVERAGE frequency (Not ADEV) and to do
that effectively, one uses LP filtered data.
For Low pass filtering, can use LadyHeather's filter function and / or the
trend line.
By looking at the freq plot at different filter settings, one can see what
type of noise is there.
And as you point out, the noise type does make a difference to the
improvement in resolution that is obtained.
I was just giving some general values that are valid for my typical type of
noise in my setup, which is mostly white over short time periods using lots
of care.
And yes can not be overstated, need to be carefull when taking and using 
data.


ws

*

On 07/10/11 19:00, WarrenS wrote:

Use the (J J) command to rezero the Phase plot (plus the cable delay if
desired)
and then read or adjust the Osc freq on the ppt plot.
With LadyHeather's filter off (F D 0) useful resolution is about 1e-10
in one second,
With the filter set to 10 sec (F D 10) useful resolution is near 1e-11
in well under one minute
With the filter set to 100 sec, resolution is around 1e-11 in a few
minutes. adding a trend line helps (G O L)


Be a little careful here. Pre-filtering will scale white-noise ADEV
linearly, please see the Power noise table I put in the ADEV wiki article:

http://en.wikipedia.org/wiki/Allan_variance#Power-law_noise

f_H is the system bandwidth and changing the pre-filtering you do change
this property. The end result is that your h_2 amount of white phase
noise is the same but only gives different ADEV values, and is not the
result of improved noise floor.

However, you can use various settings to separate between WPM and FPM
noise levels.

Cheers,
Magnus 



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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

You would first have to answer which are better to use for short term, Cs or 
Rb?

(the answer is: a good OCXO)
My guess is it does not mater, all are so much better than what is received 
by a Tbolt.
And for long term where a Cs wins, they are disiplined/corrected  in some 
way so it don't mater.


ws

*
Azelio Boriani azelio.boriani at screen.it

I know that few of the GPS constellation satellites carry a Cs clock instead
of the Rb one: is it possible to take advantage from this? I think not
because Cs and Rb satellites are equally well steered but using the masking
options of GPS receivers maybe that Cs clocks can help. 



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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

John
It would be great to have a direct Tbolt driver on TimeLab.
Right now it is so much trouble and time to use it, it takes away of the 
great real time capabilities of TimeLab.


According to Tom his really good Cs has an Flicker noise floor of almost 10 
days using 4 ns rms for phase noise.

A really good Tbolt set up will hold around 2 ns of phase noise,
so I think that means the flicker noise floor of a Tbolt will surpass Tom's 
Best Cs after 5 to 20 days.


From what I've seen it takes a few hours to a day to do better than the more 

average Cs.
I have a plot showing a Tbolt GPSDO doing better than 1e-13 (which seems 
pretty typical of most Cs) over a day using a compensated LPRO.


ws
**
John Miles jmiles at pop.net


Very Important note, The above is NOT available directly from
LadyHeather's
ADEV plots  (at least not yet - Mark is a revision coming?),
What one needs to do is to log the Tbolt's Freq and Phase data at the 1sec
rate and then use that data with an external ADEV program such as Ulrich's
Plotter or John's TimeLab.
Note for TimeLab users. LH adds some extra comment data lines in it's log
file that need to be manually removed before using the data file with some
versions of TimeLab.


I had a 'native' Thunderbolt driver in the old TI.EXE program that I could
probably bring across to TimeLab without much trouble.  It didn't work with
the COM port directly, but with a Heather TCP/IP server.  That means that
it takes some extra work to set up since you have to run two programs, but
it also means that you can run LH and TimeLab on the same Thunderbolt at the
same time, with no need to monkey around with logfiles.

I'll have a look at it to see if I can bring that code back from cold 
storage.



. . .
If you want even more accuracy, watch the PHASE change over a few days.
This  can check your best Primary Cs standard's frequency.


Eventually a GPS clock will reach something like a flicker floor where the
ADEV trace flattens out and stops decreasing over time.  I don't really know
where the flicker floor is on a Thunderbolt-class clock versus where it will
be on a local cesium standard.  The sigma-tau statistics for the more common
HP 5061-era clocks were never really specified for periods more than a day,
while at the same time, there don't seem to have been many long-term tests
run on Thunderbolts and other GPS clocks to see where their performance
flattens out.  It would be good to see some more long-term trials.

Said, do you have data for the long-term (multi-week) floors of the various
Jackson Labs GPSDOs?

Intuitively, I don't believe a GPSDO can outperform an HP 5071A-era clock
over periods greater than a few hours.  But it may be reasonable to
benchmark 5061A-class standards with a good GPSDO setup.   We really need
some more data from trials lasting multiple weeks.

-- john 



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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

John
What was the RMS and PP phase noise for your 8e-14 test?

Something to keep in mind is that although the Z3801 has a better Osc than 
the typical Tbolt.
Long term, really low noise is all about the quality of the GPS signal and 
engine.


The Z3801's GPS engine is far inferior and not even close to the 10 to 100 
ps, 1 sec noise that a Tbolt engine has.
So how much does that effect the mid term GPS Phase noise which is highly 
dominated by how good of antenna system one has.

Sounds like comparison is needed.

ws
*

Some test like these are on my list for this winter.  I am planning to look 
at a Z3801A versus a couple of 5061 class units: one with a high stability 
tube that I think is in very good condition, and another with an FTS 
replacement tube of probably typical surplus quality.  I can also add a 
TBolt into the mix.  I'm hoping to lash up multiple 5334 counters in TIC 
mode so I can do several comparisons simultaneously.


In an early test of the 004 tube vs. Z3801A over a week or so, I saw what 
looked like a floor in the 8e14 range.


John 



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Re: [time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

The noise data is my measured values which I do several different ways. Some 
of which are:


The GPS engine value was calculated from measuring the UNFILTERED RMS noise 
of the freq plot data using LadyHeather, backed up by the independent way of 
looking at the  UNFILTERED 1 sec ADEV values obtained when plotting the ADEV 
from that data using an external low noise osc.
The other proof that the data is unfiltered was done by black box testing of 
small near instantaneous freq changes of 1e-10 and measuring and how long it 
took the Tbolt plot to settle to the new freq value using different filter 
setting.
The answer is that it knows the correct freq (within it's nose limits) in 
the next 1 sec sample period when the filter is turned off.


As for the ns phase noise that is the RMS Phase noise value from LH using a 
good LPRO osc with it's Time constant set to many hrs.  (Phase correction TC 
was 100K sec). The RMS noise value is very insensitive to the filter setting 
up to 1000 seconds because most of the phase noise is slower than 1000 
seconds.


As far as the 4 to 10 ns day to day USNO data , that has nothing to do with 
sub ns short term noise which I generally limit to more like a few minutes 
of sampel time, and if there is a satellite change during the test run, then 
I start the test over because I'm looking at GPS engine noise and not the 
GPS noise causes by changing satellites etc.


As far as the 4 to 10 ns over a two day period, that agrees pretty well with 
what I see some times on a bad day.
On a good day I can get more like 2 to 3 ns, with a 500 sec filter, on a bad 
day up to 5 or 6 ns.
For some periods lasting up to 5 to 6 hrs, I've seen numbers as low as 1.5 
ns RMS.


ws

**

)
r

- Original Message - 
From: John Ackermann N8UR


In that test I was just capturing the ADEV table from the TSC-5120 so don't 
have raw phase data.


I'm curious where you got the noise data for the TBolt gps engine -- that's 
far better than I've seen quoted before.  The Trimble data sheet that I 
found specs the system PPS accuracy at 20 nanoseconds one sigma; they don't 
separately spec the GPS engine.  (The data sheet for the current Thunderbolt 
E data sheet says 15 nanoseconds.)


The USNO says that their filtered, linear fit time transfer measurements 
over a two day period, over the entire constellation, have an RMS residual 
of 4 to 10 nanoseconds without SA (http://tycho.usno.navy.mil/gpstt.html). 
That may not be apples-to-apples methodology, but it implies that 
sub-nanosecond results may be difficult to obtain.


John

On Oct 7, 2011, at 4:16 PM, ws at Yahoo warrensjmail-...@yahoo.com 
wrote:



John
What was the RMS and PP phase noise for your 8e-14 test?

Something to keep in mind is that although the Z3801 has a better Osc than 
the typical Tbolt.
Long term, really low noise is all about the quality of the GPS signal and 
engine.


The Z3801's GPS engine is far inferior and not even close to the 10 to 100 
ps, 1 sec noise that a Tbolt engine has.
So how much does that effect the mid term GPS Phase noise which is highly 
dominated by how good of antenna system one has.

Sounds like comparison is needed.

ws
*

Some test like these are on my list for this winter.  I am planning to 
look at a Z3801A versus a couple of 5061 class units: one with a high 
stability tube that I think is in very good condition, and another with an 
FTS replacement tube of probably typical surplus quality.  I can also add 
a TBolt into the mix.  I'm hoping to lash up multiple 5334 counters in TIC 
mode so I can do several comparisons simultaneously.


In an early test of the 004 tube vs. Z3801A over a week or so, I saw what 
looked like a floor in the 8e14 range.


John

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Re: [time-nuts] Rubidium (Rb) or Caesium (Cs)

[ws at Yahoo]

Doug wrote:

If you are constantly jerking the control voltage back-and-forth ...


Interesting, I can certainly see how that could be the case if one tried to 
Track a GPS too fast,

Or used a noisy non Tbolt engine, Or a poor control loop.
But it is not in any way consistent with what I see happening.
Maybe it has something to do with the fact that my constant Jerking is 
only 2 e-15 per Dac step, which is far below any noise level,

and the daily change is under 1e-12 PP with a several hr time constant.
I wonder if that fits within their definition of only making small changes 
every 24 hrs?


ws

***
Warren,

I used to work at Efratom.  The rubidium engineers used to say that the LPRO
did not work well with constant frequency corrections such as with GPS.
They claimed that very slight corrections should only be made once every 24
hours.  And then, it may take up to a week or longer to pull the frequency
to the desired amount.  If you are constantly jerking the control voltage
back-and-forth, the LPRO will get to where it develops jitters!
Regards, Doug, K4CLE

*

-Original message-
From: WarrenS warrensjmail-one at yahoo.com
To: Discussion of precise time and frequency measurement
time-nuts at febo.com
Sent: Mon, Oct 3, 2011 16:59:19 GMT+00:00
Subject: [time-nuts] Rubidium (Rb) or Caesium (Cs)

Rubidium (Rb) or Caesium (Cs) standard reference oscillator?

What will give the more accurate absolute Frequency source over day to day
averages?
A primary Cs (the types available to time nuts) or a optimally disciplined
GPS Rb Osc?

By definition Cs is the primary time standard,
but there are several things that effect a time-nut's Primary Cs
Standard's absolute frequency including how it is built and maintained, if
it has the high stability option and Einstein.
What I'd like to find out is how accurate a GPS Disciplined_Rb_Osc can be
made compared to the typical Cs out there.

I'm experimenting to find out how accurate a freq standard can be made using
a LPRO Rb disciplined to a Tbolt.
Using a  temperature compensated and tweaked LPRO Rubidium (Rb) oscillator,
I'm getting low e-13 per deg F and day to day freq variations (compared to
GPS) even before being disciplined.
When the LPRO Rb is disciplined to GPS using a well setup Tbolt with an
extended time constant of a few hours,
their phase difference stays with-in a couple of ns RMS, and of course the
difference between them long term is zero.
What I would like to determine is how accurate that really is.

ws

** 



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Re: [time-nuts] Rubidium (Rb) or Caesium (Cs)

[ws at Yahoo]

Magnus

One problem is that I do not have anything that is known better or even near 
as good as the GPS to compare against when it comes to accuracy or stability 
at greater than one day.
(If I did I'd be working on making it better instead of improving a cheap 
LPRO Rb)


As you point out, a HP5061A Cs does not start becoming more stable than a 
good Rb until after about a day, which by then the GPS is dominate in a good 
GPSDO.
So my basic question:  Is the HP Cs is more stable than a good GPSDO setup 
at times greater than a day.


The Top hat test is a good Idea that I'll try and set something up,
but a couple of problems with it is that the 3 or 4 units under test should 
at least be close in noise and one needs more than one Cs to be sure of the 
results.


ws




Dear Warren,

On 03/10/11 18:58, WarrenS wrote:

Rubidium (Rb) or Caesium (Cs) standard reference oscillator?

What will give the more accurate absolute Frequency source over day to 
day averages?
A primary Cs (the types available to time nuts) or a optimally 
disciplined GPS Rb Osc?


By definition Cs is the primary time standard,
but there are several things that effect a time-nut's Primary Cs 
Standard's absolute frequency including how it is built and maintained, 
if it has the high stability option and Einstein.
What I'd like to find out is how accurate a GPS Disciplined_Rb_Osc can be 
made compared to the typical Cs out there.


If you want absolute frequency then a GPSDO rules over any Cs a normal 
time-nut can get.


Looking only for stability, then a HP5065A will be more stable than a 
HP5061A up to about 100 ks where the HP5061A becomes more stable according 
to the ADEV charts that I have found after a quick look on the net (using 
HP5065A ADEV and HP5061A ADEV as search terms).


I'm experimenting to find out how accurate a freq standard can be made 
using a LPRO Rb disciplined to a Tbolt.
Using a  temperature compensated and tweaked LPRO Rubidium (Rb) 
oscillator,
I'm getting low e-13 per deg F and day to day freq variations (compared 
to GPS) even before being disciplined.
When the LPRO Rb is disciplined to GPS using a well setup Tbolt with an 
extended time constant of a few hours,
their phase difference stays with-in a couple of ns RMS, and of course 
the difference between them long term is zero.

What I would like to determine is how accurate that really is.


Best way is to measure against a cesium or free-running rubidiums. 
Three-cornered hat will help.


Cheers,
Magnus



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Re: [time-nuts] HP 10811 Response I Replies

[ws at Yahoo]

A problem I've seen when using the hermetic sealed soldered version of the 
10811 from a dual oven unit,
 is when the case is sealed the osc makes a good barometer because of changes 
in its case due to barometric changes.
A 1 inch difference (such as 30 to 29) caused something on the order of 1e-11 
freg change.
To see the effect just need to put a little pressure on  the case 
So now I'm trying to determine which is worse, leaving the freq adj screw tight 
and sealed or leaking a little, inside a box containing desiccant.

ws

**
 
 Heating up a space does not change the absolute humidity AFAIK.
 It only changes the relative humidity.  We did tests where we
 sealed a 10811 inside a box that was held together with so-called
 hermetic epoxy.  We put it in an environmental chamber at a
 constant temperature and constant low humidity and let it stabilize.
 We then increased the humidity to something like 80%,
 while holding the temperature constant.  Within
 minutes the frequency changed more than the spec for the entire
 temperature range.  Therefore, you should do your experiment with
 the hermetic version of the 10811.  The hermetic version is soldered
 shut, rather than using epoxy, which turns out not to be hermetic,
 no matter what they claim.
 
 Rick Karlquist
 
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Re: [time-nuts] HP 10811 Response I Replies

[ws at Yahoo]

Within minutes the frequency changed more than the spec


For humidity to get thru something like that it takes weeks or more it does 
it at all.
That fast of reaction, Sure sounds like some other effect like blowing a 
little air on the case or loading the osc output with water in the output 
cable etc, etc.
I think it is safe to say the effect was not due to water inside, unless 
there was a hole.


ws

*
Chuck Harris cfharris at erols.com

You had a leak.  If epoxy was really as bad as you indicate,
it would not be usable for holding pressure, or mild vacuum,
and yet it is.  Somehow, someway you left a big hole in the
bucket.

-Chuck Harris


Rick Karlquist wrote:

Perry Sandeen wrote:


Wrote: Doing what you describe will result in a very sensitive humidity
sensor, having eliminated the thermometer effect.

I do not understand.  I believed that since the OCXO temperature will be
substationally higher than the surrounding temps, any residual moisture
would migrate to a lower temperature.  The fiberglass insulation inside


Heating up a space does not change the absolute humidity AFAIK.
It only changes the relative humidity.  We did tests where we
sealed a 10811 inside a box that was held together with so-called
hermetic epoxy.  We put it in an environmental chamber at a
constant temperature and constant low humidity and let it stabilize.
We then increased the humidity to something like 80%,
while holding the temperature constant.  Within
minutes the frequency changed more than the spec for the entire
temperature range.  Therefore, you should do your experiment with
the hermetic version of the 10811.  The hermetic version is soldered
shut, rather than using epoxy, which turns out not to be hermetic,
no matter what they claim.

Rick Karlquist





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Re: [time-nuts] Making a HP 10811 and similar types better in the

[ws at Yahoo]

  As already stated, there are many different ways to design and or tune  a 
temperature controller so it does not overshoot.
The trade off being that it may then take a little longer to get to the 
finial temperature.
BUT SO WHAT???  If one is concerned about a little oven overshoot then they 
are missing the much  BIGGER picture.
Why was the oven off in the first place? That will cause such a bigger 
problem, No one is going notice a little overshoot.

The Osc needs to be kept powered up with the oven on.

If the primary temperature sensing thermistor is on top of the heater,
you have already compromised the oven design because the xtral is not going 
to be at that exact same temperature.
If you need to go that far to stabilize a hard to control loop, then better 
to add a second thermistor.
(Not a dual oven, Just One heater, with two temperature sensors, where the 
outer thermistor ia outside the error loop but acts as a feed forward to the 
PID loop)



Concerning the 11 steps outlined on how to make a HP10811 better
Several of them are unnecessary and way overkill,  or there are simpler ways 
to get even better results, and some I find even undesirable.
Just one example, don't always need some super low noise voltage reference 
to drive the EFC.
Just need to reduce the range to no more than necessary because the best 
voltage reference you can use is ground.

Example:
If you're going to use a  GOOD pot to set the EFC voltage them best to limit 
the pot's tuning range to about 1000 times the desired resolution.
1e-12 resolution  x 1e3  = 1e-9 total Pot tuning range, which means the Pot 
voltage should be divided down by about 1000 before it is connected to the 
EFC.


ws

***
Hi

If the thermistor is on top of the heater, the heat will cut back before 
anything inside the oven overshoots on warmup.


Bob
*

On Sep 21, 2011, at 7:02 PM, J. Forster wrote:


That is not always as easy as it sounds.

The thermal equivalent of a rigid body does not exist. If you apply heat
to a block of metal at one end, it takes a while for it to propagate to
the other end. In fact, a long thin rod looks a lot more like a
transmission line than an isothermal block.

This matters because if you try and increase the loop gain, the wrap-up of
the phase shift soon reaches 180 degrees, and the thing becomes unstable
as negative FB at low frequencies becomes positive FB at higher
frequencies.

-John

===



Hi

Actually, overshoot is pretty easy to eliminate on a conventional OCXO by
picking a good location for the thermistor. The heater will always run
hot, but the rest of the stuff does not have to.

Bob


On Sep 21, 2011, at 6:37 PM, Magnus Danielson wrote:


On 09/22/2011 12:30 AM, Chuck Harris wrote:

Perry Sandeen wrote:

GM List,
..The

ovens are proportionally controlled. On start-up all ovens,
proportional or not,
will have over-shoot. Some more, some less. An inescapable fact of
life.


Imagine that the set point is variable, and can be set below the
desired
temperature. Then imagine that the set point can approach the desired
temperature more closely as it gets closer to the desired temperature.

... And you will have discovered (100 years late) the PID controller.

PID controllers do not have to overshoot the desired temperature. It is
not an inescapable fact of life. 30 years ago I was designing PID
controllers,
with a little microprocessor magic, that could quickly arrive at the
set
point
temperature and never, I repeat, never, exceed that temperature.
Someone's
internal organs would have become toast if it did.


Overshot is fairly easy to avoid for a well controlled PID loop simply
by setting the damping factor properly.

PIDs is nice in that you can control loop bandwidth and damping factor
fairly well. Overshot properties vs. damping factor is a well researched
field and already tabulated before I was born.

Cheers,
Magnus





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Re: [time-nuts] Making a HP 10811 and similar types better in the

[ws at Yahoo]

I hope it is not being suggesting that is an optimal PI  (no D) oven 
controller for limiting overshoot.

Many other ways to do it with less overshoot IF that was needed or wanted.

From the test I've done on it, Less overshoot is not necessary and likely 

not desired.
It overshoots a little but does not ring which is near the optimal tuning 
for a simple basic PI controller.
And of course today there is always the choice to rise the resistor values 
and use a  better amp which has the same effect as rising the cap's value.



ws




Rick Karlquist richard at karlquist.com wrote:



ws at Yahoo wrote:
 As already stated, there are many different ways to design
and or tune a temperature controller so it does not overshoot.



The 10811 control loop is constrained by the large oven mass
and the limited size of the integrator capacitor.  The
capacitor is barely large enough in capacitance to prevent
loop oscillation but on the other hand is barely small
enough to physically fit in the available space.  Unfortunately, no
advances in capacitor size have occurred in the last 30
years, so we are still stuck with the original design.
BTW, you cannot use a metallized mylar capacitor in an
integrator, you must use a foil and mylar type.  This is
due to the healing process that metallized mylar
capacitors undergo.


Rick Karlquist 



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[time-nuts] ways to make a HP 10811 better

[ws at Yahoo]

This is mentioned ( that the 10811 is not always operated at it's exact 
turn over temperature) in the HPJ article on the 10811.

(Required reading for anyone playing with 10811's).
Rick Karlquist N6RK

**
Yes it does and it also says that is to save testing time and make it field 
repairable etc.
Problem is that now the resulting freq sensitivity can be as high as 1.5e-8 
/deg (at the xtral)

This is Many decades greater than what it is at the true turn over point.
Since I try and remove any measurable freq change,
and 1e-12 freq change is easy enough  to measure (in = 0.1 sec),
Call me nuts, but seems worth while to spend a few extra minutes of  nut 
time to find and set the turn over temp to be exact on so that any small 
oven drift no longer effects the freq.



One big different is they need to make all of them meet a min spec,
and I just want to find one best one that is decades better than their worse 
case specs.


Next experiment needed is to see if anything can be made better by changing 
the power split between the two heater transistor.
Interesting enough, they made the point it was never re-tested after they 
got out of protype.


BTW
I changed the subject title so as not to add more noise to the latter OT gas 
and speed postings.
For me, don't need the gas and OIL or even a basement full of metal and 
mercury, A simple outer oven works so much better.


ws


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Re: [time-nuts] Oscillator Buddy

[ws at Yahoo]

Brooke

One simple way I'veused to eliminate the two problems you brought up is by 
Greatly restricting the tuning effect of the Dac voltage.
Only big downside is you then may have to manually reset the nominal Osc 
freq every once in a while if the Dac gets near a limit.
With a little thought an 8 bit Dac is more than enough to make a great GPSDO 
out of a good Osc,
as long as the Osc also has a course freq tuning method like the HP 10811 
does.


But what I was suggesting is not a GPSDO, but an open loop freq compensator.
Simplified example:
Make the analog output of the PIC equal to (K1 times measured temperature) + 
(K2 times lapsed time)
With that, K1 can be used to cancel the Osc tempCoef and K2 the daily ageing 
rate.


Having fun,  always
thanks
ws

**

Hi Warren:

I looked into using a PIC to make a GPSO and there are two problems:
(1) is the number of bits you can get in the D/A converter.  The best
solution I've seen is used in the Quantic Q5200 GPS receiver which has
what amounts to an internal GPSDO with 48 bits in the oscillator drive.
It's in their US Patent 5440313 (link on Q5200 web page).
http://www.prc68.com/I/Q5200.shtml

(2) Noise on the control voltage.
When I was at HP/Agilent a neighboring engineer was THE man on their
4352 VCO/PLL tester.  The D/A converter in it and in the combo boxes
(4395  4396 among others) not only had a lot of bits it was also
extremely quiet.  Getting both of these is far from simple.
http://www.prc68.com/I/4395A.shtml

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.End2PartyGovernment.com/


WarrenS wrote:
What may make a nice little nut-project is a simple PIC processor type 
Oscillator Buddy circuit that would reduce the effects of environmental 
and time caused oscillator frequency drift errors using the oscillator's 
EFC analog input.


What makes a nice Time-Nut Oscillator candidate for this project is one 
that is repeatable AND predicable.
I am continually ageing and testing several  good oscillators including 
single and dual oven HP10811s and LPRO Rb to find the most predicable 
repeatable ones.


On these type of selected Oscillators, after minimizing the frequency 
uncertainty errors due to basic things like power supply effects and RF 
load changes and keeping them in a reasonable stable environment, the main 
errors I see are:


1) ADEV noise at tau = 1sec for OXCOs and at 100 sec for RBs  (typical 
range is from 0.2e-12 to 2e-12)


2) Temperature coefficient   (the typical range is from +- 1e-13 to 1e-10 
per degC)


3) Ageing rate  (typical range is + - 1e-13 to 1e-10 per day)

4) Barometric pressure (Typical effect  TBD)

I have found it is  possible to reduce the environment and time caused 
freq drift errors by 10 to 1 or more on some of the better selected 
oscillators using open loop correction techniques.


Disciplining the Osc with GPS in a closed loop (aka Tbolt GPSDO) is the 
typical and most effective way to reduce the effects of #2, 3,  4 above, 
but that does have some limitations and the better the disciplined osc is 
open loop then the better the closed loop results.


Any thoughts and comments on an Oscillator Buddy project.

ws
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Re: [time-nuts] Averaging effects

[ws at Yahoo]

Others said:
There is a downside to this approach which should be understood, it will 
also averaging out the white noise of the DUTs.
The time interval counter method severely undersamples the phase noise 
spectrum leading to aliasing effects.

The measured ADEV depends on the associated filter bandwidth
Filtering is tricky since you will both reduce the measurement systems 
noise as well as the the DUTs noise.

The aliasing effect is definitively there.
Question is how to remove the system noise from the DUT noise


One way to avoid those trade-offs is to do the frequency difference 
averaging with a TPLL (Tight Phase Lock Loop) using a proper integration 
of it's output over the tau time period.

example at: http://www.thegleam.com/ke5fx/tpll.htm

ws

**
Magnus Danielson magnus at rubidium.dyndns.org

Hej Bruce,

On 12/27/2010 08:13 PM, Bruce Griffiths wrote:

Tom Van Baak wrote:

There is a downside to this approach which should be understood, it
will also averaging out the white noise of the DUTs.


Correct. A similar white noise effect can happen if you average
the raw data itself. See the plot at the bottom of:
http://www.leapsecond.com/pages/adev-avg/


Its a little more complicated than that.
The measured ADEV depends on the associated filter bandwidth (typically
for 1Hz sampling one uses a low pass (for the phase fluctuations) filter
bandwidth of 0.5Hz or less).
When one uses a time interval counter the counter input system noise
bandwidth may be as high as 100MHz (5370A/B) or 500MHz or more (DTS2070)
whereas the crystal oscillator buffer amp (principal source of OCXO
white phase noise floor) may have a somewhat lower bandwidth. The time
interval counter method severely undersamples the phase noise spectrum
leading to aliasing effects.
Averaging of this type creates a low pass filter that will reduce the
system noise to a large extent whilst not greatly affecting the
measurement as the equivalent filter bandwidth will still be much larger
than 0.5Hz and the equivalent filter response is far from ideal.


True, but it is tricky since you will both reduce the measurement
systems noise as well as the the DUTs noise (which is what you intend to
measure).

The aliasing effect is definitively there.

Question is how to remove the system noise from the DUT noise, and I
know of only approach which really avoids it is cross-correlation, but
otherwise it is only various measures to remove and filter out the
signal from noise before it is folded in, i.e. conservative design measure.

Anyway, I wanted to play around with averaging to see how the filtering
effect behaves.

Cheers,
Magnus 



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Re: [time-nuts] Help with KE5FX Thunderbolt

[ws at Yahoo]

Try again, I reset it. The setting were so far off, that may of caused your 
problems.

ws



time-nuts] Help with KE5FX ThunderboltGeraldo Lino de Campos geraldo at 
decampos.net

Sat Nov 27 20:42:34 UTC 2010
When running KE5FX thunderbolt, it doesn´t take the station coordinates
stored in the tunderbolt, and uses Lat:45.414 N, ... , probably a
program default.

If  I try to enter the coordinates manually (commands s L), the program
crashes when entering the first digit after the decimal point (my coordinate
is negative).

The traditional Lady Heather works correctly, and take the coordinates
stored in the tunderbolt.

Any suggestion?


Geraldo
geraldo at decampos.net 



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Re: [time-nuts] Do I have a defective thunderbolt?

[ws at Yahoo]

geraldo
Is this normal, or do I have a defective unit?


It is normal for a defaul Tbolt, with any (or all)  of the following:

MultiPath
a poor antenna, 
a poor sky view, 
a poor location survey
a poor elevation mask setting
a poor Sat Level setting
a poor TC setting
A poor Sat cable

ALL need to to be corrected to make it lots better.
Lady Heather has all the tools to find which ones are effecting you, But I 
could not see your plots.
If you want more information, post a LH log file and how/where I can view your 
plots.

Have fun
ws

ps damping should remain at about 1.0

***
[time-nuts] Do I have a defective thunderbolt?
Geraldo Lino de Campos geraldo at decampos.net 
Wed Nov 17 16:21:20 UTC 2010 


I have a thunderbolt acquired from TAPR. Almost every time the number of
satellites change, there is an abrupt change in the DAC voltage - as high as
1 mv, sometimes. See
www.decampos.net\LH\LH1http://www.decampos.net/LH/LH1.png
- a graph with time constant 200 and Damping 4. Using much higher values
improve the situation, as can be seen in
www.decampos.net\LH\LH2.pnghttp://www.decampos.net/LH/LH2.png, time
constant 1000 and damping 100 (note the change in the DAC scale), but
the jumps are still present.

Is this normal, or I have a defective unit?

The antenna is located in a window, with several buildings nearby, so the
change in the number of satellites is frequent.
-- 

geraldo at decampos.net
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Re: [time-nuts] What is the correct Allan value?

[ws at Yahoo]

It is easer for me to scale the nom freq setting than the data so
I scaled the 1E+7 osc freq by 1e+4, because my raw data is in parts per 
1e-11 instead of in Hz.
Gives the same answer either way. I'm using an improved TPLL to take the raw 
data,  Ulrich's great Plotter program to do the plots.


ws
***

SAIDJACK at aol.com SAIDJACK at aol.com
Hi there,

how can the nominal frequency be 1E+11 Hertz (in other words 0.1 
TeraHertz)??


For the 10811A it should be set to 1E+7.

Also, what instrument are you using that gives you xE-13 resolution on
33ms sample rate (30 samples per second at 0.5 parts per trillion 
resolution)?


bye,
Said 



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