[time-nuts] Fwd: Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

2017-06-06 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html

I said that thermistors have been obsolete for 40 years not
themocouples. (With a FEW rare exceptions)  I do not consider platinum
wire to be a thermistor.  I own a 100 Ω platinum wire thermometer for
the DVM in my 2236 Tekronix.  It is not worth much without a Kelvin
connection.  From 0° C to to 100° C it changes 40 Ω and uses banana
plugs.  Those are unstable by ~ 0.2Ω.  This is 0.5° C of error and
intermittent.  It is worthless for designing ovens.

I use thermocouples in my Fluke 52 stereo thermometers all the time.
They will work at nearly red heat and are stable.  They are hard to
use because they only produce 40 μV/C° and require a cold junction
comparison.  The cold junction is easily calibrated by an ice bath
however.  Thermistors depend on the cauldron in which they were
stirred by the witches at manufacture.

In the range of -55° C to 150° C, I don't think anything can match the
AD590 or equivalent for repeatability, accuracy, stability, linearity
or convenience.  They are not affected by lead resistance and can use
tiny wires. It will tolerate 3,000 Ω of lead resistance and can be
multiplexed. The chip itself is 52 mils by 42 mils or comparable to a
thermocouple bead.  I figured out that two of them can be driven back
to back by a square wave and two temperatures monitored at once with
the same pair of wires.  An Analog Devices product engineer split a
$100 prize with me for my invention.

πθ°μΩω±√·Γλ
WB0KV

-- Forwarded message --
From: Attila Kinali 
Date: Sun, Jun 4, 2017 at 4:59 PM
Subject: [time-nuts] Temperature sensors and quartz crystals (was:
HP5061B Versus HP5071 Cesium Line Frequencies)
To: Discussion of precise time and frequency measurement 

Moin,

This discussion is kind of getting heated.
Let's put some facts in, to steer it away from
opinion based discussion.

On Sun, 4 Jun 2017 08:44:33 -0700
"Donald E. Pauly"  wrote:

> I stand by my remark that thermistors have been obsolete for over 40
> years.  The only exception that I know of is cesium beam tubes that
> must withstand a 350° C bakeout.  Thermistors are unstable and
> manufactured with a witches brew straight out of MacBeth.  Their
> output voltages are tiny and are they inconvenient to use at different
> temperatures.

If you really mean thermistors, and not, as Bob suggested thermocouples,
then I have to disagree. The most stable temperature sensors are
platinum wire sensors. The standards class PRT's are the gold standard
when it comes to temperature measurement, for a quite wide range
(-260°C to +960°C) and are considered very stable. They offer (absolute)
accuracies in the order of 10mK in the temperature range below 400°C.
Even industrial grade PRT sensors give you an absolute accuracy better
than 0.1K up to 200-300°C. The "cheap" PT100 are more of the order of 1-10°C
accuracy... all numbers just using a two-point calibration.

For more information on this see [1] chapter 6 and [2] for industrial sensors.

NTC sensors have a higher variablity of their parameters in production
and are usually specified in % of temperature relative to their reference
point, which is usually 25°C. Typical values are 0.1% to 5%. Additionally
there is a deviation from the reference point, specified in °C, which
is usually in the order of 0.1°C to 1°C.

The NTC sensors are less accurate than PT sensors, but offer the advantage
of higher resistance (thus lower self-heating), higher slope (thus better
precision). Biggest disadvantage is their non-linear curve. Their price
is also a fraction of PT sensors and due to that you can have them in
many different forms, from the 0201 SMD resistor, to a large stainless
steal pipe that goes into a chemical tank. NTCs are the workhorse in
todays temperature measurement and control designs.

The next category are band-gap sensors like the AD590. Their biggest
advantage is that their 0 point is fix at 0K (and very accurately so).
Ie they can be used with single point calibration and achieve 1°C accuracy
this way. Their biggest drawback their large thermal mass and large
insulating case, because they are basically an standard, analog IC.
Ie their main use is in devices where there is a lot of convection and
slow temperature change. Due to their simple and and quite linear
characteristics, they are often used in purely analog temperature
control circuits, or where a linearization is not feasible.
But only if price isn't an issue (they cost 10-1000 times as
much as an PTC). Their biggest disadvantage, beside their slow
thermal raction time, is their large noise uncorrelated to the
supply voltage, and thus cannot be compensated by ratiometric measurement.
They are also more suceptible to mechanical stress than NTC's and PT's,
due to their construction. Similar to voltage references (which they
actually are), their aging is quite substantial and cannot be neglect

[time-nuts] TAPR GPS Experimenters Kit

2017-06-04 Thread Donald E. Pauly
We are finishing a pair of HP5061B cesium standards which we have up
and running.  We would like to acquire a GPS disciplined oscillator
with 5 or 10 mc output for comparison with the cesium clocks.  1 pulse
per second would be nice but is not mandatory.  A roof antenna with
preamp that could drive 100 feet or so of foam RG-58 is required.
Does anyone have such a device that needs a new home?  If not, what
should we look for on eBay?

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Dave Mallery 
Date: Sun, Jun 4, 2017 at 8:54 AM
Subject: Re: [time-nuts] TAPR GPS Experimenters Kit
To: Discussion of precise time and frequency measurement 


hi

I have been having great results with my M12 and Lady H.  I (foolish me)
had tried to cobble up a Perl program at first...  just browse through some
of the 400+ pages of heathgps.cpp to see why that was a bad idea!  Both my
M12 and my Tbolt are controlled by Heather running on two PI3s.

Now, i would like to get a Lucent RFTG-u REV-0 to run using the PPS from
the M12.  there is a nice PPS interrupt driven arduino sketch on the Sync
Channel Blog.  I'd love to hear from anyone who is also trying this.

73

dave mallery, k5en


On Sun, Jun 4, 2017 at 7:03 AM, Gregory Beat  wrote:

> Mark -
> Yes, it does. :-)
> The "S" and "!" menus are the most frequent menus I use with LH.
>
> Jerry is using SynTAC.
> After a few e-mail exchanges, off-list, problem was antenna location.
>
> gb
> ===
> So does Lady Heather... the "S" menu control things like self-surveys,
> entering fixed position coordinates,  and the receiver operating mode.  SN
> will put it in Navigation (3D) mode.  SH will put it in position Hold mode
> (timing mode).
>
> Sent from iPad Air
> ___
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> mailman/listinfo/time-nuts
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>



--
Dave Mallery, K5EN (ubuntu linux 16-10)
PO Box 15  Ophir,  OR  97464

  linux counter #64628 (since 1997)
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-04 Thread Donald E. Pauly
I own several Fluke 52 stereo thermometers with K themocouples.  They
run 40 μV/C°.  All thermistors have tiny outputs without op amps.
They also suffer from self heating.  AD590 sensors give AT LEAST 15
mV/C° without op amps.  If a regulated 3,000V supply is available they
can give 2 V/C° into a 1 Watt 10 Meg resistor.

πθ°μΩω±√·Γλ
WB0KVV


-- Forwarded message --
From: Bob kb8tq 
Date: Sun, Jun 4, 2017 at 11:46 AM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement 
Cc: "rwa...@aol.com" , "Donald E. Pauly"



Hi

I think you have thermistors and thermocouples a bit mixed up. You can get
quite substantial output voltages from a thermistor bridge….

Bob

> On Jun 4, 2017, at 11:44 AM, Donald E. Pauly  wrote:
>
> I stand by my remark that thermistors have been obsolete for over 40
> years.  The only exception that I know of is cesium beam tubes that
> must withstand a 350° C bakeout.  Thermistors are unstable and
> manufactured with a witches brew straight out of MacBeth.  Their
> output voltages are tiny and are they inconvenient to use at different
> temperatures.
>
> Where did you get the idea to use a 1 k load for an AD590?  If you run
> it from a -5 V supply you can use a 15 k load to a +5V supply.  This
> gives 15 V/C° output.  If you drive it from a 10 Meg impedance current
> source, you get 30,000 V/ C°.  If I remember correctly, I drove a
> power MOSFET heater gate directly in my prototype oven 20 years ago.
> It would go from full off to full on in 1/15 ° C.  Noise is 1/25,000 °
> C in a 1 cycle bandwidth.
>
> The room temperature coefficient of an AT crystal is -100 ppb per
> reference cut angle in minutes.  (-600 ppb/C° for standard crystal)
> The practical limit in a crystal designed for room temperature is
> about 0.1' cut accuracy or ±10 ppb/C°.  If you have access to an
> atomic standard, you can use feed forward to get ±1 ppb/C°.  If the
> temperature can be held to ±0.001° C, this is ±1 part per trillion.
> This kind of accuracy has never been heard of.  Feed forward also
> allows you to incorporate the components of the oscillator into the
> thermal behavior.  It does no good to have a perfect crystal if the
> oscillator components drift.
>
> πθ°μΩω±√·Γλ
> WB0KVV
>
> -- Forwarded message --
> From: jimlux 
> Date: Sun, Jun 4, 2017 at 4:47 AM
> Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
> To: time-nuts@febo.com
>
>
> On 6/3/17 9:56 PM, Donald E. Pauly wrote:
>
>> It was only in the early 70s that Analog Devices invented the AD590
>> solid state temperature sensor.  It made thermister bridges obsolete.
>
>
> There is a difference between something like a platinum resistance
> thermometer (PRT or RTD) and a thermistor, but they both are "measure
> resistance to measure temperature" devices.
>
> Yes, the AD590 is a useful part (I've got some in a device being
> launched in August), but PRTs,thermistors, and thermocouples are still
> widely used.
>
> I don't know that the inherent precision (at room temperature)of the
> various techniques is wildly different.  A 1mV/K signal (AD590 into a
> 1k resistor) has to be measured to 0.1mV for 0.1 degree accuracy.
> That's out of 300mV, so 1 part in 3000
>
> A type E thermocouple is 1.495 mV at 25C and 1.801 at 30C, so about
> 0.06 mV/K slope. Measure 0.006mV for 0.1 degree  (plus the "cold
> junction" issue).  1 part in 250 measurement.
>
> Modern RTDs all are 0.00385 ohm/ohm/degree at 25C.  Typically, you
> have a 100 ohm device (although there are Pt1000s), so it's changing
> 0.385 ohm/degree.  1 part in 3000
>
> Checking the Omega catalog.. A 44007 has nominal 5k at 25C, and is
> 4787 at 26C, so 1 part in 24.
>
> Especially these days, with computers to deal with nonlinear
> calibration curves, there's an awful lot of TCs and Thermistors in
> use. The big advantage of the AD590 and PRT is that they are basically
> linear over a convenient temperature range.
>
> In a variety applications, other aspects of the measurement device are
> important - ESD sensitivity, tolerance to wildly out of spec
> temperature without damage, radiation effects etc.  Not an issue here,
> but I'll note that the thermistor, PRT, and thermocouple are
> essentially ESD immune. The AD590 most certainly is not.
>
> If you go out and buy cheap industrial PID temperature controller it
> will have input modes for various thermocouples and PRTs.  I suppose
> there's probably some that take 1uA/K, but it's not something I would
> expect.
>
> So I wouldn't say thermistor bridges (or other 

[time-nuts] Fwd: Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-04 Thread Donald E. Pauly
I stand by my remark that thermistors have been obsolete for over 40
years.  The only exception that I know of is cesium beam tubes that
must withstand a 350° C bakeout.  Thermistors are unstable and
manufactured with a witches brew straight out of MacBeth.  Their
output voltages are tiny and are they inconvenient to use at different
temperatures.

Where did you get the idea to use a 1 k load for an AD590?  If you run
it from a -5 V supply you can use a 15 k load to a +5V supply.  This
gives 15 V/C° output.  If you drive it from a 10 Meg impedance current
source, you get 30,000 V/ C°.  If I remember correctly, I drove a
power MOSFET heater gate directly in my prototype oven 20 years ago.
It would go from full off to full on in 1/15 ° C.  Noise is 1/25,000 °
C in a 1 cycle bandwidth.

The room temperature coefficient of an AT crystal is -100 ppb per
reference cut angle in minutes.  (-600 ppb/C° for standard crystal)
The practical limit in a crystal designed for room temperature is
about 0.1' cut accuracy or ±10 ppb/C°.  If you have access to an
atomic standard, you can use feed forward to get ±1 ppb/C°.  If the
temperature can be held to ±0.001° C, this is ±1 part per trillion.
This kind of accuracy has never been heard of.  Feed forward also
allows you to incorporate the components of the oscillator into the
thermal behavior.  It does no good to have a perfect crystal if the
oscillator components drift.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: jimlux 
Date: Sun, Jun 4, 2017 at 4:47 AM
Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
To: time-nuts@febo.com


On 6/3/17 9:56 PM, Donald E. Pauly wrote:

> It was only in the early 70s that Analog Devices invented the AD590
> solid state temperature sensor.  It made thermister bridges obsolete.


There is a difference between something like a platinum resistance
thermometer (PRT or RTD) and a thermistor, but they both are "measure
resistance to measure temperature" devices.

Yes, the AD590 is a useful part (I've got some in a device being
launched in August), but PRTs,thermistors, and thermocouples are still
widely used.

I don't know that the inherent precision (at room temperature)of the
various techniques is wildly different.  A 1mV/K signal (AD590 into a
1k resistor) has to be measured to 0.1mV for 0.1 degree accuracy.
That's out of 300mV, so 1 part in 3000

A type E thermocouple is 1.495 mV at 25C and 1.801 at 30C, so about
0.06 mV/K slope. Measure 0.006mV for 0.1 degree  (plus the "cold
junction" issue).  1 part in 250 measurement.

Modern RTDs all are 0.00385 ohm/ohm/degree at 25C.  Typically, you
have a 100 ohm device (although there are Pt1000s), so it's changing
0.385 ohm/degree.  1 part in 3000

Checking the Omega catalog.. A 44007 has nominal 5k at 25C, and is
4787 at 26C, so 1 part in 24.

Especially these days, with computers to deal with nonlinear
calibration curves, there's an awful lot of TCs and Thermistors in
use. The big advantage of the AD590 and PRT is that they are basically
linear over a convenient temperature range.

In a variety applications, other aspects of the measurement device are
important - ESD sensitivity, tolerance to wildly out of spec
temperature without damage, radiation effects etc.  Not an issue here,
but I'll note that the thermistor, PRT, and thermocouple are
essentially ESD immune. The AD590 most certainly is not.

If you go out and buy cheap industrial PID temperature controller it
will have input modes for various thermocouples and PRTs.  I suppose
there's probably some that take 1uA/K, but it's not something I would
expect.

So I wouldn't say thermistor bridges (or other temperature
measurements) are obsolete.
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-04 Thread Donald E. Pauly
I've bought dozens of them over the years and talked to crystal
engineers for tens of hours.  I watched them plated and tuned at a
crystal filter company in Phoenix.  I own Virgil Bottom's book on the
subject and understood half of it.

πθ°μΩω±√·Γλ
WB0KVV


-- Forwarded message --
From: Bob kb8tq 
Date: Sun, Jun 4, 2017 at 5:15 AM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement 
Cc: "rwa...@aol.com" , "Donald E. Pauly"



Hi

Have you ever tried to actually *buy* a crystal built to a
specification? There is a
tolerance on them. That has a profound impact on what you can *buy*.

Bob
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-04 Thread Donald E. Pauly
You have a fundamental misunderstanding of the AT curve family.  See
my QBASIC plot at
http://gonascent.com/papers/hp/hp5061/photos/newxtl.jpg .  The
commonly described AT cut is shown as the largest sine wave in the
blue rectangle.  The left side of the rectangle is -55°C, the center
is 25° C and the right side is 105° C.  The bottom of the rectangle is
-16 ppm and the top is +16 ppm.

Main Cut
Temp   Freq
-55° C -16 ppm
-15° C +16 ppm
+25° C ±0 ppm
+65° C -16 ppm
105° C +16 ppm

You can get a lower turnover point of 24° C and an upper turnover
point of 26° C. Their amplitude would be °±0.250 ppb.  As the turnover
points approach each other, their amplitude approaches zero.  The line
joining all the turnover points is y= -8·x^3.  The zero temperature
for 25° is y=4·x^3.  Practical tolerance these days is on the order of
0.1 minutes of arc.  This is within the width of the traces in the
graph.

You are way off on your 0° to 50° C crystal.

["Umm …. errr … it’s quite easy to get a +/- 2 ppm 0-50C AT cut
*including* the tolerance on the cut angle."]

Temp   Freq
 0° C   -0.488 ppb (lower limit)
12.5° C  +0.488 ppb (lower turning point)
   25° C  ±0
37.5° C  -0.488 ppb (upper turning point)
   50° C +0.488 ppb (upper limit)

As I claimed, a Thermal Electric Cooler has never been used to build a
crystal oscillator.  In the 50s, TEC efficiencies were on the order of
1% and were useless.  The Soviets made coolers more practical in the
70s with better materials.  I saw one used at Telemation that was able
to measure dew point by condensing water vapor on a mirror.  It looks
like efficiencies have now improved to 33% or so.

It was only in the early 70s that Analog Devices invented the AD590
solid state temperature sensor.  It made thermister bridges obsolete.
Switching amplifiers are required to drive thermal coolers if you want
to preserve efficiency.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Bob kb8tq 
Date: Fri, Jun 2, 2017 at 12:22 PM
Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies
To: "Donald E. Pauly" 
Cc: "rwa...@aol.com" , time-nuts 

Hi

Any real crystal you buy will have a tolerance on the angle. In the
case of a crystal cut for turn the temperature will be a bit different
and you will match your oven to it. If you attempt a zero angle cut,
you will never really hit it and there is no way to compensate for the
problem.

Bob

On Jun 2, 2017, at 3:19 PM, Donald E. Pauly  wrote:

A cut at that angle has no turn over temperature. The zero temperature
coefficient point is 25°.  Its temperature coefficient everywhere else
is positive.

On Friday, June 2, 2017, Bob kb8tq  wrote:
>
> Hi
>
> If you are going to use an oven, it’s better to run it at the turn 
> temperature of
> the crystal. That would put you above 50C for an AT and a bit higher still 
> for an SC.
>
> Bob
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[time-nuts] Fwd: Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-03 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-June/date.html

I am familiar with this effect.  My specialty is switching amplifiers
and I wrote the classic paper for Motorola on the subject, see
http://gonascent.com/papers/an1042.pdf .  Ripple in the dc from a
switching amplifier is less than a part per thousand.  These thermal
coolers have about a 10% efficiency which means it takes 10 Watts to
pump a Watt.  That is a tiny switching amplifier.  Ovens also require
several Watts if operated at -55° C.  Thermo coolers/heaters require
little power when operated close to room temperature.  Highest power
is required at high ambient temperatures.

πθ°μΩω±√·Γ
WB0KVV
https://www.febo.com/pipermail/time-nuts/2017-June/date.html
-- Forwarded message --
From: Bruce Griffiths 
Date: Fri, Jun 2, 2017 at 4:34 PM
Subject: Re: [time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies
To: jimlux , Discussion of precise time and
frequency measurement 


Thermomechanical fatigue can significantly reduce the lifetime of
Peltier devices if the ripple current flowing in the Peltier device is
too high. This can become an issue with switchmode drive to a Peltier
cooler.

Bruce


>
> On 03 June 2017 at 11:02 jimlux  wrote:
>
> On 6/2/17 2:51 PM, Donald E. Pauly wrote:
>
> > >
> > This is an improvement of 476 to 1. You apparently have not thought
> > thru what improvements are possible with thermal coolers/heaters.
> > Among these is near instant warm up and greatly reduced power for
> > thermal management.
> >
> > >
> without getting into the whole crystal issue, one of the advantages of a
> heater is that it can be VERY simple (and hence reliable, just on a
> parts count basis). With a decent package, once it's hot, the power
> required to keep it hot can be quite low.
>
> With a heat/cool, you need to be able to have a bipolar supply to the
> peltier device, and they're not particularly efficient (that is, to
> extract 1 Watt of heat, you're putting in significantly more than 1 watt
> of DC, and rejecting 1+X watts to the outside world.
>
> And then, if you use a linear power supply/amplifier to drive the
> device, that is probably a class A device, and somewhat lossy. A
> switcher would be more efficient, but then you have the problem of
> switching noise, in close proximity to the crystal. You could put a big
> low pass filter in, but now you're adding even more components.
>
> There are undoubtedly some cases where the thermoelectric scheme would
> work better - for instance, you have a system with a TCXO and it's
> really set up for the TCXO to be at 25C, and you want to regulate that.
>
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[time-nuts] Fwd: HP10811 Oscillator Thermal Fuse

2017-06-03 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-Jun/date.html

We finally got in the Panasonic thermal fuses for the HP10811 and have
a few extra.  They will either plug in or solder.  Contact me if you
need one.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Van Horn, David 
Date: Thu, May 11, 2017 at 7:01 PM
Subject: Re: [time-nuts] HP10811 Oscillator Thermal Fuse
To: Discussion of precise time and frequency measurement 

The original article was from Kodiak consulting.  Good thing I saved a copy.
Thanks for the link to this one.
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-02 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html

Electronic thermal coolers did not exist then so it could not be done.
Electronic temperature sensors did not exist either.  That crystal cut
has been known since the 1940's at least.  It has been neglected
because of limited temperature range. It yields ±1 ppm over a range of
±20° C from 25° C.  A slightly different angle of cut can yield ±250
ppb over that range. (4:1 improvement) Contrast that with a normal AT
cut which yields ±9 ppm over that range.

I built an oven with an Analog Devices temperature sensor 20 years
ago.  I did not have time to incorporate foam insulation.  The heater
power was not available to run it at 65° C without insulation.  It had
to run at 40° C and it would hold about 1 ppb over a few hours.   It
would hold the crystal within 0.01° or so but it was far away from the
turnover temperature.   Convection currents cause problems.  It
convinced me that ovens were headaches.   Thermal coolers remove most
of these.

πθ°μΩω±√·Γ
WB0KVV

-- Forwarded message --
From: Bob kb8tq 
Date: Fri, Jun 2, 2017 at 3:50 PM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement 
Cc: "rwa...@aol.com" , "Donald E. Pauly"



Hi

Have you checked out the papers from the 1950 and `1960’s where they
actually tried what you
propose with essentially the same parts you are looking at using?

Bob


> On Jun 2, 2017, at 5:51 PM, Donald E. Pauly  wrote:
>
> # 2 is not true.  A cut has either two turning points or zero.  Where
> both turning points exist there are two temperatures at which the
> temperature coefficient of frequency is zero.  Cut 0 on figure 6 at
> https://coloradocrystal.com/applications has no turnover point.  It is
> neither fish nor fowl.  Cut 6 is the normal AT curve with extremes of
> ±16 ppm for -55° C thru +105° C.  All curves normally intersect at 25°
> C rather than the 27° C shown.  25° C is half way between -55° C thru
> +105° C.  Curve 6 is the Tchebychev polynomial y=4x^3-3x and curve 0
> is y=4x^3.
>
> Consider the standard AT cut which has turnover points at -15° C and
> 65° C.  The lower turnover would ordinarily not be used in ovens.  A
> set point error of ±1° C in the upper turnover point at 65° C results
> in a frequency error of +14.875·10^-9.  For cut 0, that same ±1° error
> in room temperature results in a frequency error of  ±31.25·10^-12.
> This is an improvement of 476 to 1.  You apparently have not thought
> thru what improvements are possible with thermal coolers/heaters.
> Among these is near instant warm up and greatly reduced power for
> thermal management.
>
> πθ°μΩω±√·Γ
> WB0KVV
>
> On Friday, June 2, 2017, Bob kb8tq  wrote:
>>
>> Hi
>>
>> Any real crystal you buy will have a tolerance on the angle. In the case of 
>> a crystal cut for turn
>> the temperature will be a bit different and you will match your oven to it. 
>> If you attempt a zero
>> angle cut, you will never really hit it and there is no way to compensate 
>> for the problem.
>>
>> Bob
>>
> ___
> time-nuts mailing list -- time-nuts@febo.com
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-02 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html

Tell us more about the RF leakage problems in the 5061.  I thought
that the 5071 used the same beam tube.  How does the electricity leak
out and at what frequencies?My method costs a tenth as much and
has higher spectral purity performance to the beam tube.  I admit that
I hadn't thought about the electricity leaking out. Can the leak be
plugged?

BTW these are not strictly Diophantine equations.  No exact solution
is possible if C field is to be used.  Can you tell us the magic
numbers?

πθ°μΩω±√·Γλ
WB0KV


-- Forwarded message --
From: Richard (Rick) Karlquist 
Date: Fri, Jun 2, 2017 at 12:10 PM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement
, "Donald E. Pauly" ,
"rwa...@aol.com" 


I said no *manufacturer* does it this way.  NBS is not
a manufacturer.  In a one-off money-is-no-object non-portable
standard, you can make direct multiplication work.  It
will not work well in a 5061, because of RF leakage
issues specific to the 5061 that are well documented.
Bolting on a different synthesizer does nothing to change that.

The decision not to use direct multiplication has nothing to
do with not being able to figure out how to synthesize the
correct frequency.  Certainly by the time we did the 5071A,
we were already using DDS, and it wouldn't have been any
problem to synthesize for direct multiplication if we had
wanted to do that.  You seem to be doing it the hard way
(pre DDS) involving Diophantine equations.  So it's easier
to do direct multiply than it used to be, but that doesn't
necessarily mean you should do it that way.

Rick
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-02 Thread Donald E. Pauly
# 2 is not true.  A cut has either two turning points or zero.  Where
both turning points exist there are two temperatures at which the
temperature coefficient of frequency is zero.  Cut 0 on figure 6 at
https://coloradocrystal.com/applications has no turnover point.  It is
neither fish nor fowl.  Cut 6 is the normal AT curve with extremes of
±16 ppm for -55° C thru +105° C.  All curves normally intersect at 25°
C rather than the 27° C shown.  25° C is half way between -55° C thru
+105° C.  Curve 6 is the Tchebychev polynomial y=4x^3-3x and curve 0
is y=4x^3.

Consider the standard AT cut which has turnover points at -15° C and
65° C.  The lower turnover would ordinarily not be used in ovens.  A
set point error of ±1° C in the upper turnover point at 65° C results
in a frequency error of +14.875·10^-9.  For cut 0, that same ±1° error
in room temperature results in a frequency error of  ±31.25·10^-12.
This is an improvement of 476 to 1.  You apparently have not thought
thru what improvements are possible with thermal coolers/heaters.
Among these is near instant warm up and greatly reduced power for
thermal management.

πθ°μΩω±√·Γ
WB0KVV

-- Forwarded message --
From: Bob kb8tq 
Date: Fri, Jun 2, 2017 at 12:43 PM
Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies
To: "Donald E. Pauly" 

Hi

Which statement is not true:

1) That there is a tolerance on the cut angle of a crystal?

2) That true zero temperature coefficient only happens at the turn?

3) That heater based controllers are impossible to build?

Bob

On Jun 2, 2017, at 3:40 PM, Donald E. Pauly  wrote:

That is not true.  I say that thermal coolers have made ovens
obsolete.  A zero temperature coefficient at room temperature is
easier to hit than a zero temperature at the upper turnover point when
such a thing exists.  See
curve 0 in Figure 6 at https://coloradocrystal.com/applications/ .

πθ°μΩω±√·Γ
WB0KVV


On Friday, June 2, 2017, Bob kb8tq  wrote:
>
> Hi
>
> Any real crystal you buy will have a tolerance on the angle. In the case of a 
> crystal cut for turn
> the temperature will be a bit different and you will match your oven to it. 
> If you attempt a zero
> angle cut, you will never really hit it and there is no way to compensate for 
> the problem.
>
> Bob
>
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-02 Thread Donald E. Pauly
That is not true.  I say that thermal coolers have made ovens obsolete.  A
zero temperature coefficient at room temperature is easier to hit than a
zero temperature at the upper turnover point when such a thing exists.  See
curve 0 in Figure 6 at https://coloradocrystal.com/applications/ .

πθ°μΩω±√·Γ
WB0KVV


On Friday, June 2, 2017, Bob kb8tq > wrote:

> Hi
>
> Any real crystal you buy will have a tolerance on the angle. In the case
> of a crystal cut for turn
> the temperature will be a bit different and you will match your oven to
> it. If you attempt a zero
> angle cut, you will never really hit it and there is no way to compensate
> for the problem.
>
> Bob
>
> On Jun 2, 2017, at 3:19 PM, Donald E. Pauly 
> wrote:
>
> A cut at that angle has no turn over temperature. The zero temperature
> coefficient point is 25°.  Its temperature coefficient everywhere else is
> positive.
>
> On Friday, June 2, 2017, Bob kb8tq  wrote:
>
>> Hi
>>
>> If you are going to use an oven, it’s better to run it at the turn
>> temperature of
>> the crystal. That would put you above 50C for an AT and a bit higher
>> still for an SC.
>>
>> Bob
>>
>>
>
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-02 Thread Donald E. Pauly
A cut at that angle has no turn over temperature. The zero temperature
coefficient point is 25°.  Its temperature coefficient everywhere else is
positive.

On Friday, June 2, 2017, Bob kb8tq  wrote:

> Hi
>
> If you are going to use an oven, it’s better to run it at the turn
> temperature of
> the crystal. That would put you above 50C for an AT and a bit higher still
> for an SC.
>
> Bob
>
> > On Jun 2, 2017, at 2:09 PM, Donald E. Pauly  > wrote:
> >
> > https://www.febo.com/pipermail/time-nuts/2017-May/105566.html
> >
> > If we build this circuit it would be a bench model not designed to be
> > inside a hot chassis.  It would be able to lock ± 5° C of 25° C.  My
> > idea of an oven is to keep the crystal and oscillator at 25° C ±0.001
> > °C with 60 second warm up/cool down time.
> >
> > πθ°μΩω±√·Γλ
> > WB0KVV
> >
> > -- Forwarded message --
> > From: Bob kb8tq >
> > Date: Fri, Jun 2, 2017 at 5:57 AM
> > Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
> > To: Discussion of precise time and frequency measurement <
> time-nuts@febo.com >
> >
> > Hi
> >
> > I would suggest you check a few real crystals over the 20 to 40C range ….
> > With all the “stuff” in a 5061, it will change (rise) at least 10C
> > after turn on.
> >
> > Bob
> > ___
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> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
>
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-02 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html

If we build this circuit it would be a bench model not designed to be
inside a hot chassis.  It would be able to lock ± 5° C of 25° C.  My
idea of an oven is to keep the crystal and oscillator at 25° C ±0.001
°C with 60 second warm up/cool down time.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Bob kb8tq 
Date: Fri, Jun 2, 2017 at 5:57 AM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement 

Hi

I would suggest you check a few real crystals over the 20 to 40C range ….
With all the “stuff” in a 5061, it will change (rise) at least 10C
after turn on.

Bob
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-02 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html

A guy by the name of David W. Allan used direct multiplication to
build NBS-4 and NBS-5, see http://tf.nist.gov/general/pdf/65.pdf .  He
didn't see anything wrong with it.  He used a commercial frequency
standard modified from 5 mc to 5.006880 mc.  That in turn was
multiplied by 1836.  This was a multiplier chain of 2·2·3·3·3·17.
When multiplied to 9192 mc, this is 90 cycles low so the standard
would be forced high by 0.05 cps..  They measured the locked frequency
standard to determine the actual frequency of the cesium line.  I
propose NO multiplier chain.

What are the supposed problems in using a direct submultiple of the
cesium resonance?  It seems to me that all other techniques result in
more phase noise there.  I found the relationship 91.92631770
mc·(137,075/126,008)=99,999,999.98992 cps=100,000.000--0.01008 cps.
It is low by 0.1 ppb and therefore cannot be adjusted by C field
current.  The C field can only lower the frequency.  There is another
relationship that gives a higher frequency of a fraction of a part per
billion which is easily adjustable.  Perhaps HP was unaware that such
a frequency exists.

πθ°μΩω±√·Γλ
WB0KV


-- Forwarded message --
From: Richard (Rick) Karlquist 
Date: Thu, Jun 1, 2017 at 10:01 PM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement
, "Donald E. Pauly" ,
"rwa...@aol.com" 


Direct multiplication to 9192 MHz isn't used
by any manufacturer of any atomic clock that I
know of, due to its well known disadvantages.
I can state for a fact that it was summarily
rejected by the designers of the 5060/5061
(Cutler, et al).  In the 5071, I (being the
RF designer) also summarily rejected it.
The architecture that is instead used is indeed
complex and expensive as you say.  It is
also ACCURATE.

Rick


On 6/1/2017 7:04 PM, Donald E. Pauly wrote:
>
> https://www.febo.com/pipermail/time-nuts/2017-May/105566.html
>
> The lock system on the HP5071 is complex and expensive.  My plan to
> improve the HP5061B is to to use a pair of third overtone crystals
> running at 91.9 mc and 100 mc.  I have come up with the magic numbers
> to lock them together.  This eliminates all multipliers with the
> exception of the A4 board. The 12.61 mc synthesizer input presently
> wastes half the microwave power produced by the 90 mc input in the
> unused lower sideband. Therefore only half the 91.9 mc drive is
> required.
>
> Eight bit ECL dividers in one package are available to perform the
> necessary lock.  When multiplied by 100 to the cesium resonance line,
> the 91.9 mc frequency is a few cycles high so that C field currents
> are reasonable. With crystal cuts for zero temperature coefficient at
> 25°C, it is possible to get along without an oven.  Room temperature
> performance at 25°C±5°C is ±15·10^-9.  Oscillator warm up time would
> be measured in seconds.
>
> Square wave modulation of variable frequency and amplitude shows
> promise for reducing the noise effects of the beam tube.  You can
> smoothly change the lock time constant, deviation and frequency.  This
> would avoid the big disturbance of the HP5061B when you switch from
> OPR to LTC. (OPR=operate with 1 second time constant, LTC=operate with
> 100 second time constant)
>
> πθ°μΩω±√·Γλ
> WB0KV
> ___
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>
>
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-06-01 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105566.html

The lock system on the HP5071 is complex and expensive.  My plan to
improve the HP5061B is to to use a pair of third overtone crystals
running at 91.9 mc and 100 mc.  I have come up with the magic numbers
to lock them together.  This eliminates all multipliers with the
exception of the A4 board. The 12.61 mc synthesizer input presently
wastes half the microwave power produced by the 90 mc input in the
unused lower sideband. Therefore only half the 91.9 mc drive is
required.

Eight bit ECL dividers in one package are available to perform the
necessary lock.  When multiplied by 100 to the cesium resonance line,
the 91.9 mc frequency is a few cycles high so that C field currents
are reasonable. With crystal cuts for zero temperature coefficient at
25°C, it is possible to get along without an oven.  Room temperature
performance at 25°C±5°C is ±15·10^-9.  Oscillator warm up time would
be measured in seconds.

Square wave modulation of variable frequency and amplitude shows
promise for reducing the noise effects of the beam tube.  You can
smoothly change the lock time constant, deviation and frequency.  This
would avoid the big disturbance of the HP5061B when you switch from
OPR to LTC. (OPR=operate with 1 second time constant, LTC=operate with
100 second time constant)

πθ°μΩω±√·Γλ
WB0KV
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-05-31 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105554.html

Our attempt to measure the low frequency noise to determine the
possible lock improvement was a failure. We will have to get access to
the Loop Gain pot to get a flat signal at low impedance.  Beware of
low frequency roll off.

I found out that the feedback amplifier on the A7 board causes the
electron multiplier output to roll off above 19 cps.  It places an
8,200 pFd condenser across the 1 M load resistor which causes the roll
off.  Here is a linear sweep up to 8 kc.
http://gonascent.com/papers/hp/hp5061/waveform/wideswee.jpg  It shows
the 274 cps second harmonic as well as the 16 cps roll off.

Our previous posts involving various modulation schemes were correct
because we drove the scope directly from the electron multiplier.
While the meter driver is a convenient amplifier, you have to
disconnect C1 to prevent the low frequency roll off. The feedback
amplifier has a gain proportional to frequency.  This restores
flatness above 19 cps for the loop gain pot.  I got a gain of 141 at
137 cps with a lagging phase angle of 90°.  R10 is loaded by C1 which
drops the level at that frequency by 7:1.  Effective gain is about
20:1 on the Loop Gain pot in the hi gain position of S1.  Gain is
about 7 in the low gain position.  In both positions low frequency
roll off is about 19 cps.

πθ°μΩω±√·Γλ
WB0KV
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-05-29 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105500.html

We recently did a partial alignment of the lock servo on our #2
HP5061B after replacing the beam tube. The previous owner had tried to
fix it by turning adjustments.  This made a big improvement in the
lock.  KB7APQ got the idea to use the audio spectrum analyzer in his I
Phone to measure the noise output of the beam tube.

We used the Beam I meter driver emitter follower for an audio source.
It provides about 0.4 Volts per 25 uA on the meter.  A 100 ohm safety
resistor was in series with Q6 emitter on the A7 board.  It was
followed by a 100 nFd condenser into the 100 k input impedance of the
I phone.  Low frequency cutoff is about 16 cps.

See http://gonascent.com/papers/hp/hp5061/waveform/spectrum.jpg .
Start frequency is 4 cps and each bin is 8 cps wide.  Center frequency
of each bin is 8 cps higher than the one before it.  Frequency and
amplitude are both logarithmic.  Amplitude is 12 db per division.  The
first three bands show the low frequency rolloff of the coupling
condenser.  Five harmonics of the 137 cps modulation frequency can be
seen.

For unknown reasons, a sharp null in the noise of about 2 db at 137
cps is seen.  The servo nulls the 137 cps there but I can't see how
the noise could be nulled.  The prominent second harmonic at 274 cps
is normal.  It measures -74 db below reference.  I calculated it at
about 0.15 V pp or 53 mV rms.  The third harmonic at 411 cps again
shows up as a 2 db noise null for unknown reasons.The fourth harmonic
at 548 cps cannot be seen. The fifth harmonic at 685 cps barely breaks
thru the lower limit of the spectrum analyzer.

It looks like rectifier pulse harmonics can be seen at 120 cps.  They
may be getting thru the mu metal shields of the beam tube.  That
frequency is right on the border of two bins.  360 cps third harmonic
of rectifier pulses can be seen.  It appears in the middle of a bin.
An unknown signal is seen at 564 cps.  This could be the +3500 power
supply frequency.

1 cps bandwidth noise in the 50 to 100 cps area seems to be about 20
db below the 274 cps second harmonic.  This will determine the
possible lock improvement with improved modulation methods.

πθ°μΩω±√·Γλ
WB0KV


-- Forwarded message --
From: Bob kb8tq 
Date: Sat, May 27, 2017 at 6:01 PM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement 

Hi

Having run a 5071A with a *very* good 10811 in it, the OCXO does
dictate what happens at 0.1 seconds. Once you get past that, you are
headed into a bit of a gray zone. You are partly looking at the Cs and
partly looking at the OCXO. Pushing out the crossover between the two
could help you at 1 second. The gotcha is that the “hump” will still
be there, just a bit further out. The net effect at (say) 100 seconds
could easily be worse
with the “fix”.

Bob
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-05-27 Thread Donald E. Pauly
Tom:

The Greek letters are my pallet for common electronic letters.  I
transposed two items in my last post and here they are corrected.
Note that the √(frequency error)=ratio of Zeeman frequencies as well
as ratio of C fields.

model/freq error cps/Zeeman freq kc/C field/(milliGauss)

5061A 1.59 42.82 61 mG
5061B 2.50 53.53 76 mG
5062C 4.30 70.40 (100 mG?)

I am investigating the total redesign of the HP5061B lock system for
vastly improved performance.  It looks like the performance of the
HP5071A can be beaten by 10 to 1 for averaging times on the order of a
few seconds.

πθ°μΩω±√·Γλ
WB0KV

-- Forwarded message --
From: Tom Van Baak 
Date: Fri, May 26, 2017 at 5:36 PM
Subject: Re: HP5061B Versus HP5071 Cesium Line Frequencies
To: "Donald E. Pauly" 

Donald,

I'm enjoying many of your 5061 posts the past few months. Fun isn't
is? Thanks for taking the time sharing them with the group.

Question...

> πθ°μΩω±√·Γλ

What's that Greek mean (70 3F B0 B5 4F 3F B1 76 B7 47 3F)?

Thanks,
/tvb
Moderator, http://leapsecond.com/time-nuts.htm
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[time-nuts] Fwd: HP5061B Versus HP5071 Cesium Line Frequencies

2017-05-26 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html

Those were interesting links. C field levels are a small fraction of
the earth's field of 700 milliGauss.  The C field winding is a few
turns inside the beam tube.  They are driven by several different
possible currents depending upon the desired frequency correction.
For the HP5061B it is 24.5 mA for the standard tube at 100%.  At the
0% point of the C field, the cesium resonance is unaffected.  At the
50% point, it is shifted upward by the amount of error in the
microwave frequency.  This varies depending on synthesizer design.  At
the 100% point, the error is reversed to give a reverse adjustment
range equal to the original error.

An electron orbits in a magnetic field with frequency f=qB/(2πm).
(q=charge, B=field strength, m=electron mass)  The Zeeman frequency is
the same as the frequency of an electron orbit in a field equal to 25%
of C field listed.  The square of the C field gives the frequency
shift in the cesium line.  I saw 90 mG listed for the 5062C but I
think that it should be 100 mG.

There is a test for the beam tube when the rf drive is removed and the
LF coil is driven with a frequency equal to half the Zeeman frequency.
It induces a peak that checks the operation of the tube without rf.
Does anyone know what is actually going on then?  We had a bad beam
tube that failed this test.

model|freq error cps|Zeeman freq kc|C field|(milliGauss)
5061A 2.50 53.53 76 mG
5061B 1.59 42.82 61 mG
5062C 4.30 70.40 (100 mG?)

πθ°μΩω±√·Γλ
WB0KV


-- Forwarded message --
From: Tom Van Baak 
Date: Thu, May 25, 2017 at 9:23 PM
Subject: Re: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies
To: Discussion of precise time and frequency measurement 


Donald,

You're familiar with the 9,192,631,770 Hz definition of the SI second;
but that's only for an "unperturbed" atom. The bad news is that in
order to make the cesium beam operate at the central resonance peak
one actually has to violate the SI definition and perturb it -- by
applying a magnetic field (the so-called C-field), as well as other
factors. This cannot be avoided. The good news is that the shift can
be calculated.

In other words, because a magnetic field must be applied the actual
cesium resonance frequency is not 9192.631770 MHz. The synthesizer
locks to the peak, but the peak is at a slightly higher frequency than
the nominal book value. This detailed note from hp may help:

http://leapsecond.com/museum/hp5062c/theory.htm

Different model beam tubes use different field strength / Zeeman
frequency. Search the archives for lots of good postings about all
these magic frequencies -- google: site:febo.com zeeman

If you want to see what the resonance peaks (all 7 of them) actually
look after the C-field is applied see:

http://leapsecond.com/pages/cspeak/
and (poster size):
http://leapsecond.com/pages/cfield/

See also John's version:

http://www.ke5fx.com/cs.htm

One final comment -- the perturbed vs. unperturbed issue is far more
complex than a single correction. To get an idea of the math and
physics complexity of a laboratory Cs beam standard read some of
these:

http://tf.nist.gov/general/pdf/1497.pdf
http://tf.nist.gov/general/pdf/65.pdf
http://tf.boulder.nist.gov/general/pdf/101.pdf

/tvb

- Original Message -
From: "Donald E. Pauly" 
To: "time-nuts" ; "Donald E. Pauly" 
Sent: Thursday, May 25, 2017 7:55 PM
Subject: [time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies


https://www.febo.com/pipermail/time-nuts/2017-May/105298.html

The synthesizer in the HP5061B generates a frequency of about
9,192,631,772.5 cps when the 5 mc oscillator is exactly on frequency.
First the 5 mc oscillator is multiplied by 18 to 90 mc on the A1
board.  That in turn is multiplied by 102 in the A4 board to give
9,180 mc.

The 5 mc is also divided by 4079 to produce 1,225.790635 cps.  That in
turn is multiplied by 10,305 to produce 12,631,772.5 cps.  This is
added to the 9180 mc in the A4 mixer to produce the final frequency of
9,192,631,772.5 cps approximately.  This is higher than the defined
frequency of 9,192,631,770 cps by about 2.5 cps or 271·10^-12.  If I
figured it right, the C field adjustment only has a range of
40·10^-12.  This seems to be insufficient to put the standard on
frequency.

Can anyone explain these mysteries?  Does anyone know why this
frequency was chosen?  Does anyone know the choice for the frequency
of the HP5071 cesium?

πθ°μΩω±√·Γλ
WB0KV
4,079=prime
10,305=5x9x229
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[time-nuts] HP5061B Versus HP5071 Cesium Line Frequencies

2017-05-25 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html

The synthesizer in the HP5061B generates a frequency of about
9,192,631,772.5 cps when the 5 mc oscillator is exactly on frequency.
First the 5 mc oscillator is multiplied by 18 to 90 mc on the A1
board.  That in turn is multiplied by 102 in the A4 board to give
9,180 mc.

The 5 mc is also divided by 4079 to produce 1,225.790635 cps.  That in
turn is multiplied by 10,305 to produce 12,631,772.5 cps.  This is
added to the 9180 mc in the A4 mixer to produce the final frequency of
9,192,631,772.5 cps approximately.  This is higher than the defined
frequency of 9,192,631,770 cps by about 2.5 cps or 271·10^-12.  If I
figured it right, the C field adjustment only has a range of
40·10^-12.  This seems to be insufficient to put the standard on
frequency.

Can anyone explain these mysteries?  Does anyone know why this
frequency was chosen?  Does anyone know the choice for the frequency
of the HP5071 cesium?

πθ°μΩω±√·Γλ
WB0KV
4,079=prime
10,305=5x9x229
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[time-nuts] HP5061B Modulation Adjustment

2017-05-17 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html

The first time that we worked with this HP10514A mixer we had an HP105
oscillator to provide the 5mc comparison against our #1 cesium clock.
Stability was not good enough to get closer than a few hundred
picoseconds.  We expected some diode drift but not at that level. We
could not see a hot finger on a diode in the mixer. One millivolt out
of the mixer is about 31 picoseconds phase change near quadrature at
the drive levels used then. (±1 V peak dc)  The theoretical dc output
is sin θ where θ is the phase angle between inputs.  Two volts pp of
10 mc rides on that dc.  We were operating unterminated on the output
of the mixer.

As long as the diode drops are stable, we can still see phase changes
to a fraction of a picosecond.  A picosecond is the delay in an 8 mil
length of RG58 cable. (1,500 ps per foot)  We have one DVM with a
resolution of 1 μ V dc.  The data sheet on the mixer is at
http://gonascent.com/papers/hp/hp10514a.pdf .  We would appreciate
anyone who has experience on diode drift on these types of mixers to
post accordingly.  We built a 400 kc five pole low pass Butterworth
filter yesterday that removes the 10 mc from the mixer output.
(CLCLC)  Attenuation is about 10 million to one at 10 mc which reduces
the rf to about 0.1 μV peak to peak.  We can now see phase changes on
the oscilloscope of a few picoseconds at 1 mV per division.

The modulation deviation is hard to see at 5 mc and there is no handy
output there to drive a mixer.  We therefore drove our mixer with the
90 mc outputs of each HP5061B.  We used 6 db 50 Ω attenuators ahead of
the L and R inputs to avoid mixer overload. In phase dc out was about
0.5 V and 180° out of phase was about -0.5 V dc and was terminated in
50 by the low pass filter and the scope.  We ran both HP5061B's in
open loop with modulation on one of them on and the other one off.
See http://gonascent.com/papers/hp/hp5061/waveform/90mcmod.jpg .  This
shows the 137 cps modulation.  Note that there is a fair amount of
noise present. This contributes to noise in the final lock.
Modulation from cesium #2 was 16.9 mV pp and #1 was 13.9 mV pp.  The
#2 is about ±0.968° lead and lag or ±29.8 ps at 90 mc.  Modulation is
at 137 cps.  Phase change in a half cycle of the modulation is 2x 29.8
ps in 1/274 sec or 16.3 parts per billion average rate of phase
change.  Average phase change for a half cycle of a sine wave is 2/π
(0.636) times peak phase change. Peak phase change is therefore ±25.7
ppb or ± 2.31 cps at 90 mc.

The 90 mc is multiplied in the A4 mixer by 102 to 9180 mc.  At that
frequency the deviation becomes ± 236 cps or 472 cps peak to peak.
This is roughly the 550 cps distance between the cesium atomic
resonance at 9,192,631,770 cps and the valley either side of it.  We
have not disturbed the modulation adjustment on our #1 machine which
is 82% of the deviation of #2.  We will correlate the HP modulation
adjustment method with our measurements.  It seems to me that over
deviation of the modulator will increase the noise of the system.  Has
anyone experimented with lower modulation and higher gain on A7 board?
 We can easily see any improvement with our mixer.

We are familiar with the 2nd harmonic gain pot but have decided that
the instrument needs a complete alignment after the beam tube change.
We do not know how many knobs were turned trying to get it to work
with a bad beam tube.  It needs an alignment like it would have gotten
after it was built in the factory.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Bob kb8tq 
Date: Wed, May 17, 2017 at 4:05 AM
Subject: Re: [time-nuts] HP5061B Modulation Adjustment
To: Discussion of precise time and frequency measurement 
Cc: "rwa...@aol.com" , "Donald E. Pauly"


Hi

Keep in mind that the mixer has millivolt level offsets and millivolt level
drift (over a wide range).

There is a gain pot that “sets” the second harmonic. It can be low and the
device will still lock.

Bo
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[time-nuts] HP5061B Modulation Adjustment

2017-05-16 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/105298.html

We recently got our second HP5061B to lock after changing the beam
tube. We did no alignment with the exception of changing the gain on
Beam current.  Ion current dropped from 14 to 1 with only a few hours
of operation of the instrument.  We obtained momentary lock but lost
it after a couple of minutes.  The trouble was a blown themal fuse on
the HP10811 oscillator which shut down the oven.  We have TEMPORARILY
jumpered it while the correct fuse is on order.

We aligned the C Field on #1 but have not done that alignment on #2 yet.
The 5 mc output of our #1 instrument was compared to the 5mc output of
#2 with an HP10514A balanced mixer. Two input ports L and R are
multiplied by internal Shottky diodes to produce an X output which can
be terminated in 50 Ω. Maximum input current on both the L and R port
is 40 mA or 2 V rms.   One instrument was put in Open Loop and the
fine frequency adjusted to approach quadrature. It was then returned
to OPR and steered to final quadrature with the C Field.

We used a digital voltmeter with a resolution of 10 uV dc to measure
the X output of the mixer with the L and R inputs in near quadrature.
The mixer output contains a large 10 mc component of about 2 V peak of
peak which rides on the dc representing the phase difference. The dc
output for in phase and out of phase inputs is about +1 and -1 Volts.
Our calculated sensitivity was 31 uV per picosecond of error when
within a few degrees of quadrature. Lock within a few picoseconds was
obtained by adjusting C field on #2.  It had to be continuously
manually steered.  We could not look at the X output on the scope
because of the large rf level present.  Our digital meter might have
been experiencing rf overload causing inaccuracy at low dc voltages.

Continuous lock was lost a few times on #2 which we attributed to it
needing a complete alignment.  Second harmonic was only 22.  The
procedure in 5-217 g for modulation adjustment is not very scientific.
It calls for adjusting modulation for maximum 137 cps out of the AC
amplifier board when the beam tube is driven at 5x10^-9 below the
resonance line.  Modulation is then to be reduced by 5%.  This affects
all other adjustments.

We decided to directly measure this deviation with precision.  The
phase noise of the 90 mc output of the A3 multiplier board was
measured as well as the modulation.  The spectral width of our
function generators at 5 mc was compared to the HP5061B 5 mc output.
Our adventures with this project will be covered in a separate post.

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] HP10811 Oscillator Thermal Fuse

2017-05-11 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

While I find traces of your article quoted, it seems to have vanished.
It lead me to this interesting article of 16 pages on electronic fires
by a fire investigator.  There is a lot here for designers when it
comes to preventing fires from your products.  I would never have
dreamed of some of the ways that fires can start.

http://dri.org/docs/default-source/dri-online/course-materials/2016/fire-science/08-dangerous-things-come-in-small-packages.pdf


πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Van Horn, David 
Date: Thu, May 11, 2017 at 4:31 PM
Subject: Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse
To: Discussion of precise time and frequency measurement 


There's an excellent article out there on the web called "Low Voltage,
the incompetent ignition source"  I highly recommend a read.
I dealt with a case like this a couple years ago.  Failed fet in an H
bridge caused a fault which the brick SMPS picked up as a short, and
went into "hiccup" mode on.
The energy delivered in "hiccup" mode was about 1W average, and that
was enough, after several hours, to cause ignition and sustained flame
on the PCB.

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[time-nuts] Fwd: time.gov

2017-05-11 Thread Donald E. Pauly
Be sure to post your result. Five years ago I regularly checked my
Casio LED watch which was holding 0.3 seconds per week.  It always
worked properly.   Perhaps we should report this to Trump so he can
fire the head of NIST.

-- Forwarded message --
From: Jerry Hancock 
Date: Thu, May 11, 2017 at 4:52 PM
Subject: Re: [time-nuts]  time.gov
To: Discussion of precise time and frequency measurement 
Cc: "Donald E. Pauly" 


I checked it on two different computers and again just now, all were
counting 5+ seconds slow.  I then downloaded their flash app which as
an option I never had to do and that was correct.  Both of the apps
claim to be adjusted for network delay.

This was around 14:00Pacific.  I just checked again and both apps are
now correct.  I’ll have to dig into the issue.


> On May 11, 2017, at 3:09 PM, Donald E. Pauly  wrote:
>
> https://www.febo.com/pipermail/time-nuts/2017-May/date.html
>
> About 10 years ago, I checked my WWVB time code receiver that I built
> against time.gov and it was within 0.1 seconds.  That was as close as
> the eyeball can tell.  You report a huge error and if confirmed, you
> should complain.  I would double check against WWV since WWVB is now
> worthless for time comparison.  That webpage is supposed to be
> compensated for network delay within 0.1 second.
>
> Just now at 15:00:00 MST I checked my phone with time.gov on wireless
> versus a full size computer also on wireless.  I momentarily saw the
> phone 65 seconds ahead of the computer.  After hitting refresh and
> going off wireless and directly to my carrier, the phone matched the
> computer.  I had a witness but cannot get the problem to reappear.  I
> don't know exactly why the problem went away.  Some servers may cache
> web pages so refresh may be necessary.
>
> πθ°μΩω±√·Γλ
> WB0KVV
>
> -- Forwarded message --
> From: Jerry Hancock 
> Date: Thu, May 11, 2017 at 2:36 PM
> Subject: [time-nuts] time.gov
> To: Discussion of precise time and frequency measurement 
>
>
> I went to time.gov today as I was sitting away from my lab when a new
> watch arrived.  Finally got the 25yr watch from the company that laid
> me off a week later…
>
> Anyway, I set the seconds rollover to 00 when time.gov reset and then
> walked down to my lab and noticed the watch is now 6 seconds slow.  So
> I checked again with another computer, same problem, www.time.gov is 6
> seconds slow.  Never say this happen, usually it is right on the money
> give or take about .2 seconds.
>
> Jerry
> ___
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[time-nuts] HP10811 Oscillator Thermal Fuse

2017-05-11 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

These oscillators sold for $800 in 1985 or so.  They are on eBay all
working for $250 or more.  Where are all the ones with blown thermal
fuses for $25?  I want to buy.  It would be interesting to have the HP
warranty data for nuisance blows.  The three reported fire preventions
would have paid for the labor on all of the reported nuisance blows.
This is not to excuse the HP design error of picking a thermal fuse
temperature too close to the operating temperature.  Smoke damage
could do thousands of dollars of damage to a HP5061B or and expensive
microwave instrument.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Bob kb8tq 
Date: Thu, May 11, 2017 at 4:28 PM
Subject: Re: [time-nuts] HP10811 Oscillator Thermal Fuse
To: Discussion of precise time and frequency measurement 

Hi

A bit in jest:… that compares to 3,957 incidences of open fuses that
had nothing to do with
a thermal runaway. Of those, the majority 3,721 resulted in the 10811
being tossed
in the garbage as “another junker”……(yes, those are estimates, but I’d
bet they are close
based on the number of 10811’s made and how flakey those fuses are).

Bob
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Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse

2017-05-11 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

This is the third report of an open thermistor which would have
resulted in a fire in an HP10811 oven.  There are a dozen other
problems that could cause such a fire.  See
http://gonascent.com/papers/hp/hp10811/thermal.jpg .  The leads are
long enough that they can be soldered quickly without a heat sink if
the socket is to be replaced for better reliability.  A hemostat can
also be used to heatsink the leads one at a time.  We have the 108° C
fuse which is prone to nuisance blows.  HP has superceded it with a
125° C version.  Panasonic seems to make a direct replacement.  It is
stocked by Digikey for under a dollar.  I can find no reports of a
nuisance blow of the 125° version of the thermal fuse in a HP10811.
All nuisance blows seem to be in the 108° version.

In the 1970s, many consumer electronic products with 60 cps power
transformers had a thermal fuse inside them.  I bought a Sony real to
real stereo tape deck which was not working with that problem.  It was
a nuisance blow since no problems existed in the tape deck.  I
installed a fine gauge piece of solder since the fuse was close to
180° C.  I used it for over two years with no problems.

Later model switching power supplies have windings of several volts
per turn.  Shorts in these transformers will blow the fuse or destroy
the switching transistors.  A 60 cps transformer operates at a small
fraction of a volt per turn. A few shorted turns in a will not draw an
excessive primary current but merely causes a hot spot.  The hot spot
will grow as additional turns short.  Line current will not be greatly
excessive even as the transformer heats up.  It can catch fire well
before the fuse blows.

I saw a living room that caught fire because of a 60 cps transformer
in a stereo receiver.  The line breaker never tripped.  But for the
grace of G-d, the house would have burnt down.  A thermal fuse in the
transformer would have prevented several thousand dollars of damage.
That would have paid for over a thousand thermal fuses.

πθ°μΩω±√·Γλ
WB0KVV

 Forwarded message --
From: David G. McGaw 
Date: Wed, May 10, 2017 at 8:20 PM
Subject: Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse
To: Discussion of precise time and frequency measurement 

I too have had a fuse open up due to a failed thermistor in a HP10811.

David N1HAC
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[time-nuts] time.gov

2017-05-11 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

About 10 years ago, I checked my WWVB time code receiver that I built
against time.gov and it was within 0.1 seconds.  That was as close as
the eyeball can tell.  You report a huge error and if confirmed, you
should complain.  I would double check against WWV since WWVB is now
worthless for time comparison.  That webpage is supposed to be
compensated for network delay within 0.1 second.

Just now at 15:00:00 MST I checked my phone with time.gov on wireless
versus a full size computer also on wireless.  I momentarily saw the
phone 65 seconds ahead of the computer.  After hitting refresh and
going off wireless and directly to my carrier, the phone matched the
computer.  I had a witness but cannot get the problem to reappear.  I
don't know exactly why the problem went away.  Some servers may cache
web pages so refresh may be necessary.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Jerry Hancock 
Date: Thu, May 11, 2017 at 2:36 PM
Subject: [time-nuts] time.gov
To: Discussion of precise time and frequency measurement 


I went to time.gov today as I was sitting away from my lab when a new
watch arrived.  Finally got the 25yr watch from the company that laid
me off a week later…

Anyway, I set the seconds rollover to 00 when time.gov reset and then
walked down to my lab and noticed the watch is now 6 seconds slow.  So
I checked again with another computer, same problem, www.time.gov is 6
seconds slow.  Never say this happen, usually it is right on the money
give or take about .2 seconds.

Jerry
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[time-nuts] Fwd: Fwd: HP10811 Oscillator Thermal Fuse

2017-05-10 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

In order to have a runaway trophy, the thermal fuse would have to have
been jumpered and then an oven control failure would have to have
occurred.  The rated temperature of 125° C is well above operating
temperature of 82°C.  The thermal fuse can easily be soldered in by
heat sinking the leads where they enter the fuse.  The leads are
plenty long enough. I have done this dozens of times on Amana
microwave ovens in the late 70s. The venerable HP105 oscillator
contains a thermal fuse in both the fast warmup heater and the
proportional heater.

"3-8 Each heater circuit contains a thermal fuse to prevent damage to
components within the oven due to overheating."

I hadn't thought about smoking the styrofoam which melts at 240° C.
https://en.wikipedia.org/wiki/Polystyrene#Extruded_polystyrene_foam I
calculate that the oven could reach at least 208° C at the rated 71° C
ambient.Solder melts at 180° C.  Each power transistor has around
10 Volts across it and might even reach 300° C without destruction.
Many oscillators are operated above 20 Volts for the heater supply.
We have two reports of open thermistors in which disaster was avoided
by the thermal fuse blowing.


πθ°μΩω±√·Γλ
WB0KVV



-- Forwarded message --
From: Richard (Rick) Karlquist 
Date: Wed, May 10, 2017 at 5:34 PM
Subject: Re: [time-nuts] Fwd: HP10811 Oscillator Thermal Fuse
To: Discussion of precise time and frequency measurement 


The view from inside HP when I worked with the people
who designed and built the 10811 some 35-40 years ago
was that:

1.  10811 ovens rarely fail.

2.  When they do fail, it is rarely because the oven
runs away.  I know I have never encountered a runaway.
No one at HP had a "trophy" on their desk of a runaway
10811.  People tend to collect stuff like that.  One
engineer did have a 10811 with a 45 caliber bullet
fired through it (long story).

3.  From a business perspective, a failure is a failure
and so there is no business reason to have a fuse.

4.  Because the fuse could not be soldered in, it had
to be socketed, and the socket failures exceeded any
oven runaways by a good margin.  Therefore, it made
the "failure rate" worse.  That is all that matters to
the bean counters.

5.  The one and only reason it was in there at all
was the concern about toxic gases being released from
the foam.  Even without a runaway, foams tend to have
a "slow burn" and outgas "stuff" all the time.  Various
foams were evaluated to balance that issue with thermal
resistance and with the big issue with foam which is
mechanical fatigue.  This is similar to the wear out
of foam mattresses.

What should have been done with the thermal fuse would
have been to put crimp lugs on the leads and attach
the crimp lugs with screws.  However, there was no space
for all that stuff.

Rick N6RK
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[time-nuts] Fwd: HP10811 Oscillator Thermal Fuse

2017-05-10 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

The poster at 
http://www.simonsdialogs.com/2016/09/a-thermal-fuse-and-hp-10811-60111-repair/
reported that the thermal fuse saved an oscillator from destruction
when a thermistor opened.  HP made thousands of these which sold for
$800.  If a large portion failed it would have been addressed.  They
raised the temperature of the thermal fuse to reduce nuisance blows.
I say that nuisance blows equal to real blows are worth the trouble.
You may be getting oscillators on the surplus market or eBay which
have a higher proportion of nuisance blows.

πθ°μΩω±√·Γλ
WB0KVV

From: Mike Feher 
Date: Tue, May 9, 2017 at 9:10 PM
Subject: Re: [time-nuts] Fwd:  HP10811 Oscillator Thermal Fuse
To: Discussion of precise time and frequency measurement 

Respectfully I disagree. I have totally shorted out numerous
oscillator’s fuses with no problems. The design of those thermal fuses
makes them vulnerable to opening just due to years of use without
problem, in any of the electronics. My shorted out oscillators still
work. Ideally, if handy, it is easy enough to replace them if one is
available. They just plug in. If there is a thermal runaway, that
caused the opening, to me that implies that there are other issues.
Regards – Mike

Mike B. Feher, N4FS

89 Arnold Blvd.

Howell, NJ, 07731

848-245-9115
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[time-nuts] Fwd: HP10811 Oscillator Thermal Fuse

2017-05-09 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

I disagree about permanently jumpering the thermal fuse.  The
oscillator is rated down to -55° C and the oven can maintain 82° C at
that temperature.  This is a 137° C rise.  It is likely capable of
more heat than that.  At 25° C, it would therefore be able to reach at
least 25+137=162° C.  This is near solder melting temperature and
would quickly cook the components.  It is rated to work at 71° which
would give a temperature of 208° C and do serious damage.  That
thermal fuse is very important.  There are a dozen failures which
could result in a thermal runaway.

This web page discusses the fact that a thermal fuse should be 30° C
above normal operating temperature to prevent nuisance blows.
http://www.simonsdialogs.com/2016/09/a-thermal-fuse-and-hp-10811-60111-repair/
HP originally used a 26° C margin and later changed it to a 33°
margin.  This explains the frequent failures.  This poster used the
wrong type of fuse but the correct type is commercially available.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: Bob kb8tq 
Date: Mon, May 8, 2017 at 6:07 PM
Subject: Re: [time-nuts] HP10811 Oscillator Thermal Fuse
To: Discussion of precise time and frequency measurement 
Cc: "Donald E. Pauly" 

Hi

You will get a lot of diversity of opinion on the topic of the thermal
fuse on the 10811. My feeling is that they are a nuisance and
contribute very little to the design. I’d just short it out and move
on. In the era of failure prone heater transistors or faulty
thermistors, the fuse may have made sense. That era ended before the
10811 went into production.

Bob
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[time-nuts] HP10811 Oscillator Thermal Fuse

2017-05-08 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-May/date.html

We got a new beam tube for our #2 HP5061B cesium clock.  When the tube
was changed, it momentary locked for a couple of minutes but then
unlocked.  The oscillator had been set on frequency with our #1
HP5061B a while back but it was suddenly 100 cycles low at 5 mc.
Oscillator oven current was normal at 38.  This oscillator is used on
many other HP instruments such as counters.

KB7APQ tore apart the HP10811 oscillator and found that the thermal
fuse was open in the oven heater.  We think that it was a nuisance
blow.  Does anyone have any experience on this thermal fuse?  Digikey
seems to have
one that will work for under a dollar at
https://www.digikey.com/product-detail/en/panasonic-electronic-components/EYP-05BE115/P10907-ND/295803
.  We temporarily jumpered the fuse, the oscillator came right up on
frequency and we got our first lock.  We watched the actual oven
current go down when it reached operating temperature.  The oscillator
oven current indication is useless on the HP meter since it is not
actual oven current.

I found this post:

[https://groups.google.com/forum/#!msg/rec.radio.amateur.homebrew/g3Up39Wljak/DGr8OeLdz2gJ

I dug out my notes to find out the specifics.  My counter is an HP 5334B
with Option 1, the high stability oscillator.  The oscillator is one of
the HP 10811 series.  The original thermal fuse, F1, was rated for 108
degrees C.  HP revised the part to one rated for 115 degrees C, part
number 2110-0617 (10811-80003).

The Radio Shack thermal fuse was 270-1322A, rated for 128 degrees C.
There is also an NTE Electronics NTE8115, "Thermal Cut-Off", rated for
117 degrees C.  Either is larger than the HP part, and is a tight fit.
I wrapped them in electrical tape to protect against short circuits.
When soldering to the high-value resistors, I clamped the fuse leads in
a pair of pliers held with rubber bands.

Of course this may not apply to your counter if it doesn't have the
crystal oven!

Fred
K4DII]

Does anyone have any experience on this thermal fuse or words of wisdom?

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] HP5061B Cesium Tube Resonance

2017-04-21 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html

Yesterday we swept our HP5061B thru the cesium resonance curve.  As
far as I know this is the first time that the curves have been
published.  The original phase modulation is a very unlinear sine wave
frequency sweep.  We built a 100 ms time constant integrator for the
20 cps triangle from the function generator.  When a triangle is
integrated, the result looks much like a sine wave but it is not.  It
is really back to back parabolas as shown in
http://gonascent.com/papers/hp/hp5061/waveform/dblepara.jpg . The
waveform is actually inverted in the display.  Note that it appears a
bit squashed.  That small difference results in a linear triangle
frequency sweep. We drove J1 on the A3 board with the output of the
integrator and turned R20 the Mod Level pot all the way up.  The phase
modulation differentiates the output of the integrator to restore
linear sweep.

We ran the electron multiplier output J1 which went into the A7 board
into scope channel two see
http://gonascent.com/papers/hp/hp5061/waveform/csweep.jpg   Vertical
was 5 millivolts per division inverted.  Ground is shown by the yellow
1 arrow and the scope amplifier was providing the 1 MΩ termination.
The corresponding peak beam current is 20 nA or 20 on the HP meter.
Because of the varactor polarity, the frequency sweep is inverted and
is from -1,200 cps below resonance to +1,200 cps above resonance.  The
center of the negative going sweep of the triangle is the peak
response of the cesium tube while being swept from low to high
frequency.  At -550 cps below it and +550 cps above it are seen the
two valleys of the main resonance peak.  The center of the positive
going sweep of the triangle is also the peak response of the cesium
tube while being sweep from high to low frequency.  The valleys either
side of the main peak are seen again along with partial false peaks.

As you approach the positive peak of the triangle the lower false peak
is seen.  As you approach the negative peak of the triangle, the upper
false peak is seen.  Integrator limitations kept us from having enough
drive levels to see the complete lower and upper false peaks.
Remember that the sweep is reversed at both peaks of the triangle, low
to high and high to low.  See the artists depiction at Figure 4-43 in
the manual.

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] HP5061B Square Wave Modulation Evalukation

2017-04-13 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html

We did some testing to evaluate the advantages of square wave
modulation instead of sine waves for locking to the atomic resonance
peak.  We drove J1 on the A3 board with a 2.8 Volt peak to peak
triangle at 20 cps from a signal generator.  The crystal oscillator
fine frequency was adjusted downward for below resonance. See
http://gonascent.com/papers/hp/hp5061/waveform/sqrmod.jpg .

The frequency out of the phase modulator is proportional to the
derivative of the varicap voltage drive.  For the triangle rising
slope, the varicap is linearly increasing in capacitance with an
constantly increasing phase lag.  For the falling slope it is linearly
decreasing in capacitance and a constantly increasing phase lead.
This results in a lower and higher frequency for the positive and
negative slope of the triangle respectively.   The frequency shifts
suddenly from about 300 cps below resonance to about 100 cps above
resonance.  We performed the same measurements with the fine frequency
centered and above resonance but did not photograph them.

Back of the envelope calculations predict a 10:1 improvement in jitter
with square wave lock for average measurement times of 1 second.  Beam
current was injected directly into the scope with its 1 Meg resistance
being the load for the electron multiplier.   The scope was inverted
to give a positive appearing beam current of 5 nA per division.  Peak
beam current is about 22 nA. (nA=Beam I meter reading)  Note that the
beam current is slightly delayed from the triangle and contains
positive spikes at both transitions.  This originates from the 1
millisecond or so travel time of the beam from the start of the
microwave path to its end.  During the rising portion of the triangle,
the frequency out of the phase modulator is lowest and slightly below
resonance.  During the falling portion, it is the highest and slightly
above resonance.

When the frequency suddenly shifts, the beam cannot react instantly
because it is only traveling at the speed of sound and must travel a
foot or so in the microwave path.  This takes on the order of a
millisecond. A positive spike is created  as the frequency passes thru
the resonance peak at 22 nA. This occurs at both the low to high
transition and the high to low transition.   The frequency changes so
fast that the voltage cannot reach 22 nA.  As the center frequency is
reduced, the negative half of the square wave becomes more negative
and the positive half becomes more positive.  As the center frequency
is increased the square wave negative half becomes less negative and
the positive half becomes less positive.

When the center frequency is at the resonance of the cesium line the
square wave disappears except for the spikes.  Above center frequency,
it reverses phase and gradually gets bigger.  This type of lock is
nearly 100% efficient and should be far lower noise.

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] HP5061B Cold Start

2017-04-08 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html

We performed an experiment with our working HP5061B which had been
cold overnight.  This was to better determine lock time from cold
ovens.  We found that the crystal oscillator oven heats up about twice
as fast as does the cesium oven.  Therefore the lock time is not much
different whether the crystal oscillator was cold or hot.  Our crystal
oven has been running 34 when hot.  The cesium oven has been running
about 14 when hot.  Here is our data as a function of measurement time
in minutes versus meter readings.  "+" denotes a pegged meter.

The instrument was powered on at 0 minutes except for the cesium
heater.  The cesium heater was turned on at 13 minutes. The crystal
oven had nearly stabilized by that time.  Oscillator heater current
was stable 15 minutes after power up and undershoots a bit at about 23
minutes.

Note that first signs of beam current occur 7 minutes after cesium
oven was powered up.   First signs of 2nd harmonic occurred 9 minutes
after cesium oven was on.  We conclude that lock is feasible 23
minutes after a cold start.  If the crystal oven is left on, lock can
likely be achieved 20 minutes after the cesium oven is powered up.
The ion pump preserves beam tube vacuum if the crystal oven is left
on.  If it is left off for long periods, high ion pump current may
delay the application of power to the cesium oven until the vacuum is
pumped down.

For those who only occasionally need the stability of a cesium clock,
you can have full performance 23 minutes after a cold start, or 20
minutes if the crystal and the ion pump are hot.  If you use cesium
for an hour a day, tube lifetime will be extended by 24 to 1 over
continuous operation.  If a beam tube lasted five years in continuous
operation, it will last 120 years if used an hour per day.  A similar
benefit will occur if you use it continually for 2 weeks once a year.
It does no good to waste cesium unless you are using the instrument.

Time Ces Osc Beam 2nd

 0   +  0  0  0
 7   +  0  0  0
11 55  0  0  0
13 40  + 0  0
15 42 34 0 0
20 42 34 2 0
22 42 32 6 2
23 25 32 10 5 no lock
24 19 32 12 9 lock (free run back to OPR)
28 19 34 20 34 normal beam current
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[time-nuts] Fwd: HP5061B High Ion Current/Tubes Out of Cesium

2017-04-07 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html

We did not attempt to achieve lock because we saw absolutely no beam
current with the beam adjust all the way up.  We were running the oven
above 150° C which is more than 65° above normal oven temperatures.
Cesium pressure should have been about 30 times normal.

A photo of the A11 Cesium controller board is posted at
http://gonascent.com/papers/hp/hp5061/photos/cesiheat.jpg taken by
KB7APQ.  Note that there are no electrolytics but tantulums installed
instead.  They must have been very costly 30 years ago.  This also
prevents hard to find problems with high ESR electrolytics with age.
We have found open 47 μFd electrolytics inside two of our four HV
power supplies.  That is a place for tantalums if there ever was one.

We are working on our HP5061B's from 500 miles apart so photographs of
boards and waveforms help greatly.  The cesium oven servo is
underdamped.  It overshoots and rings down at a 10 second time
interval during temperature steps.  You can see the R12 that we
shorted out to get 150° oven temperatures for troubleshooting our
suspected bad tube.

I think that a website should be started with the collected wisdom of
this list.  I will host it if someone will maintain it. Corby's photo
graphs of dismantled beam tube parts should be on a nice web page.
If anyone has a high ion current 05061-6077 beam tube that they can
part with please contact me.  One of our beam tubes is completely out
of cesium.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: paul swed 
Date: Thu, Apr 6, 2017 at 5:09 PM
Subject: Re: [time-nuts] HP5061B High Ion Current/Tubes Out of Cesium
To: Discussion of precise time and frequency measurement 

Donald running higher temperatures on a a normal tube may indeed give you a
bit more life. Thats exactly how Frankenstein works. Its a hand me down
tube that normally showed as dead. Believe me it doesn't even move the
current meter and its working. My firm belief is that option 004 tubes do
not have anything left to give.

But yet with the higher temp (10-15 higher as I recall) it locks all on its
own after a good warmup period. Serious fumes.
Its been operating this way for some 4 years now. I don't run it all of the
time and I actually recently found what was wrong that always gave it a
slight offset.

So a very good conversation running here with everyone sharing really good
insights and pictures of detail I had only read about and generally without
any pictures. The entire thread should be gathered up, cleaned up, and
presented as the dummys guide to the care and feeding of old 5061s.

Regards
Paul.
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[time-nuts] HP5061B High Ion Current/Tubes Out of Cesium

2017-04-06 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/thread.html

I spoke to Corby on the phone a few days ago about our first HP5061B
that locks fine but has ion current on the order of 76 μA.  It has not
gone down significantly in two months of pump operation.  He mentioned
that the electrodes in the pump are made from titanium and that sharp
whiskers can form on the electrodes from metal migration.  They
apparently cause corona and keep the ion current high indefinitely.
According to Corby, the vacuum in the tube may be fine and the leakage
current make it appear otherwise.

We performed an experiment using our second HP5061B that we suspect of
being out of cesium.  When we first got it, we had about 10 μA of ion
current and within a day it went down to nearly zero.  Today we
jumpered R12 on the cesium oven board to raise the oven temperature.
We previously had checked all waveforms for normal operation on the
board.  This includes measuring cold resistance of the cesium heater
at 2.6 Ω and hot wire ionizer of 0.1 Ω.  Power to each was close to
the nominal 2.6 Watts and 4 Watts respectively.

We bumped oven heater voltage up to 11 Volts with the short on R12.
This could have put up to 48 Watts into the oven heater unless its
resistance went up significantly.  After a couple of minutes the oven
150° C  overtemp circuit shut down the switching regulator.  We saw no
increase of beam current even though normal oven temperature is 85°
according to the tube data plate.  We let the tube cool down and
repeated the experiment several times.  We had turned the beam current
adjust all the way up to -2,880 V.  On our good instrument we can get
20 μA beam current with only -1,700 V or so out of the -2,500 V
supply.  We therefore concluded that the beam tube was hopeless and
decided on the risky experiment.

We removed the +3,500 V supply on the suspected bad tube from the ion
pump and connected the -2,500 V supply to the pump.  We left the
-2,500 supply on the electron multiplier as well.  We saw no drop in
its -2,880 Voltage.  We would easily have seen 200 M Ω worth of
leakage on the ion pump.  Therefore the ion pump will work with either
polarity of voltage.  We have  decided to take the risk of reversing
the diodes on the +3,500 V supply on our good instrument and watch the
ion current.  We hope that the reverse polarity will burn out the
whiskers or other leakage caused by long application of positive
voltage.  We have devised a test that will show up to 1,000 M Ω of any
resistive leakage on the tube before we apply reverse voltage to it.

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] Hot Wire Ionizers

2017-04-05 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html

I posted this patent assigned to Frequency Control Corporation on hot
wire ionizers at http://gonascent.com/papers/hp/hp5061/US3433944.pdf .
They must have been an HP competitor in the 1960s.  It discusses the
physics of cesium ionization and should be of interest

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WB0KVV
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[time-nuts] HP5061B Peak to Valley Ratios

2017-04-04 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html

We did our first Zeeman frequency test on our good cesium 05061-6077
Tube with a 1 Meg scope probe and a 11 Meg Digital Voltmeter in
parallel.  KB7APQ used his digital generator for the variable
frequency.  See paragraph 3-16 on page 3-8.  At 53.53 kc the level
peaked at 3 V peak to peak which is close to the theoretical 1 V rms.
I didn't have a program readily available to do a graph but you can
see the main and upper and lower adjacent peaks. We can compare with
Figure 4-43 (page 4-31) in the service manual for the HP5061B if
anyone can graph this.

We had the C field control at the factory setting of 453.  Our actual
maximum on main peak was 53.657 kc not 53.530 kc.  We got 53.530 kc
with a slightly different new C field setting of 463.  Factor spec is
within 100 cps and we were 127 cps off.  This is probably not a bad
drift for a 30 year old instrument.

https://www.febo.com/pipermail/time-nuts/2017-April/104600.html

kc  beam (C Field set at 453)
55.03  27
54.93  27
54.83  27
54.73  28
54.63  30
54.53  32
54.43  33
54.33  31
54.23  28
54.13  25
54.03  22
53.93  22
53.83  24
53.73  29
53.63  35
53.53  32
53.43  39
53.33  34
53.23  28
53.13  24
53.03  22
52.93  23
52.83  25
52.73  28
52.63 31
52.53 32
52.43  31
52.33  29
52.23  27
52.13  27
52.03  26

We suspect a bad beam tube on our second instrument and therefore
wanted to practice the Low Frequency Coil test on our known good beam
tube.  It allows the performance of the tube to be checked with no rf
drive.  See paragraph 5-175 (page 5-22) We used 26.765 kc and it also
peaked out at 3 V pp.  I discovered that this is half of the Zeeman
frequency but it is not clear why this is so.  We obtained a beam
current of 23 with rf drive removed from the tube by pulling P2 on
A4A1.  I spoke to Corby Dawson last night.  Among many things, he
reported that you will be able to get 80% to 90% of this beam current
in normal lock mode.  We are getting 87% or 20.

πθ°μΩω±√·Γλ
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[time-nuts] Fwd: HP5061B Peak to Valley Ratios

2017-04-04 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html

Here is the plot on the Zeeman frequency data that we gathered this
morning.  It is close to Figure 4-43 (page 4-31) in the service manual
for the HP5061B.  Thanks to Jonathon for plotting this.

http://gonascent.com/papers/hp/hp5061/waveform/zeeman.jpg

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[time-nuts] HP5061B Peak to Valley Ratios

2017-04-03 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-April/104600.html

We hooked up the oscilloscope directly to the electron multiplier in
the beam tube with a 1 Meg termination.  We were operating open loop
and varying the fine crystal oscillator adjust for the different
photos. Remember that higher beam current is downward in the photo.
Currents listed in nA translate to beam current numbers on the HP5061B
meter.

First photo at http://gonascent.com/papers/hp/hp5061/waveform/centered.jpg
is the frequency swept at a 137 cps rate around the peak of the cesium
resonance.  Ground is at the top of the screen and 5 mV (also 5 nA)
per division.  Horizonal is 4 ms per division.This corresponds to a
peak beam current of -22 nA and a valley current of -17 nA.  One
valley current is below resonance and the other is above resonance.
The waveform is 274 cps.  Sequence is low to high and then high to
low.  No 137 cps is present.

The fine frequency control was adjusted to produce a slight offset
from center for the photo at
http://gonascent.com/papers/hp/hp5061/waveform/smalloff.jpg .   Note
that the peak beam current is still -22 nA but two different valley
currents exist.  One is 17 nA and the other is -18 nA.  Most of the
signal is 274 cps but some asymmetry is present at 137 cps.  One
extreme of the sweep is slightly closer to center frequency than the
other.

Finally the frequency was adjusted to produce a severe offset with all
of the sweep below resonance in the photo of
http://gonascent.com/papers/hp/hp5061/waveform/largeoff.jpg .  The
peak is now slightly below resonance at -21 nA and the valley is far
below resonance at 5 nA.  The signal is all 137 cps with no 274 cps.
See figures 4-43 and 4-44 on page 4-31 of the manual for further
explanation.

We will be finding out the effect on beam current of tests shortly on
the Zeeman coil and LF coil.  We think that the 55.53 kc Zeeman
frequency introduces some AM into the beam frequency but no FM.  What
the LF coil has is unclear at this time.

πθ°μΩω±√·Γλ
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[time-nuts] HP5061B Peak to Valley Ratios

2017-04-01 Thread Donald E. Pauly
We are having trouble getting beam current on our #2 HP5061B.  Ion
current has gone down in a week from 10 to zero. It looks like the rf
chain is working normally.  Both HV power supplies had to repaired.
Beam current is all the way up and which gives 2 on the meter. We are
preparing to do the Low Frequency Coil test mentioned on page 5-22
section 5-175.

I got this idea from that procedure.  On our good #1 instrument we set
the beam current at 20 with normal lock.  The middle coax J2 which
carries 12.631 mc to the harmonic generator was removed next.  The
beam current instantly dropped to 2.  We set the beam current with the
front panel control at 10 to 30 and all three settings dropped about
10 to one when the cable was pulled.  This ratio seems to be a good
indicator of beam tube quality.  I don't see it in the manual, but the
fine five turn pot oscillator control works much better than the
course adjustment for setting peak beam current.  It also works better
for setting the control voltage to zero.  The push to turn course
frequency control slot has been chewed up by the previous owner.

We are planning to get an oscilloscope display of the main and
secondary lobes similar to page 4-31 Figure 4-43.  If it works we will
post it.  It should show both the dc and ac parts of the beam current
as the 137 cps sweep goes from one extreme to the other.  Will anyone
having any experience with the Low Frequency Coil test kindly post on
the subject?  This is NOT the Zeeman frequency test.
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[time-nuts] HP5061B Ion Current

2017-03-30 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

I posted another HP cesium beam tube patent at
http://gonascent.com/papers/hp/hp5061/US3387130.pdf .  It covers the
formation of the cesium beam and should be of interest.  We now have
over a month of operation on our first HP5061B at ion currents over 50
μA with no lock problems.  The uon pump voltage is 2,338 V at that
current.

We are still working for lock on our second HP5061B.  Both of the HV
power supplies had to be repaired and other problems remain.  Anyone
having supposedly unusable beam tubes with high ion current should
contact me at trojancowboy at gmail .com.



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WB0KVV
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[time-nuts] HP5061B Cesium Oven Properties

2017-03-29 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

The cesium oven acts as an evaporator for liquid cesium which melts at
28.5° C.  One of our beam tubes has 83°C for its operating
temperature.  It also calls for a A11R11 and A11R12 of 3.83 K and
42.2K which is 3.51K.  Oven power is specified at 2.2V and 0.9A or
1.98 W.  Being in a vacuum allows less heater power.  Oven temperature
is very critical to provide enough cesium in the beam but at the same
time not wasting it.  A switching power supply runs the oven as well
as providing 1.2V at 3.4A to the hot wire ionizer which is 4.08 Watts.

It took 10 minutes from a cold start for the cesium oven current to
drop from being pegged to its final value.  After stabilizing, we
connected a 470 Ω across the thermistor from the beam tube to shut off
the heater.  Here is the beam current versus time in minutes as the
oven cooled off.  Note that it took 17 minutes for the beam current to
drop to half value.  Continuous lock was maintained.

time beam
0 20
3 18
5 17
8 16
9 15
1114
1412
1711

We then reapplied oven power and watched the beam current increase and
oven current decrease.

time beam oven
0  16 over 50
3   20missed
5   22missed
6   2115
8   20 15
10 20 14

Finally we applied oven power from a 35 minute cooldown and waited for
lock.  If the oscillator oven is stable, the cesium oven will achieve
lock in only two minutes.  There is no need to waste cesium if you do
not need the instrument to be locked.

time beam status
0  8   unlock
2  10 lock
3   12lock
4   18lock

πθ°μΩω±√·Γλ
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[time-nuts] Fwd: HP5061B Ion Current

2017-03-28 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

We continue troubleshooting our 2nd HP5061 acquisition.  The 200 Meg
resistor in the +3,500 V supply had gone way up in value and made it
appear that the supply was half normal voltage.  See the black
resistor in http://gonascent.com/papers/hp/hp5061/3500top.jpg .  We
installed a temporary resistor.  The ion current was pegged when we
reinstalled the supply.  This is not surprising since instrument has
been stored for over a year.

Here is the way that KB7APQ unsoldered the latest two high voltage
supplies. See  http://gonascent.com/papers/hp/hp5061/desolder.jpg .

High Voltage Power Supply Unsoldering and Repair
1 - Suspend power supply on steel wires using 6-32 ground lugs and nuts.
2 - Heat solder joint evenly all the way around using a propane torch.
Be careful to avoid too much heat on connections. Act as quickly as
possible to avoid overheating components.
3 - Pull down firmly on outer can while wearing a welding glove.
Rotate unit until can comes away from power supply. Cold solder on the
inside of the can can prevent power supply from sliding all the way
out. You may want to shake off some excess solder as it melts.
4 - When can slides off of the power supply turn it over and tap it on
the floor to remove excess solder from the inside of the can.
5 - Mark can for mounting holes to be used to reattach outer can after
repair. I used 0.970 inches from the can side and 0.100 inches from
the open end. The off center 0.970 dimension is to avoid power supply
screws from interfering with each other in the event both power
supplies need this modification.
6 - Center punch where marked then insert power supply back into can.
Note the orientation for the label on top. Using a number 50 drill
bit, drill through both can and base.
7 - Tap holes in the base using a number 2-56 tap.
8 - Enlarge the holes in the outer can using a number 43 drill bit.
9 - Use 2-56 x 1/8" pan head screws to secure the outer can.

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] Fwd: Fwd: HP5061B Ion Current

2017-03-27 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

The -2500 supply is nearly identical to the +3500 supply.  We will
post some photos on the disassembly process.  We also had to
disassemble the +3,500 supply because the 200 Meg resistor had gone up
in value.   It showed only 1,900 V with no load when it should have
shown 3,200 V.  We replaced the 47 uFd electrolytic with a tantalum as
a preventive measure.

After we repaired the -2,500 supply we measured the output voltage
versus beam current as set by front panel adjustment. Note that about
a 10% increase in electron multiplier voltage will double beam
current.

beam current  High Voltage
30 -1,755
20 -1,658
10 -1,507

On our freshly repaired HP5061B, we ran it four hours with no voltage
on the ion pump.  It maintained lock when voltage was reapplied.  Ion
current and voltage were unchanged at 76 uA and 2500 V.  You
apparently can operate for some time with no ion pump.

Really good pix on the inside of the 3500V module. So the opening of the
can is the typical lots of heat and pry it open approach right?
How about a good pix of the 2500 Volt module?
Thanks
Paul
WB8TSL
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[time-nuts] Fwd: HP5061B Ion Current

2017-03-26 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

We continue to try to achieve lock on our latest HP5061B acquisition.
We found that the -2,500 supply would only come up to -780 V under
normal 55 Meg multiplier load.  When we pulled off the HV lead to the
beam tube, it came up to only about -1,500V.  After another horrible
desoldering job, Q2 collector waveforms were essentially normal.  We
found a near open C1 which is 47 μFd at 35 Volt electrolytic was open.
This caused massive spikes on the bypassed +18.7 line.  We replaced it
with a tantalum.  This brought it up to normal -2,700 V for full
clockwise beam adjust on R7.

Next we found that the +3,500 supply was only up to 1,000 V with
normal ion current load.  We expect to find the same problem on this
supply.  See http://gonascent.com/papers/hp/3500top.jpg.  C1 cannot be
seen in this photo.  Ion current was only 15 μA because of the low
supply voltage.  I will have another post on what we found about
electron multiplier voltages.

DEP

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] Fwd: HP5061B Ion Current

2017-03-24 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

The design on the voltage and current limiter is complete but not
breadboarded yet. We are getting a little more time on our HP5061B
beam tube after beefing up the +3,500 Volt power supply.   We have the
frequency control R4 turned all the way up to 1900 cps with beam tube
ion pump load.  We have a shunt across the ammeter so it can measure
100 μA full scale instead of 50μA.  We dare not disconnect the load
because voltage limiting is not operational yet.  Continuous lock
light is lit.  Note that lock is normal at over 3 times what the book
said was normal cesium turn on point.  If we could go to +3,500 Volts,
the current would likely be 100 μA.  I calculate that lock would be
normal at 1 mA ion pump current.

time   μA voltage
08:46 56  3,620
09:46 70  3,400
11:25 72  3,360
12:58 76  3,300

We just got in our second HP5061B yesterday  It's ion current was only
14 μA but we haven't checked the voltage on the +3,500 V supply yet.
It appears to have a problem with the -2,500 V supply.

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] HP5061B Ion Current

2017-03-23 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

The patent that I posted at
http://gonascent.com/papers/hp/US3323008.pdf has many interesting
facts about the cesium beam tube.  It says that the temperature of the
cesium oven is 65° C.  I researched the vapor pressure of cesium at
various temperatures.  With a change of 30° C in the oven temperature,
the cesium pressure goes up or down by 10 to 1.  If the oven
temperature goes up by 5°C, cesium use rate goes up by 1.46 to 1.  If
it goes down by 5°C, cesium consumption decreases by 1.46 to 1.
Cesium oven temperature is quite critical to beam tube life.  The
HP5061A has a switch to reduce cesium oven temperature to increase
beam tube life at a price of slightly worse short term stability.

If the oven is shut off in CS OFF mode, pressure drops to 1.41x10^-6
Torr at 25 at temperatures about 25° C.  This is 2.8 times more that
the 5x10^-7 Torr that is considered a good vacuum for the tube.  good
vaccum is considered 2 μA on the ion pump. This would be 5.6 μA for
the higher pressure.  Therefore, the tube will get somewhat gassy if
the instrument is not used.  If it is stored at temperatures about 25°
C while not in operation, the situation is worse.  I don't know what
is causing higher currents but it must be contaminants beside cesium.

http://www.powerstream.com/vapor-pressure.htm

C°  log mm Hg
-18° -8
2° -7
22° -6
47° -5
77 -4
109° -3
155° -2
207° -1
252° -0

πθ°μΩω±√·Γλ
WB0KVV
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[time-nuts] Fwd: Fwd: HP5061B Ion Current

2017-03-22 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

I have posted two HP patents on the cesium beam tube at
http://gonascent.com/papers/hp/US3323008.pdf and
http://gonascent.com/papers/hp/US3397310.pdf . Both are of academic
interest. The first claims that the cesium oven operates at 60°-70° C.
This is a tiny heating compared to a 1,000° filament on a power
transmitting tube.  I say that it can be cycled a million times with
no problem of thermal cracking.

πθ°μΩω±√·Γλ
WB0KVV

-- Forwarded message --
From: John Miles 
Date: Tue, Mar 21, 2017 at 5:41 PM
Subject: Re: [time-nuts] Fwd:  HP5061B Ion Current
To: Discussion of precise time and frequency measurement
, rwa...@aol.com

That's some very nice work, Donald.  Looking back, I have junked one
or two Cs tubes that might have been usable if I'd thought through the
problem of high ion pump current as you and KB7APQ seem to have done.

Another good reason to raise the lockout threshold would be to cut
down on the repetitive ionizer filament cycling that the tube will
otherwise undergo when you first fire up the oven.  That phenomenon
always makes me rally nervous.

-- john, KE5FX
Miles Design LLC

> -snip-
> When we overrode the cesium lockout at 29 μA or so of ion current, we
> needed only minor front panel adjustments for beam current of 20 μA.
> (We shorted across A15 R-4.) Our last ion current before power supply
> modifications at risen to 39 uA.  Beam current has been stable.
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[time-nuts] Fwd: HP5061B Ion Current

2017-03-21 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

You bring up an interesting point.  As the cesium is used up over the
years, it forms a cesium frost which deposits on everything inside the
tube.  If it gets thick enough it conducts or can arc between frost
grains.  A charged capacitor can blow some of this away.  Cesium melts
at 83° F.  If you heated the beam tube up in a hot car or out in the
hot sun, you could turn this frost into dew.  The dew might run down
hill into some cesium lakes where it was harmless.  Those lakes would
freeze when back at room temperature and might be even more harmless.

I have seen two TV picture tubes that developed leakage between focus
and screen electrodes.  Adjusting focus changed the brightness and
adjusting the screen changed the focus.  I applied the high voltage
between the two and the arc burnt out the high resistance leak.  It
saved both picture tubes.

WB0KVV

πθ°μΩω±√·Γλ

If you cannot get the ion current below 50ua or so after a week at 5kV
then you are out of luck. Most likely you have resistive deposits on
the ion pump insulator. If you can get the tube to give a decent SN at
those levels then you can
run with the alarm circuit bypassed.

I have run tubes a couple years this way (at <50ua) but if you let them
sit cold you will have to manually cycle the ovens at turn on until the
excess gas load is pumped. If you have a bad ion pump supply when you
open it up to repair it I would suggest adding a 66K resistor across
the 75K resistor. This will increase the alarm trip up to about
40-45ua. If it's the older one the oil capacitors will need changing
as well as the 200Meg resistor.

If the later one (in the 5061B) then the 47uf radial cap is open. both
these units are interchangeable. One other trick is to use a spark
discharge tester (miniature hand held tesla coil used in the neon sign
industry) to ZAP the ion pump lead. This can blow out any whiskers
that the ion pump has developed. You can
also (carefully) with the HV on, remove and replace the ion pump
connector a few times. Sometimes you will get a sharp discharge that
blows out the whisker. I have used both methods with good success.

Cheers,

Corby

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[time-nuts] HP5061B Ion Current

2017-03-21 Thread Donald E. Pauly
It looks like that there is about 10% hysteresis on the cesium trip
off/on. That may not be enough to prevent cycling on and off.   I may
not have made it clear but instability in the +3,500 voltage makes a
big difference in the threshold ion current required for activation.
If it fades it can require a 10 uA smaller ion current to activate
cesium.

-- Forwarded message --
From: John Miles 
Date: Tue, Mar 21, 2017 at 5:41 PM
Subject: Re: [time-nuts] Fwd:  HP5061B Ion Current
To: Discussion of precise time and frequency measurement
, rwa...@aol.com


That's some very nice work, Donald.  Looking back, I have junked one
or two Cs tubes that might have been usable if I'd thought through the
problem of high ion pump current as you and KB7APQ seem to have done.

Another good reason to raise the lockout threshold would be to cut
down on the repetitive ionizer filament cycling that the tube will
otherwise undergo when you first fire up the oven.  That phenomenon
always makes me rally nervous.

-- john, KE5FX
Miles Design LLC

> -snip-
> When we overrode the cesium lockout at 29 μA or so of ion current, we
> needed only minor front panel adjustments for beam current of 20 μA.
> (We shorted across A15 R-4.) Our last ion current before power supply
> modifications at risen to 39 uA.  Beam current has been stable.
>
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[time-nuts] Fwd: HP5061B Ion Current

2017-03-21 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

Paul:

I don't think that I made myself clear.  This power supply is a rare
example of HP engineering incompetence.  The transformer is EASILY
capable of 10 Watts out at 3500 V.  Instead they made it where it
can't even put out 100 mW without sagging.  This supply was designed
in the middle 80s when IC technology was well developed.

>From what I am able to determine about ion pumps, current is
proportional to pressure and voltage is proportional to pumping rate.
Paragraph 4-349 of the HP5061B manual states that 2 μA ion current
corresponds to a pressure of 5x10^-7 Torr.  At 760 Torr, the mean free
path of an oxygen molecule is 93 nm.  Assuming that a cesium atom is
the same size, this gives it a mean free path of 141 meters.  This
means that there is a 50% chance of a collision in a 141 meter travel
thru such a vacuum.  At an ion current of 1 mA, the pressure would be
500 times greater and the mean free path 500 times less or 0.282
meters.  This is 11" or about the length of travel for the beam in the
tube. A beam current of 1 mA would only cause a loss of 50% in beam
current and should still allow lock.

That same paragraph claims that cesium is turned on at 40 μA.  That
was not true.  Another place claims 20 μA (Appendix A-1 b) as well as
30 to 40 μA.  The exact trip point depends on how much sag occurs in
the HV supply and is very complex to calculate.  It is stupid to have
to wait for weeks for a reduction in ion current to allow the cesium
to come on naturally.  Lock can be achieved instantly.   I think the
final vacuum improvement can be achieved more quickly if the cesium
oven is on.  It should cook off cesium that has condensed on its
outside.

See page 8-51 schematic.  We measured the properties of the power
supply as it is.  For 18.7 V supply, 357 μH and 20 μs, energy stored
is in T1 primary is 108 μ Joules.  Frequency can be adjusted from 524
to 2002 cps.  Power supply with no load was set to 704 cps for +3,500V
out with no load except for the internal 200 Meg bleeder.  Input power
was 76.3 mW and output power was 61.25 mW or 80% efficiency.  At
frequencies above 704 cps, output voltage increases above safe levels
for no load.

With gassy beam tube for load, voltage sags to 2296 V with 39 μA ion
current 11.4 μA bleeder current.  Total power is 115.9 mW.  With
frequency raised to 55 μA ion current, voltage was 2460 V or 165 mW
power.  With frequency turned all the way up to 2002 cps, voltage was
2562 V and 71.4 uA ion current or 215 mW power.

We are working on a voltage regulator and current limiter that will
provide at least 1 mA before voltage reduction from +3500V.  This is
an improvement of at least 20 to 1. Output power is limited by the 21
kc self resonance of the transformer due to secondary winding
capacitance.  We don't know its saturation current yet. We plan to use
the two unused meter switch positions to monitor output voltage and
current.  It will likely mean that no external 3500 volt supply will
ever be required for tubes that have been in long storage.

I made a typo on WB4BPP's call in my first post but he reports using a
5,000V external supply.  He didn't provide current figures or whether
this voltage actually stayed there.  I am concerned about arc over at
the ion pump at that voltage.  Ion pump manufacturers caution about
overheating at high pump currents.  HP claims in Appendix B A-2 h that
+3500 V at 5 mA for no more than 15 minutes is permissible.  This is
17.5 Watts which sounds like a lot for a small cathode.

When we overrode the cesium lockout at 29 μA or so of ion current, we
needed only minor front panel adjustments for beam current of 20 μA.
(We shorted across A15 R-4.) Our last ion current before power supply
modifications at risen to 39 uA.  Beam current has been stable.

WB0KVV

πθ°μΩω±√·Γλ

-- Forwarded message --
From: paul swed 
Date: Mon, Mar 20, 2017 at 7:08 PM
Subject: Re: [time-nuts] HP5061B Ion Current
To: Discussion of precise time and frequency measurement 

Donald welcome to the group. If a units been off a long time and it sure
sounds like thats the case it may take quite a while like a month or so for
the unit to remove all of the "Stuff" that has out gassed. So be patient
and let the pump do its job. After it does lower and my fingers are
crossed. Then you only need to run it about every 6 months.
The fact that it actually locks and you found a simple fix is pretty good.
What was the beam current?? That gives you a hint on the quality of the
tube.

Not sure I would run the defeat on the HV supply for to long. That may
stress the supply if I had to guess.
Regards
Paul
WB8TSL
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Re: [time-nuts] HP5061B Ion Current

2017-03-20 Thread Donald E. Pauly
https://www.febo.com/pipermail/time-nuts/2017-March/104374.html

I could not figure out why the A15 Ion Current monitor would not let
the cesium oven turn on with ion current under 25 uA.  At the time we
had no way of measuring the +3,500 ion pump supply.  We bought some
200 Meg resistors and made a crude HV meter to feed our 10 Meg Fluke
77.  The supply had sagged to 2000 Volts with that load.  This
prevented the ion pump current monitor from energizing the cesium
oven.

KB7APQ unsoldered the can on the 3,500 Volt supply with suggestions
from WB4BBP.  It is a horrible design and we studied it.  R4 is set at
the factory to produce 3,500 Volts with no load.  It runs at 704
pulses per second and sags badly with the slightest load.  This
prevents the ion pump from clearing the gas in the beam tube.  The pot
core transformer is plenty big that it appears that the supply can put
out 5 mA at 3,500 volts.  This allows it to replace the external
supply recommended by HP for gassy tubes.

It looks like that it can run at 10 kc with existing pot core
transformer.  The pulse width looks like it can be doubled as well.
This allows for a 30 to 1 increase in output power.  A small circuit
board will regulate the voltage as well as limit the current.
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[time-nuts] HP5061B Ion Current

2017-03-20 Thread Donald E. Pauly
This is my first post.  I just bought a non-working HP5061B on eBay
for $350.  My old boss KB7APQ in Salt Lake City and I are working on
it.  It came in from the Philipines in October of 2015 and was
diagnosed with a bad physics package in March 2016 by AllTest in New
Jersey.  We initially found an open R8 pot on the 5 mc oscillator
A10A2 which was killing most of the output.

Next we had ion current of about 25 uA which stayed up.  The book
seems to indicate that this was low enough to enable the cesium oven.
The analysis of the theoretical ion current for cesium turn on was
very difficult.  We shorted the base emitter of Q6 on A15 board to
override Cesium oven disable. The instrument then achieved lock with
beam current of 20.  Ion current rose to 35 after cesium oven warm up
and lock.

We have made great progress on the +3500V power supply analysis.  We
believe that many so called gassy tubes are perfectly functional up to
1 mA ion current.  Mean free path is on the order of 142 mm in that
case or the length of the beam.  We will discuss our findings if there
is interest.

WB4BBP has been most helpful with our efforts.
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