Cesium Frequency Std
Datum 4065B Time & Frequency Standard
Fast Test Method with
4065B Frequency Offset
Symmetricom Chip Scale Atomic Clock
|Datum 4065B Cesium Time
& Frequency Standard top off showing three 8 Volt
On the right the toggle switch (advance/retard and the
7 thumbwheel switches control the movable 1 PPS output
in 100 ns steps.
The BNC just below the toggle is the programmable
frequency TTL square wave output (.1/1/5/10 MHz).
The yellow cap is on the 1 PPS master output.
The black cap is on the 1 PPS sync input BNC.
4065B Rear Panel
Two 7AH Gel Cell 12 Volt Batteries connected while
working on the three 8V 5 AH batteries.
Just to the right of the line cord jack is a toggle
switch which when turned down shuts down all of the
unit except for the ion pump.
A much better solution to storage than circuit mods.
The field of type-N connectors has 3 ea 10 MHz out, 3
ea 5 MHz out and 3 ea 1 MHz out all 1 Vrms, 50 Ohms.
The BNC above the DB-9 is the alarm status and the
DB-9 is alarm info.
The DB-25 is a serial connector for data I/O.
This box does not have the optional telecom outputs.
The far top right BNC is the master pulse out.
Below it is the adjustable offset 1 PPS out.
|Getting ready to
compare them. You can see the family
resemblance. Note both units are locked and
The 4060 is s/n 1227 and should be fairly close to on
Fast High Precision Set-up of SR
This idea is from the PRS10
Rubidium Frequency standard manual appendix B.
- 10 MHz Reference to BNC-T on rear panel 10 MHz Input
then to front panel "A" start input
- 10 MHz DUT to front panel "B" stop input
- Front panel 1 kHz TTL REF OUT to front panel EXT
- CONFIG - press SET to select cAL and press
SELECT to choose "cLoc SourcE", use arrow keys to set
- in the Gate field: select POS, TERM = 50 Ohms and
LEVEL= +1.0 Volts
- for sine wave 10 MHz inputs set the A and B input
fields to: AC, 50 Ohms, Level full CCW, + Slope.
MODE to FREQ, SOURCE to B, GATE/ARM to 1 second and SAMPLE
SIZE to 1 then hold START down for a few seconds, DISPLAY
This display should be within 0.1 Hz of 10 MHz
Fine Frequency Measurement
This will show 1E12 in one second.
MODE to TIME
SOURCE of Start to A
GATE/ARM to +TIME and EXT
SAMPLE SIZE to 1000 (1 & 103
Now each second there will be a display of 1,000 averaged
readings. This brings the 620 precision down to 1
Datum 4065B Cesium Time & Frequency
The FTS4060/S24 is really a frequency standard and I've always
wanted an excellent time standard.
This unit came from an eBay ad showing a Major alarm and not
locked. But when powered up it locked in about 10
minutes and after connecting the removed and taped battery
wire and waiting an additional 10 minutes the charge fault
could be cleared.
Each of the three batteries is has four "X" 5 AH cells where
each cell is a Cyclon cylindrical sealed lead acid
cell. The 2.5 AH "D" cells were used in the O-1814
Rubidium Time & Frequency
standard. The top of each battery is marked "bad" and a
date of 10-2-01. The voltage across the pack is now 31.2
VDC but there probably is no current flowing if any one cell
is bad, so some testing will be needed to see what the real
Theory of Operation
This is a modern Cesium standard that uses control loops so
that it's frequency is correct, i.e. the C-field adjustment is
automatic not manual like the 4060.
Unlike the FTS 4060 where you manually set the C-Field this
one monitors and adjusts based on the following items as
reported in the Status 5 menu:
-10 S.B. <= 160 mv
0 S.B. <= 40 mv
-15 S.B. <= 160 mv
Rabi-Zeeman Error -4
S.B. <= 160 mv
Ramsey Confidence +3
S.B. <= 160 mv
The AC mains power a 31 VDC supply that's diode ORed with the
internal battery and the external DC supply. The
internal supply is a 24 Volt lead acid battery, 12 cells of
Cyclon "X" size cylindrical sealed pure lead acid. There
are a couple of major problems with this:
- The temperature inside the case is always warm to almost
hot. That degrades the life of the lead acid battery
by an order of magnitude.
- If there's any venting, like happened with the Gibbs
double oven crystal oscillator, the fumes and heat make a
good combination to etch the traces right off printed
So, rather than replacing the internal lead acid battery, it
will be connected as an external battery. Since a diode
OR gate is used to combine the three power supplies a new wire
needs to be run to one of the unused pins on the external
battery connector to bring out the internal battery terminals
to allow float charging.
The Red-Black Siamese cable has male 1/4" Faston connectors
that match those on the batteries and so plug into the
internal battery wiring connectors. The white label
Remote Internal Battery D:
-24, E: +24 VDC
The Plug in the lower right of the photo connects D to black
and E to Red. The other end of the cable has female 1/4"
Faston connectors to plug into the battery. This solves
the two major objections to an internal battery, i.e:
- If battery vents acid fumes they will
not destroy the expensive circuitry
- The battery will last 3 to 10 times
longer when running at room temperature
Pins D and E on J100 External DC Input were spares and so a
true external battery can be added just be wiring it to pins A
(positive) and C (return). Note the external
battery must have it's own charging circuit and should be at
some voltage level chosen by what priority it should be used.
4065B Frequency Offset
On the FTS4065 the C-Field adjustment is made by the internal
microprocessor and there is a seperate Frequency Offset
After plotting for the time interval between the 4065B and GPS
from 5 May to 7 May (4065plot9.pdf
and finding a straight line with a slope of 472E-15 the
Frequency Offset was changed from +000000 to +000472 (a 50-50
gamble that the sign should be +).
A new plot was started 7 May after the change and for the
first couple of days seemed to have worked. By starting
a new plot I mean that constants were subtracted from the time
interval so it starts at 0.0 and the starting second count
starts at 0.0. This way is the plot is a straight line
it can be forced to go through (0,0).
By May 10 at 9:50 am it looked like the frequency offset had
worked. The data (plot10a.pdf
a box about +/- 10 ns high after 2 3/4 days (3E-13) but more
time needed for good data.
Then the points started a climb. By 14 May (4 days
later) the data between May 10 and 14 looks again like a nice
straight line (plot10.pdf)with a slope of about 472E-15.
BUT the frequency offset is still set at +000472.
The 4E-13 number floating on the plot is the slope after one
day. Just put it there so I could remember what it
was. Excel recomputes the slope as each new data point
The 4065 box was rotated 90 degrees and it did make a good
Before this plot was started the frequency offset was stable
at 472 (parts in E-15) and the 4065 Frequency Offset was set
For the first couple of days it looked like that change was
working and the frequency offset was near zero.
But then the frequency offset returned to +472 (this with the
Frequency Offset dialed to 472) and that continued for over
four days when I turned the 4065 box 90 degrees clockwise
(just prior to the day 7 grid line). That made a big
change and now (May 17 2008) the slope is more like 167 (parts
It may be that the Earth's magnetic field is having an
influence or maybe just the mechanical shock has the
Any thoughts what's going on? Contact
Model Numbers & Options
Setting C Field
Manual Control Voltage & Loop Gain
Government Liquidation Warning
A common misconception (and one
that I had until working with a Cesium standard) is that the
timing is perfect. This is not the case. A Cesium
standard wanders around the nominal frequency, but may not
drift like a crystal oscillator. A couple of terms will
help when working with this concept.
Offset - is a measure
of how close to the desired frequency an oscillator is
running. For example an oscillator that's supposed to be
at exactly 10 MHz is off by 0.0001 Hz has an offset of
1E-11. The offset is only valid at the instant when it
was measured. It's measure a of how well someone set the
frequency not so much about oscillator quality. Since
this is something that's under the user's control a lot of
time and effort go into minimizing the offset. It's
common practice when setting the frequency of a lab grade
crystal oscillator to set it right at the edge of the system
spec, but on the side where aging will move the frequency so
it at first gets better, then it's perfect, then it moves to
the other side of the spec. In order to do this the
aging rate (i.e. stability) needs to be known.
Note that a Cesium standard may not be set to have a zero
offset, but rather most end up with an offset on the order of
parts in E13 or E14. The offset is known and can be
backed out of measurements on other time standards. But
if the Cesium standard will be driving a clock or say a
transmitter, the setting the offset to the lowest possible
value is important. The key thing is that there is no
aging, i.e. a time interval plot vs. GPS will be a straight
line whereas a crystal or Rubidium oscillator will have a
Stability - Stability
is the money spec. a measure of how well the frequency stays
the same. A perfect oscillator would not change
frequency with time, power input, temperature, etc., but you
can't get that one. The measure of how the frequency
changes with running time is called aging. The
specification on the HP (Agilent) 5071A Cesium standard ($50k)
is less than 1E-14 per day. . That's to say that
if it was set with a zero offset at noon today, by tomorrow
noon it might by off frequency by 1E-14.
The plot at the bottom of web page
http://www.niceties.com/utcdwh.html (650 days of data) shows
what might be a random walk of around plus and minus 100 ns
for an HP 5071A.
My s/n 1227 is running at abut -1.4E-14 per day. It
would be a tad out of spec for the HP 5071A. Cesium
sources are NOT supposed to have aging ike this.
Cesium standards are a step
better than Rubidium standards and are the basis of the
definition of a second. But that does not mean they are
These are the S24 option that has a 1 MHz front panel output,
NSN 6625-01-245-3092. The official definition of a
second of time is exactly 9,192,631,770 oscillations of a
Cesium atom between the F3 and F4 states.
was probably the first commercial Cesium
standard. It was all analog, no microcontrollers
then. HP took over the Varian line of Cesium
standards. Then when HP and Agilent split, Agilent
kept the Time and Frequency instruments and HP then became a
computer and imaging company.
The FTS4060 I would call a
second generation Cesium standard because it has a micro
processor that replaces a lot of analog circuitry and is
much easier to use. There is a manual C field
adjustment that needs to be set where the coarse thumb wheel
is 1E-12 per tick and the fine wheel is maybe 1E-14 per
These were purchased from Government Liquidation with a
condition code of "A1" which should mean that they are
new. Here are some dates:
date on Lid
Possible meaning: The first
control voltage measurement was done at the factory as part of
the final inspection and so is close to the ship date.
These dates and the serial numbers are in the same
order. The front panel date may be when the units were
tested prior to being put up for auction. These dates
seem to be over 2 years prior to the auction date which may be
due to how fast the government surpluses them. Note that
it's about 14 years from the final test date to the surplus
date. So maybe there is some number of storage years
after which these units are surplused, say 15 years.
s/n 1013 was shipped outside it's carton and failed to lock
when received. Opening the bottom of s/n 1013 shows the
Cesium Beam tube, Brick power supply, and fancy 10 MHz crystal
oscillator plus other components. Behind the Cs tube is
paper work indicating it was replaced in 1996. There
must be some reason that s/n 1013 is not working, need a
manual to find it. In the left photo at the top of this
page notice that the green "LOCK" light is on for the top two
standards (1033 & 1227) and off on the bottom (1013) one.
Model Numbers & Options
The normal FTS4060 comes in with
either a 10 MHz optimized output (/201) or a 5 MHz optimized
The /S24 option was a special unit made for the U.S. military
and has only a 1 Mhz output on the front and rear panels and
does not have other frequencies as outputs and does not have
the 1 PPS output. It does not have the internal or external DC
supply options. It's a stripped down model.
All of my units (s/n 1013, 1033, 1227 have the SMA-f connector
on the A5 Distribution Amplifier Assembly, but not all /S24
units have this connector. It's the 10 MHz output at
about 4.4 V Pk-Pk.
My s/n 1013 has a rear panel with a number of plugs like it
was the same rear panel used for a full featured 4060, but s/n
1227 has a solid rear panel with no plugs, so in order to
install the 10 MHz port I moved the alarm connector to the
inside of the box and replaced it with the 10 MHz output.
Note that some FTS 4060 use a 5 MHz OCXO and others use a 10
061 - 1 MHz and 100 kHz RF outputs
116 - Time-of-Day Display and 1 PPS Advance/Delay
117 - 1 PPS Advance/Delay
010 - Internal Battery and Charger
015 - External Standby Battery Supply
013 - Chassis Rack Slides
Just plug in the line cord, set
the Mod switch to ON and the LOOP switch to CLOSED.
After something like 10 minutes to 30 minutes the green LOCK
light will turn on and the ALIGN pushbutton-lamp will turn
You can manually press the Red Operation Alarm Light/Switch to
turn it off.
Pressing the AC Power Reset switch will turn off the red Alarm
Pressing the Align Light/Switch may turn it off or initiate a
new align sequence.
The Voltages shown on the meter have been scaled to fit the
meter's 0 to 5 volt range and are not the actual voltages in
Near the brick power supply on the top side there's a Molex
type connector with Red, Black and Orange wires. The
connector is the same 4 terminal connector as used for hard
drives in PC computers. To get a mating connector buy a
"Y" PC power supply cable. You can tease out the male
pins using a jeweler's screwdriver if you don't have the
extraction tool ( a hollow tube that fits over the male
pin). The reassemble with the black wire going to the
black ground wire in the FTS4060, Red to the +30 wire and
yellow going to the orange +5 volt wire. This makes for
an easy way to connect both an external DC backup supply, like
the Austron 1290A and also to supply 5 volts for a 1 PPS
Setting C Field
23 May 2006
Until about a week
ago I was using the GPS 1 PPS as the start pulse
and the 1 Mhz output from the FTS4060 as the
stop pulse into a Stanford Research SR620 Time
Interval Counter and doing 500 second
averages. There are some problems with
- The 1 MHz signal only allows a TI range of
1 micro second before rollover occurs.
- When you get near the rollover the average
value includes data from both sides of
rollover and is very wrong
- MOST IMPORTANT the noise is much higher
than it needs to be!
By changing the setup so that the FTS4060 10 MHz
output feeds the SR620 rear panel Reference
Input (and setting the counter to use the
external reference frequency) and then using the
front panel 1 kHz Reference output as the stop
signal two things happen. The rollover
time is now 1 milli second (10,000 times longer)
and the noise is reduced (probably SQRT(10000) =
100) by a huge amount.
With a 1 MHz stop if the TI is between 0 and 200
or between 800 and 1000 there is a chance of
rollover points being in the average and between
0 and 100 or between 900 and 1000 it's almost
certain that there will be rollover points in
the average. Because of this I'm currently
slewing s/n 1003 which was at 980 ns and may
have an optimum C-field setting of 908 by
setting the C-field at 000 where the slew rate
may be in the +20 to +40 ps/sec area so it sill
take many hours to get the TI to about 500 ns.
Note that the 1
kHz out and the cable between Ref Out and B
in, have an associated time delay so the TI
numbers will not match those with a direct
17 May 2006 s/n
By plotting the offset vs. C-field switch setting
it's clear that the slope is -1E-13 per tick.
This is also a great way to see which data points
are not valid. For example the old data point
for C-field setting 492 was +9.8E-13 which is maybe
10 times higher than where it may end up. As
of 22 May 2006 it's -6.24E-14 with R2 of 0.84.
When R2 gets up to one or two nines, then we'll see.
Note that a Cs frequency
source is just like any other high stability source and
needs to have it's frequency set. The big advantage of
Cs is that once set it will not drift like Rb or
Quartz. Note this is because of the defination of
time, and maybe is not reality.
15 Feb 2005 - The time interval plot was drifting up so an
adjustment was made to the C field. It turns out that
the adjustment was too large. 24 hours after the
adjustment for abut 6 hours the time interval stayed
constant within about 10 nano seconds. This indicates
that even 24 hours after a C field change the frequency has
not stabilized. It really does take two to three
days for the unit to stablize after a C-field change.
Slew using C Field
9 March 2006 - When using a time interval counter where the
start signal is the 1 PPS output from a GPS timing receiver
and the stop signal is from the 1 MHz output of the FRS4060
the counter has a range of 0 to 1,000 nanoseconds. If
the time interval rolls over you get a saw tooth type
plot. In order to slew the time interval away from 0
or 1,000 you can set the C field as far as possible from the
correct setting. For example on s/n1013 the correct
setting will be near 855, so setting to 000 causes the
frequency to slew at about 1,400 ns per day which is
an offset of 1.6E-11 but you can see to get a 500 ns change
will take about 8.5 hours. Not as fast as you would
like. There may be other ways to slew, but so far this
Note that when the C field is misadjusted as much as
possible (1.6E-11) the offset is 10 to 100 times better than
the best ovenized lab grade crystal oscillators daily aging
rate(1E-9 to 1E-10).
Thumb Wheel Switch Sensitivity
11 Dec 2005 - s/n 1013 after complete disassembly and
reassembly seems to be working, not like in Jan 2005.
With C field thumb wheel switches set for 500 the plot of
(start = GPS 1 PPS, stop= FTS4060 1 MHz zero crossing) has a
positive slope of about 5.7864 ps/sec and the plot with C
field at 900 has a slope of -1.7764 ps/sec. So the
thumb-wheel switches may have a scale factor of:
Scale Factor = (7.5628 - (-1.7764)) / (900 - 500) = 0.023348
ps/sec or about 2E-14 per click.
See framed coment above the scale factor for s/n 1227 is
-1E-13 per tick.
When making a Time Interval
measurement there are different signals that can be
used. The common ones are a 1 PPS, 1 MHz or 10
MHz. The big advantage of the 1 PPS signal is that
it takes a long time for a 1 second rollover. If the
TI counter is triggered with a 1 PPS pulse (like from the
PSR10 Rb source) and the 1 MHz output from the /S24 Cs
source is used as the stop signal to the SR620 then the
data will have a range of 0 to 1 micro second. (i.e. the
period of the 1 MHz signal). If the Cs source can be
off by as much as 1000 counts where each count is 1E-13
then it might be off by as much as 1E-10. When the 1
MHz output is used as the stop signal then rollover might
occur every 1000 seconds. This means that the TI
needs to be measured a number of times inside each 1000
second period. You can not just measure at times
seperated by 24 hours when the source stability might be
as bad as 1E-10.
If a 1 PPS stop signal was available from the Cs source
then there would be no rollover problem since a source
with 1E-10 stability will only drift 8.6 micro seconds in
I have a WWV clock and when the 1 PPS from the PRS10 is
used to trigger the A counter input the counter trigger
LED is flashing at exactly (as seen by eye) that same time
as the WWV clock changes seconds. This makes it easy
to tell which reading is axactly on the minute for manual
recoring into an Excell spreadsheet.
If the 1 PPS output from a
Motorola M12+T Timing receiver had the sawtooth
corrected so that it was not modulating the 1 PPS
position then the time needed to set a Cs standard would
be reduced by a factor of 10 or more. For example
if instead of an uncertatiny of +/- 50 ns on each pulse
the uncertanity was +/- 1 ns then instead of needing
50,000 seconds (13.8 hours) to see 1E-12 you would only
need 1,000 seconds (16.6 minutes)
WRONG #1- Since
the saw tooth error is symetrical it gets removed when
averaging is done. On a 500 second average using
the GPS 1 PPS as the start and the SR620 1 kHz Reference
Out as the stop the standard deviation on the group of
500 is right at 9 nano seconds, but the mean value is
independent of the sawtooth error.
WRONG #2 - 50 ns
is the saw tooth size for the older 8 channel Motorola
timing GPS receivers, but the M12+T only has a 9 ns saw
Direction of Change
If the time interval has a
positive slope then the period of the FTS4060 is
increasing and so to reduce the period the frequency
should be increased and so the thumb wheel switches
should be moved to a higher number. This is for the case
where start is GPS and stop is the FTS4060.
One way to adjust the C field 3 digit thumb wheel pot is to
use GPS. Although there is some jitter on the GPS 1
PPS signal that amounts to maybe plus and minus 50 ns
(Motorola 8 chan), the accuracy over a 24 hour period is on
the order of 1E-12. The Motorola M12+T has about 9 ns
and so is much better. The GPS receiver should be used
directly. Also there a lot of jitter on the 1 MHz
FTS4060 output, much better to divide it down to 1 kHz or 1
It seems that the scale factor for the /S24 using is 1E-13
per count NOT the 2E-14 in the normal FTS4060 manual.
9 Jan 2005 - Plot
10 Jan 2005 - Plot
of nano seconds of Time Interval vs seconds of running
for s/n 1013 - 5.9E-12?
12 Jan 2005 - Plot
- Between 124,920 and 169,680 (12.4 hours) the 1 PPS input
to the PRS10 was removed and when reconnected caused a
negative swing that lasted until 248,400 seconds. But
it appears that a C-Field setting of 913 is pretty close to
correct. The drift is in the e-13 ot E-14 area.
18 Jan 2005 - Plot of s/n1013 vs. s/n 1227
, 1227 vs GPS
& 1013 vs GPS, now using s/n 1227 as 10 MHz ref for SR
s/n 1227 has it's C Field set at 600 as received from Govt
Liq. and it appears to be moving at -3.6E-12. s/n 1013 seems
to be moving at 5E-10 more like an OCXO than a Cesium, but
the Lock LED is on and the beam current peaks as it
should. What wrong?
1 Feb 2005 - s/n 1227 - I tried to use the time interval
between GPS and the 1 Mhz output to set the C Field by
getting the offset and then dialing in the correction (it
looked like the three thumb wheels were 1E-12, 1E-13 and
1E-14), but the resulting slope after a few days of
observation seemed to overshoot. A better way would be
to use a binary search where at each attempt you would half
the error. I think I have the setting to within a
single count on the finest wheel, but it'll take some days
10 Feb 2005 - s.n 1227 -
Still have C field at 544
. The 10 day plot shows
GPS wandering within a 150 ns range so the poorest stability
might be 1.7E-13, but an average would be more like parts in
10 Feb 2005 - Enabled Ionospheric correction in GPS receiver
and the delta time jumped up to the 500 ns range, so this
may account for the 100 or or ns variation the last 10
days. More time will tell.
11 Feb 2005 - changed GPS to track 4 highest satellites and
changed elevation mask to 30 degrees.
It's very important that the GPS receiver is properly
setup to get the best timing results.
28 Feb 2005 - The C field
has been at 570
for about 9 days and on average there
does not appear to be any drift, but it's difficult to tell.
2 March 2005 - To improve the stability of the GPS 1 PPS I
increased the elevation mask again, this time from 30
degrees to 50 degrees. It has made a big
improvement. The standard deviation after 1,000
seconds worth of 1 PPS averaging is now in the 30 ns area
where before it was in the 200 ns area. During 3 days
of observation there never was a time when there were no
satellites above 50 degrees. Since I'm running the GPS
receiver in the timing mode (known antenna position) only
one satellite is needed for a timing solution.
8 March 2005 - C filed at
- After the problem with the 4060 going crazy
after a beam current centering. Needed to cycle power
to get good operation.
13 March 2005 - Yesterday the counter got unplugged, but
neigher the FTS4060 nor the Austron 2100T were
unplugged. Both of these instruments have warning LEDs
that would indicate a loss of mains power, but the FTS-4060
output frequency became more unstable after this
event. This morning I unplugged the FTS4060 for 10
seconds and restarted it. After that the standard
deviation on the time interval improved from over 300 ns to
more like 30 ns. Maybe there are some power supply
caps that need replacing or more caps need to be added?
Also the amount of averaging on the GPS 1 PPS needs to be
increased. At 1,000 averages the best stability that
can be seen in one day is about
(3 * 35 ns * 2) / (SQRT(1,000) * 86400) = 7.6E-14, but
by going to 5,000 seconds the system improves to
3.4E-14. So starting a new plot.
15 April 2005 - Switched to an SynPaQ/III with Motorola
M12+T GPS receiver. This unit has 3 to 4 times less
variation than the old 8 channel UT+ GPS receiver. But
there appears to be a parabolic change in the plot
over the past 5 weeks
that I don't understand. The C filed has been at 568
since 20 March 2005.
28 April 2005 - the plot for s/n 1227 vs both GPS and
Loran-C still appears to be parabolic
indicating some type of aging which is NOT supposed to occur
whith a Cesium source. Aging is about -3E-14 per day.
29 April 2005 - the aging
seems to be slowing down. It's now
1 Feb 2006 - s/n 1013 seems to be working after having all
the modules taken apart (working on technical manual) and
then put back toghther again on 9 Dec 2005. Changing
the C-field causes a change that takes about a week to
settle down (now C=850) and for the last few days the 1 PPS
has stayed within about 1 ns of the Motorola M12+T pulse
(maybe 1ns/3 days = 4E-14).
6 Feb 2006 - s/n 1013
is showing drift like s/n1227. The equation for s/n
y = 2.7943x2 - 302.64x + 8969.4
and the quality of fit is
R2 = 0.9088. The x-axis is in days and the y-axis is
The first deritive of the equation has a first term of 2 *
2.7943 * x ns/day or +5.3E-14 drift rate.
I don't know if this is a measurement problem or a problem
with the FTS4060 standards.
9 March 2006 - The apparent parabolic aging was a
measurement problem related to setting the time interval
counter trigger level improperly (50 Ohm source and load TTL
should be at 1.25 Volts, NOT 2.4 volts).
Now s/n 1013 is looking very good. Another problem may
have been that the Ultra Stable Oscillator coarse frequency
was not set properly. It now has been centered and now
looks like +4E-13 offset which I'm trying to adjust to be
28 April 2006 -
GPS has some noise. For example the Motorola
M12T+ has a standard deviation of about 9 ns when
500 Time Inteval readings are averaged (reference is
some good oscillator). So you might expect
that the noise will peak +3 sigma and -3 sigma from
the mean value. This means that the offset you
can see is about 54ns/(measurement time in seconds).
to 4 min
min to 1 hr
to 4 hr
- 4 days
When plotting Time Intervals in Excel you can fit a
trendline and also get an R squared quality of fit
number. R^2 should be some number of nines for a good
fit. If it's not then there's something wrong.
17 May 2006 - there are times that last for about a couple
of hours whee the SR620 is displaying a standard deviation
for a 500 second average as high as a few hundred nano
seconds. I still don't know what causes this.
Some possible things that might cause it are:
- multipath may cause a problem if there was only one or
two sats visable, but I would think with 3 or more
visable a poor satellite would not cause a problem?
- no satellites at all would allow the GPS receivers 1
PPS to be coming from it's raw crystal
- some problem with the SR620 - I have disconnected the
PRS10 as the external ref since it's not needed and
between the PRS10, it's power supply, GPS receiver
there's just that much more to go wrong. But this
has not seemed t make any difference.
Instead of connecting the cesium 1 MHz signal to the
B input, connect the 10 MHz signal to the counter's
rear panel 10 Mhz input. Use SEL, SET &
SCALE^V to enable rear clock input. Then
connect the front panel 1 kHz Reference TTL
output to the B (stop) input. Now the rollover
will be every 1 mS, or a thousand times improvement.
The problem was
that the data was getting near the 1,000 uS
rollover point caused by using a 1 Mhz signal
for the counter B (stop) input.
If you're using Julian Day numbers (maybe 6
digits) and have less that 20% of the JDN worth of
data, the Excel trend line will be in error.
Much better to subtract a very large constant from
the JDN so that the x-axis starts from zero.
This way the trend line is correct.
The number of data points should be the same on
either side of a straight trend line. In my
case ALL the data points were on one side of the
The LORAN-C system will
continue and will be improved (2005) and offers a high
quality time transfer capability.
The Austron 2100F
will work for this
The HP 5060A manual says the
Zeeman frequency should be 42.82 kHz and about 1 volt
RMS. And that an error in the Zeeman signal of 1%
translates into a Cs frequency error of 3.6E-12, so it needs
to be set to within about 1 Hz. The amplitude of the
Zeeman signal and the C-Field can be adjusted, with the
modulation off and the loop open to set the C-Field, or the
C-Field can be measured by adjusting the frequency and
amplitude of the Zeeman input to get maximum beam current.
Mr. Pieter Zeeman won the Nobel
prize in Lecture 1902
along with Mr. Lorentz for
explaining a splitting in the spectral lines of light caused
by magnetic fields. This explanation was based on the
new things called "electrons", but did not take into account
quantum effects like up and down spins. His
experiments and the theory by Lorentz shed a lot of light on
what an "electron" was.
So far I don't have an audio generator that has the required
frequency settability AND enough drive power to do this
Corby D Dawson and Tom Van Baak have described how the audio
frequency for the Zeeman effect depends on the physics
package and I'm rephrasing it here. The definition of
the second is based on a Cesium standard running in a zero
magnetic field at sea level with a frequency of
9192.631770 MHz. Real Cesium tubes run with a very
small magnetic field and so their frequency is slightly off
that for a standard second, but the manufacturer knows how
far off and allows for it so that the final 10 MHz or 1 PPS
is exactly correct.
milli G 1
The C field coils in both HP and FTS Cesium tubes have the
same milli gauss per milli amp constant and so the C field
is determined by how the main frame is setup.
The synthesizer that generates the frequency that's fed to
the multiplier is also in the main frame and has a frequency
that matches the strength of the C field.
Note that as long as the C field and synthesizer are matched
to each other the system should work properly.
There may be an error reversing the synthesizer frequencies
of the HP5061A and HP5061B
Today, 15 June 2006, thre was a scheduled
power outage whicl PG&E replaced a power pole. Since
I still have not got the Austron 1290 Back Up power supply
operational, I juse connected a couple of 12 Volt 7 AH gel
cell batteries in series with a SB360 Schottky diode.
Using the male plug from a PC hard drive power supply "Y"
cable with the pins reinstalled so that black goes to black
(ground) and red goes to +30 and Yellow goes to orange (+5)
and with the diode cathode to the 4060 + 30 volt line the
batteries held up the 4060 for the 3 hours the mains power was
down. Now I have removed the batteries and a charging
them manually with a bench supply.
The 12V 7 AH lead acid batteries are 3.75" from the bottom to
the top of the metal terminals. The distance from the
bottom of the battery shelf to the bottom of the lid is about
3.75", so it would be a bad idea to try and close the lid with
the batteries inside. And there's an even more
compelling reason to NOT put lead acid batteries in the same
box as electronics. And that's because acid fumes from
the lead acid battery will literally eat the traces off the
printed circuit boards. So it's best if the batteries
are out of the 4060.
It took about 2.7 AH to charge one of the 12 V 7 AH batteries
and the power outage was about 2.7 hours, so the FTS4060 is
pulling about 1 Amp.
But the 7 AH rating is for a 20 hour discharge (350 ma) so the
battery will not last 7 hours at 1 amp. I think the
terminal voltage at the end of the power outage was about
23.49 volts or 11.75 volts per battery which is
discharged. Maybe 2.7 AH is the capacity at 1 amp?
When running from the batteries the Green Lock LED is on and
the red AC Power Alarm LED is on as well as the red Battery
LED. But monitor position 6 still shows 0 because there
is no charging current.
After AC power is restored the Power On Green and the red
Powere Alarm are both on (press the reset button to clear the
red alarm LED).
The green lock LED is still on. No battery LEDs are
on. (remember the /S24 has no battery option.)
Dead New Batteries
At first one of the new batteries not only would not put out
any voltage, but actually had reverse voltage across it and
the 4060 was still running. This means that the
switching supply will keep the 4060 going on less than 12
volts (although it may or may not start a cold 4060 on that
low a voltage). The "bad" battery looked just like the
good batteries when connected to the charging power
So now I have made up a simple 12 Volt
battery checker that's just a number 1156 car tail light
bulb soldered to a clip lead that was cut in half.
This pulls a couple of amps to light brightly and with only
1 amp will take some seconds to light dimly. This
works much better than the Radio Shack 22-080 battery tester
that shows a dead battery as good.
Note that the very common 12 V 7 AH batteries come with both
1/4" (0.250") and 3/16" (0.187) quick connect type
terminals. On the batteries I got some are 1/4" and
some are 3/16". So you need to check each battery,
even though at a quick glance they look the same.
Under the top cover the brick power supply is on the
right. Beside it is a tray that could hold rechargeable
batteries. There's a 4 position Molex connector with 3
sockets installed on wires that are Red, Black and Orange
marked "26" that's probably the battery pack connector.
There is a PCB behind the left metered panel and another PCB
behind the setup controls located behind the door on the
Chicago Miniature CMD series LED's.
Yellow CMD 53124A
The upper left box is marked Model 5030M/201/S25, s/n 199,
U.S. Patent 4499433.
Autolock for resonators for frequency standards Feb 12, 1985
A system is disclosed for examining the response
in atomic and molecular resonators to identify and select
the maximum resonant peak and the voltage used to cause said
peak to be produced. The system is fabricated of modular
elements electrically connected to a circuit board to
facilitate its construction and transportation with the
resonator. A microprocessor is utilized to perform the
analysis and to generate information to select the maximum
resonant peak, and the system includes means to compare the
value of successively generated resonator outputs and to
select the output with the maximum peak.
331 is Oscillators and /3 is Molecular resonance
The idea of this invention is to use a microcontroller (RCA
or Hughes 1802 CMOS) to sweep the control voltage to the 10
MHz OCXO across it's range and watch the CBT output peaks
and valleys. By looking for a peak with aproximate
equal valued adajacent valleys on both sides the maximum
peak can be selected and that peak used to lock the servo
system tying to CBT to the 10 MHz reference. The three
DAC1006 Digital to Analog converter chips that are part of
the A/D system reading the CBT output voltage is potted in a
clear compound probably to reduce elakage currents. J2
is the OCXO control voltage output.
Atomic beam tube June 29, 1976 250/251; 331/3; 331/94.1
by FTS (3967115.pdf
Other FTS Patents
Digital frequency generation in atomic frequency
standards using digital phase shifting February 24, 1998 331/3
Methods and apparatus for digital frequency
generation in atomic frequency standards February 3, 1998
Heater controller for atomic frequency standards
August 12, 1997 219/499
219/501; 219/505; 330/289; 331/1R; 331/69
Resonator package for atomic frequency standard
May 6, 1997 331/94.1; 331/3
System for producing spectrally pure optical
pumping light August 29, 1989 359/345
Adjustable crystal oscillator with acceleration
compensation May 13, 1986 331/156
Crystal oscillator assembly April 29, 1986 331/69
4899117 High accuracy frequency standard and clock system,
Vig; John R, Feb 6, 1990, 331/3 ; 331/176; 331/44; 331/47;
"Moreover, in rubidium
frequency standards, the available C-field adjustment range
limits the useful life of the unit. For example, in one of
the most popular rubidium frequency standards currently on
the market, the manufacturer provides a C-field adjustment
range equivalent to +1.5.times.10.sup.-9. The aging rate of
the standard is specified as 2.times.10.sup.-10 per year.
Consequently, at the specified aging rate, the limited
C-field adjustment range limits the useful life of this
rubidium frequency standard to 1.5.times.10.sup.-9
/2.times.10.sup.-10 =7.5 years."
5146184 Atomic clock system with improved
m, Cutler; Len, Sep 8, 1992, 331/3 ;
Inside the 4060/S24
J3 is the signal coming from the
I/F PCB of the CBT. J4 is the 450 Hz output to the A7
At the left rear is the
There is a 40 conductor ribbon cable connection, 2 coax cables
and a cable with 2 wires (Red and Black) going to A7 and TP2.
2:50 power on TP2 = 4.97 VDC and the front panel meter on 4
(control voltage) indicates about 5 volts. (2:50 pm)
2:56 Operation Monitor light turned off.
3:00 switching LOOP to Open and back to closed starts meter
into sawtooth from 0 to 5 Volts. It takes about 21 seconds to
sweep the monitor voltage from 0 to 5 Volts.
But TP2 is sitting at 4.98 VDC so must be a 5 Volt test point
or it's some logic indicator that may be pointing to a
21 July 2005 - A3-TP2 a test point to monitor the 450 Hz
signal that goes to A7.
The Cesium Beam Tube is on the right, marked: Cesium Beam
Tube, Model FTS-7103, p/n 08923-501, NSN 5960-01-214-7475.
To the left of the CBT at the rear is the 10 MHz oscillaotr,
marked: Model 1000B. In front of the 10 MHz osc. is The
A5 Distrubution Amp metal box with an SMA-f connector just
behind the front panel marked J3, RF1 which may be a 10 MHz
signal that could be connected to the front or rear
divider is the A3 Alarm PCB with 2 each DB-25 connectors and
no RF coax connections. Marked: D.1652 s/n 865009
(probably 1986 +...) It is not fully populated, missing a few
ICs and a number of discrete parts that probably are part of
the battery charging or monitoring circuit. The 30 VDC
brick power supply is up aginst the left wall.
I have named the DB-25m connector nearer the powr supply A3J1
and the DB-25m near the center divider A3J2 since there's no
markings on either.
A3J1 pins 23, 22, 24, 25, 2 and 6 are connected to the Monitor
thumb wheel switch positions 1 thorough 6 respectively and the
switch common goes through the front panel meter to ground.
The Battery Charge, AC Power Alrarm, Battery On andAC Power On
LEDs are connected to A3J1 pins 4, 5, 6 and 9 respectively.
Five of the wires on A3J2 are connected to the 5030 Assembly
A3J1 pins 1, 13 and 18 and connected to A3J2 pins 1,2,5,6,8,13
which is probably ground.
The Physics package might be
defined as the combination of the Cesium beam tube, the Times
51 Multiplier and the Interface PCB since the latter two items
are bolted to the side of the Cesium Beam Tube.
The Physics Package is in turn a part of the 5030
Assembly. In addition to the Physics Package the 5030
assembly has Most of the parts except the PS1 30 Volt power
supply and the A3 Alarm 5 x 6" PCB, and the front and rear
panels. The 5030 Assembly is 16 x 7.75 x 5 inches.
four 5/32" hex cap bolts, being careful to not let the 5030
assembly crash and move it so that you can easily get to the
SMA connectors and the #2 Philips screws on the "D"
Check to see that the 3 Coax cables are marked 4 (Zeeman audio
in), 5 (Rear 1 MHz out) and 7(Front 1 MHz out) that mate
to J4, J5 and J7, then disconnect these SMA cables.
Remove the two "D" connectors using a #2 Philips screwdriver
and lift the 5030 Assembly free of the chassis.
Note It is an easy job to
replace the 5030 Assembly and that may allow using the
complete 5030 Assembly from a working /S24 unit to bring a
defunct FTS4060 back on line. This can be done in a
few minutes. But I don't know where the additional
modules are located on a full featured 4060. If they
are on the right side ( the 5030 is on the left side) then
it would be very easy. If they are in the way of
removing the 5030 Assembly then it would take longer.
On the upper left is the 10 MHz OCXO.
A1A5 Dist AMP
At the upper right is the A5 Distribution Amplifier.
This amy be an A5/S24 with the front 10 Mhz output
A1A5 & A1A7 Sub Assembly
By first labeling all the coax
cable ends that will be disconnected, then by removing 2
(+) screws and loosening 2 (-) captive screws and
disconnecting some connectors (no soldering needed) the
combined A5 & A7 assembly can easily be removed.
A1A5 Distribution Amp
My units have an A5 amplifier that has a open SMA-f
connector facing forward and that connector has a 10 MHz
signal that's about 4.4 Volts Pk-Pk. But other /S24
units have the connector and some internal parts removed
and so don't have the 10 MHz easy to connect.
The cable from the A5 10 Mhz output to the rear panel is
about 40" long, SMA(m) on the A5 end and a bulkhead BNC(f)
for the rear panel
A1A2 Mother Board
seen once the A5+A7 sub assembly is removed. All the
components in the 5030 assembly interface to the mother
board. This greatly minimizes the wiring
clutter. There may be a dozen components on the
Max dimensions are about 12" x 5" although it's "L"
only the A1A2 motherboard and the A1A9 input filter at
attached to the 5030 frame.
The right hand narrow part is just to get the 40 conductor
ribbon cable lined up with the A1A3 uP board.
A1A6 Ultra-stable Oscillator
Dataum 1000B Ultra-Stable 10
MHz oscillator (now Symmetricom
). This is a brick about 3x3x7inches with
all the connections on one of the 3x3" ends. Part
number is 05818-119. There's a DB-9 connector with
the following pinout:
Ctrl Voltage in (-10 to +10)
tune in voltage
V ref (coarse tune hot)
VDC Oven power
The oven insulation is my means of a dewar. The
initial aging rate might be <1E-10 per day when new,
but can get below 1E-12 after running for some time.
The phase noise is lower than -134 dB at 10 Hz, -144 dB at
100 Hz and -157 dB at 1 kHz.
The 10 Mhz output is from a right angle SMB connector
pointing down. (All the small coax is terminated
with 50 Ohm SMB connectors in the FTS4060).
On top of the 1000B (p/n 05818-119) there's a coarse
frequency adjust pot.
To remove the USO three 1/4" nuts need to be removed that
are below the A3 uP board and the connectors disconnected.
on a hand picked 100B:
A1A7 x18 Mult & Mixer
Just under the A5 Amplifier is the
Times 18 Frequency Multiplier (10 MHz in, 180 MHz out) and
As seen in the photo the connectors are: 10 MHz in,
connector with Black, Gnd, and Red wires going to J4 on the
A3 Microprocessor board. Cable with Black, Red, Green
(ground) & blue wires soldered to feedthroughs going to
connector J4 on Cesium Beam Tube motherboard.. 12.6 MHz
input & 180 MHz output.
A1A8 Cs Power Supply
lower right corner is the A8 Power Supply for the Cesium
Beam Tube that includes the two HIGH VOLTAGE outputs.
The bottom of this PCB is visible at the top left front when
the top cover is removed. You might not
want to have your hands anywhere near this board when power
A1A9 DC Input Filter
and should be able to slide out, it's trapped by the female
thread fitting used to attach the 5030 sub assembly to the
chassis. It has a dual electrolytic cap, a single
electrolytic cap, a diode and an inductor.
A2 RF Assebmly
bottom center is the 3 x 7" A2/S24 RF Assembly
(56219-05280-011 Assy 05281) that takes in 10 MHz and
outputs 1 MHz. On a full featured 4060 this board
would also output 100 kHz and 10 MHz.
It may that the 74LS90 divide by 10 circuit could be
bypassed to allow two 10 MHz outputs instead of the two 1
MHz outputs that are on the /S24 versions.
A1A3 Micro Processor Board
board has a coax input (J2) that takes in the error signal
from the Cs interface board. It also has a coax EFT
output (J3) to drive the Ultra-stable 10 MHz oscillator
(A6). The 450 Hz signal is generated on this board
and feeds A7. 40 pin connector J1 has a number of
analog signal inputs and outputs as will as digital inputs
With J1 pointing up in the photo at left the two TO-5 cans
in the upper left are the +15 and -15 volt supplies for
the analog Op amps, sample/hold and DAC circuits comprsing
the left analog part fo the board.
The uP is an 1802.
DAC1006 D/A converters are used both for A/D conversion
with a comparator and for D/A output to the meter and
A1A4 12.6 MHz Synthesizer
same size board, the A1A4 12.6 MHz Synthesizer (56219 Assy)
that shares the same 14 conductor ribbon cable and has a
single coax cable that goes to the times 18
Multiplier. There are a half dozen Synchronous
Four-Bit Counter 54LS161
ICs on this board.
A1A1 Cesium Beam Tube Assembly (Physics Package)
tube is really straight, but the photo gives it a curved
appearance because of perspective.
The A1 Cesium beam tube is held at each end by an angle
bracket that has 3 large philips screws holding it to the
5030 frame. One of these is under the A8 power
supply and the other is under the A3 uP board.
The x51 Multiplier and the Cesium Beam Tube Interface PCB
are attached to the tube.
Connections to the rest of the system are by means of:
Red & white High voltage wires, twisted pair of orange
wires to Cs PS
coax with 180 MHz from A7 to X51 mult.
26 conductor ribbon cable to mother board W5
Coax with error signal from interface board to A3 uP
wires coming out of the CBT are soldered. The E26
Test Point is missing. The wires coming from
theDetector Heater are labeled along with the "E" number
of the board terminals.
X51 Microwave Multiplier
The x51 Microwave multiplier gets it's RF input from the
A1A7 X18 Multiplier - Mixer and feeds it's output to the
waveguide adapter on the CBT. The Red, Green and
Black wires come from the CBT interface PCB.
PCB Rails but no Card Edge Connectors
The PCBs are held by rails, but there are no card edge
connectors on the PCBs. All connections are made by
coldered wires, coax connectors (typcially standard 50 Ohm
SMB), or rectangular connectors. There is an unused
pair of rails above the microprocessor PCB, but if another
board is used there it would ned to have notches to clear
the to coax connectors coming from the uP board.
Manual Control Voltage & Loop Gain
In Appendix A of the Operation
Manual it describes how to manually set the Control Voltage
and Loop Gain. The symptom indicating that this needs to
be done is that when the Monitor is set to 4, Control Voltage,
the needle ramps up and jumps down and this is repeated over
and over. This was the symptom my unit had so I manually
adjusted these two settings as follows after over 30 minutes
of warm up:
- Open door and turn off "MOD" and set "LOOP" to OPEN,
- At the same time press "Align" (behind the door) and
"Operation Alarm" (next to the Monitor LED). This
stops the control voltage from searching.
- Set the "Manual Scan" switch (behind the door) to
"Control Voltage" and set the Monitor switch to 4 (control
Voltage) and use the "Manual Scan Increase/Decrease"
switch to center the meter.
- Set the "Manual Scan" switch (behind the door) to to
"Loop Gain" and set the Monitor switch to 3 (Beam) and and
use the "Manual Scan Increase/Decrease" switch to center
- Switch the "MOD" and "LOOP" switches back to On and
Closed. In my case this caused the Lock LED to turn
on and stay on.
26 Feb 2006 - Note after
almost getting the C field set on s/n 1013, there was a
power failure lasting about 2 seconds. But 1013 had
been running for many months and was working well.
After the power came back on the lock LED did not
light. After giving it about 4 hours still with no
lock light, the above procedure was used to set the control
voltage and loop gain, and afterwards the lock LED turned on
as soon as the closed loop and mod on switches were thrown.
28 Apr 2006 - You really can only center the Control Voltage
using the front panel controls (as described above in the
OPEN mode). When there's a continuous search or the
yellow monitor LED is on with the green LOCK LED, then it's
time to adjust the coarse frequency of the crystal
oscillator. This can be done with the source
locked. Remove the bottom cover and with the monitor
switch in position 4 (CONTROL) note the reading. In my
case it was over 3. Then adjust the coarse pot on the
USO to bring the needle a little to the other side of 2.5,
in my case to 1.6. When the control voltage gets
closer to 2.5 the yellow monitor LED will go out leaving
only the two green LED for LOCK and AC power.
Hint: leave the door slightly open by turning the screw all
the way out, closing the door and then turning the screw 1/4
turn. This way if the ALIGN lamp turns on you can see
it. You could leave the door open, but for me it's in
the way of other stuff.
Manual Loop Gain
On the Cs Beam Tube Interface PCB there
are 2 10-turn pots. The one close the the SMB connector
is R9 and should not be changed. The one next to R9 is
R5 and is the manual beam current adjust. It should be
set so that the voltage between E23 (ground) and E26 (a test
point) is 1.8 +/- 0.2 VDC. But I can't find E26 on my
unit. Where is it?
Also note in the photo there is a small screwdriver adjustment
on top of the 10 MHz OCXO that has been relocated from the
front so that you do NOT need to remove the 5030 Assembly to
get access to this coarse adjustment pot.
Serial Number 1013 has had the Green Lock LED on for about 3
hours. If the line cord is removed and plugged back in
after 15 seconds the unit Lock LED turnes on in about 10
The manual implies that you
can make the loop gain or beam current adjustments on the
fly. But on the two occasions that I have tried to do
that the FTS4060/S24 gets confused. The fix has been
to pull the line plug for about 15 seconds and
restart. Without the restart the control loop is
The Austron 2100T Timing LORAN-C
makes a good accessory. It provides a UTC
clock, 1 PPS output and a check on the stability of the
FTS4060. Also if the reference input fails the 2100T
will break lock and need to be manually re started and so it's
a good monitor on the output of the reference source.
If you have one of the /S24
units would you tell me if you have the 10 MHz output and your
If you have brought a unit back to life tell me what you