KVARZ CH1-76A User manual

CH1–76А
PASSIVE HYDROGEN
MASER
OPERATING MANUAL
2.721.655–01 OM
INSTITUTE OF ELECTRONIC MEASUREMENTS “KVARZ”
176, Prospect Gagarina, Nizhny Novgorod, 603009, Russia.
Tel.: [phone].
Fax: [phone].

2
Fig.1. The CH1–76A Passive Hydrogen Maser

3
1. SAFETY PRECAUTIONS
The CH1–76A Passive Hydrogen Maser is referenced to the O1 Class category of electrical
protection for instrument.
Inspection of protective grounding should be done before all other connections and ground terminal
disconnection of is made.
When the Maser is used together with other units, instruments or in a system, it is necessary to
ground all units.
Do not touch any current-carrying components during repair or component operation check, as line
voltage 110/115/120/220/240 V and 3.5 kV dc voltage is present.
Switch off the Maser before component replacement.
Attention! Discriminator ion pump supply circuits, power supply high-voltage divider and check
circuits, marked with the warning sign of hazardous voltage “ “ have potential 3.5 kV relative to
the case. Safety interlock terminals are located on the power supply output connector.
Any protective grounding break inside or outside the Maser or ground terminal disconnection may
cause danger for the user.
Grounding disconnection is prohibited!

4
2. CONTENTS
1.
Safety Precautions
3
2.
Contents
4
3.
List of Figures
5
4.
List of Tables
6
5.
Description
7
5.1.
The Maser CH1–76A Application
7
5.2.
The Maser CH1–76APrinciple of Operation
7
5.3.
Design
10
5.4.
Marking and Sealing
10
6.
The Maser CH1–76A Setup
11
6.1.
Unpacking and Repacking
11
6.2.
Installation
11
6.3.
Preparation for Use
11
7.
The Maser CH1–76A Operation
13
7.1.
Operating Controls and Connectors
13
7.2.
Preparation for Measurements
16
7.3.
Measurement Procedure
18
8.
Specifications
19
9.
Storage and Transportation
24
10.
The Maser CH1–76A Composition
25

5
3. LIST OF FIGURES
1.
The CH1–76A Passive Hydrogen Maser
2
5.1.
The Maser CH1–76A Simplified Block Diagram
8
5.2.
The Maser CH1–76A Detailed Block Diagram
9
6.1.
The Maser CH1–76A Package Design
12
7.1.
The Maser CH1–76A Front (A) and Rear (B) Panels
14
10.1
The Maser CH1–76A Maser Accessory Kit
26

6
4. LIST OF TABLES
7.1.
Operating Controls and Connectors
13
7.2.
Adjustable Voltage and Currents
17
8.1
The Maser CH1–76A Specifications
19
8.2
The Maser CH1–76A Errors
21
8.3.
The Maser CHI–76A Interface Functions
21
8.4.
The Maser CHI–76A Programmable Modes
21
8.5.
Frequency Tuning Programming Code
22
8.6.
Output Data Format
22
8.7.
Diagnostics Data Format
22
8.8.
Diagnostic Data
23
8.9.
Status Byte Output
23
10.1.
The Maser Composition
25

7
5. DESCRIPTION
5.1. THE MASER CH1–76A APPLICATION
The Maser CH1–76A Passive Hydrogen Maser is used as a highly stable signal generator for time-
frequency measurements and for applications in reference measurement systems.
The Maser CH1–76A external view is shown in Fig. 1.
Typical applications are: national time and frequency calibration services and systems, navigation,
radiolocation, high precision physical measurements, metrology, frequency measurement
equipment, calibration of rubidium and cesium frequency standards, long baseline
radiointerferometers, telephone network timing, checkout equipment for GPS–GLONASS based
timing systems, etc.
The Maser CH1–76A is ruqqed, small size, relatively lightweight, transportable and highly stable
oscillator. It can be used in automated measuring systems by controlling the Maser's synthesizer
frequency and diagnostics state through the GPIB interface.
5.2. THE MASER CH1–76A PRINCIPLE OF OPERATION
The Maser CH1–76A is a Passive Hydrogen Maser.
Block diagrams (Fig. 5.1 and 5.2) describe the Maser's principal of operation.
It is based on the crystal oscillator frequency (fq) locking to the hydrogen discriminator atomic
emission line frequency. The influence of discriminator's RF cavity frequency (fc) fluctuations on
the emission line frequency is eliminated by the RF cavity frequency (fc) adjustment of the crystal
oscillator frequency (fq).
The automatic frequency control (AFC) unit through 5 MHz signal modulation with 12.5 kHz forms
a FM excitation signal. This signal is then multiplied by 20 and mixed with the frequency
synthesizer 20.4057 MHz signal. Finally, the 1420.405 MHz excitation signal is separated directly
in the
discriminator RF cavity from the 100 MHz signal 14th harmonic and synthesizer signal interaction.
In the atomic emission line and RF cavity discriminator interaction FM signal is converted into an
AM-FM signal. This signal envelope amplitude and phase data contain information about the
crystal oscillator frequency deviation from hydrogen atom emission line frequency and information
about the frequency fcdeviation from frequency fq. The discriminator output AM–FM signal again
passes to AFC unit, where it is amplified, converted and detected. After the amplitude detector 12.5
kHz signal is
applied to the selective amplifier, the output is connected to two-phase shifters. With the help of
these phases shifters RF cavity and crystal oscillator error signals are separated. From the phase
shifters the signals pass to two synchronous detectors. The 12.5 kHz reference signal is applied
simultaneously to the synchronous detectors. Then the synchronous detectors output signals are
applied to 2 integrating amplifiers, the output signals of which control the RF cavity and crystal
frequency.
The GPIB Interface enables the use of the Maser in automated measuring systems.
The Interface is designed to control the synthesizer frequency via an external computer and to
transfer the Maser's state diagnostic data.
Since the Maser CH1–76A internal systems have different warm–up times (Discriminator –
10 hours, other units –2 hours), they should be switched on separately as specified in the Operating
Manual.
In case of an AC power failure the Maser CH1–76A automatically switches to the external DC
power supply +(22–30) V, preserving its operating characteristics (assuming a DC supply is
connected).

8
Fig. 5.1. The Maser CHI–76A Simplified Block Diagram

9
Fig. 5.2. The Maser CH1–76A Detail Block Diagram

10
5.3. DESIGN
Two lateral brackets, mounted between the front and rear panels, serve as main Maser load–
carrying structures. The upper and bottom covers with ventilation openings can be easily removed.
The Maser case is divided to two equal pads by a vertical plate. The Hydrogen Discriminator, Oven
Control Unit and Beam Stabilizer are mounted in the left part. Power supply, AFC and control units
are located in the right part.
An easy access to the Maser units and assemblies through the upper covers provides a high level of
maintainability. A removable cover on the rear panel provides access to HF Oscillator of Hydrogen
Discriminator.
Electronic units are in Al cases and card cages for PC card insertion. Interplane connection is
provided by motherboards.
5.4. MARKING AND SEALING
Instrument name and manufacturer trademarks are located on the upper left corner of the Maser
front panel.
The Maser Serial number and the year of manufacture are indicated in the upper left corner of the
rear panel.

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6. THE MASER CH1–76A SETUP
6.1. UNPACKING AND REPACKING
Remove seals and steel band from the shipping container. Open container cover, take the packing
list.
Remove corrugated boards and out packing box.
Remove the seal from packing box cover, remove documentation and accessories.
Remove the second seal from the packing box, release shock absorber nuts, open the cover and
remove the Maser.
For shipping, use shock absorber, packing box and shipping container. Before shipping pack the
Maser as follows.
Put the Maser into polyethylene bag, fix it in shock absorber, put into packing box and tighten nuts.
On the top of the packing box put all the necessary documentation and accessories.
Close and seal the packing box.
Put the box into the shipping container with waterproof paper inside. Between the shipping and the
packing boxes walls insert packing material. Put packing list on the top of the corrugate cartoon
under waterproof paper.
Fix the shipping container cover, put the steel band and seal the container.
The Maser CH1–76A package design is shown in Fig. 6.1.
Place the following signs on the upper left corner of front and sidewalls: "TOP", "CARE", "DO
NOT TURN OVER" signs and the date of packing the unit. Install a "TIP–AND–TELL" indicator
of the container (if available).
6.2. INSTALLATION
Study Section 6 before using the Maser.
Check the Maser after unpacking.
Perform visual check and be sure that:
seals are preserved;
the kit is in accordance with Section 10;
no visual mechanical defects;
all controls are fixed in their positions, their rotation is smooth and all fuse links are present, etc.;
terminals and connectors are clean.
Operating ventilation opening must be free.
6.3. PREPERATION FOR USE
It is recommended that the Operating Manual be studied before putting the Maser into operation;
study front and rear panel controls functions and positions (Section 7.1).
Put the Maser CH1–76A in a place that provides operating convenience and natural ventilation.
Avoid magnetic field with fluctuation amplitude more than 30 A/m and vibration influence on the
Maser.
Attention! Before turn the Maser on set the required line frequency and voltage section on the rear
panel of the Maser (position 25 in Fig. 7.1(B)).
Connect ground terminal to the Maser case and set the Maser controls into initial positions (see
Section 7.1).
Power switch must be in "OFF" position. If the Maser was shipped and stored in conditions, which
differ from operating ones, let Maser warm up for 10 hours under operating conditions. Plug the
power cord into AC socket.
Attention! If the Maser is off for long period operate once a month by turning on and drive
discriminator ion pumps as described in Section 7.2.

12
Fig. 6.1. The Maser CH1–76A Package Design

13
7. THE MASER CH1–76A OPERATION
7.1. OPERATING CONTROLS AND CONNECTORS
Operating controls and connectors are located on the front and rear panels of the Maser (Fig. 7.1).
The functions of operating controls and their initial positions are given in Table 7.1.
OPERATING CONTROLS AND CONNECTORS
Table 7.1.
Position in
Fig. 7.1
Operating controls or
connectors designation
Description
Initial position
1
2
3
4
1,2
AC PWR ON/OFF
Toggle switch - switches the
Maser on.
LED indicator –the Maser
switches on indication.
Down
3,4
DC PWR AVAIL
DC PWR ON
LED indicator –battery
switches on indication.
5
TIME
LED indicator –indicates Maser
operation from battery.
Digital indicator –current time
in hours, min., sec.
Indication of synthesizer setting
by "FRQ.ADJ." code switch
according to "INDICATION"
switch position.
6
ERROR
Digital indicator - Maser error
indication in accordance with
the error table on the front
panel.
8
TIME NUMBER
Buttons –current time setting.
7,9
AFC CRYST
Toggle switch –crystal
oscillator AFC unit switches on.
Multi-turned potentiometer sets
crystal oscillators initial
position.
Down
10
FRQ. ADJ.
Code switch –5 MHz output
frequency variation.
Look at
Table 10.1
11
TIME DIGIT
Button –digit selection, in
which current time is set by
"NUMBER" button.

14
Fig. 7.1. The Maser CH1–76A Front(A) and Rear(B) Panel

15
Table 7.1(cont.).
1
2
3
4
12,14
AFC CAVITY
Toggle switch –discriminator down
RF cavity AFC unit switches on.
Multi-turned potentiometer sets RF
cavity frequencies initial position.
Down
13
INDICATION
Slide switch –switches "FRQ.ADJ"
down code or "TIME" code on
indicator.
Down
15
I
Button –ion pump current check.
16,18
CHECK
Switch –switches standard test points
to "CHECK" indicator in the
following positions:
1st position: 2–nd harmonic;
2nd position: crystal stat;
3rd position: cavity stat;
4th position: purifier current;
5th position: +27V;
6th position: +18V;
7th position: +12.6V;
8th position: –12.6V;
9th position: +5V;
10th position: 5 A;
11th position: 50 A;
12th position: 500 A.
Micro–ammeter –operating mode
indication of power supplies and
instrument separate units.
17
U
Button –ion pump voltage check.
Down
19
PUMP
Toggle switch –ion pump switch on.
20
AFC SUPPLY
Toggle switch –AFC unit switch on.
Down
21
HFO
Toggle switch –turns on HFO of
atomic hydrogen source.
Down
22
IHFO
Button –IHFO check
23
5 MHz
Connectors –5 MHz signal outputs.
24
SYNCH. DET 1
Connector –crystal oscillator AFC
unit synchronous detector signal
output.
25
115/120/220/240V
50/400Hz
Plug –line frequency and voltage
selection.
Required line
frequency and
voltage
26
IF
Connector –19.6 MHz IF signal
output used only during adjustment,
instrument repair and Zeeman
frequency (fz) measurement.

16
Table 7.1(cont.).
1
2
3
4
27
SYNCH.DET2
Connector –discriminator cavity
AFC unit synchronous detector
signal output.
28
1 Hz
Connectors –1 Hz signal output
29, 30
SYNC. ON
Connector –1 Hz signal for time-
scale synchronization.
Slide switch –time scale
synchronization switches on.
Down
31
LINE
Power cord output.
32
FA FA
AC line fuse links.
33
Terminal –instrument case
connection.
34
GPIB
Connector –interface connection.
35
ADDRESS
Slide switches –instrument address
setting in the interface.
Down
36
REMOTE
Slide switch –synthesizer frequency
remote control switch on.
Down
37
=24 V 0N
Toggle switch –DC power supply
switch on.
Down
38
=24 V
Connector –DC powers supply
connection.
39
FA 5A
DC line fuse links.
40
FZ
Connector –LF input signal for
Zeeman frequency measurement
41
Hydrogen source pressure meter.
7.2. PREPERATION FOR MEASUREMENTS.
Check the control positions. They must be set in the initial positions as given in Table 7.1. If
necessary connect the Maser to the external DC power supply +(22–30)V.
Set "Line" switch (position 1 in Figure 7.1(A)) to "ON" position. The "AC PWR" indicator
(position 2 in Fig. 7.l (A)) must light on. Set "= 24 V ON" toggle switch (position 37 in Fig. 7.1(B))
to "ON"
position. "DC PWR AVAIL" indicator (position 3 in Fig. 7.1(A)) must light on.
Set "CHECK" toggle switch (position 16 in Fig. 7.1(A)) to the 6th position ("+18V" position) and
check +18 V power supply voltage. "CHECK" indicator (micro-ammeter –position 18 in Fig.
7.1(A)) readout must correspond to the value given in Table 7.2. If it differs from Table 7.2 address
IEM KVARZ as given in Section 13!
Set "CHECK" toggle switch to the 12th position ("500 A" position). Set "Pump" toggle switch
(position 19 in Fig. 7.1(A)) to "ON" position. Check ion pump operation pushing U and I buttons
(positions 17 and 15 in Fig. 7.1(A)). Voltage in discriminator must increase and current decrease.
They must change to values according to Table 7.2.

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CONTROLLABLE VOLTAGES AND CURRENTS
Table 7.2.
Control
switch
position
2nd
harmonic
Crystal
stat
Cavity
stat
Purifier
current
+27V
+18V
+12.6V
IHFO
Micro-
ammeter
indications
3510
10
10
305
4010
4010
4010
2510
Table 7.2(cont.).
Control
switch
position
–12.6V
+5V
5 A
50 A
500 A
Micro-
ammeter
indications
4010
4010
U 355
3510
3510
I 2525
0
0
Set "CHECK" toggle switch to the 11th and I2th positions ("50 A" and "5 A" positions) one after
another because of ion pump current decreasing. In 30 minutes the ion pump current has to be < 30
A.
Set "AFC Power" toggle switch (position 20 in Fig. 7.1(A)) to "ON" position.
Check +12.6V - 12.6V, +5V source and purifier current values according to Table 7.2 using the 7th,
the 8th, the 9th and the 4th positions ("+12.6V", "–12.6V", "+5V" and "Purifier current" positions)
of "CHECK" toggle switch respectively.
Figure "4" must light on at "Error" indicator (position 6 in Fig. 7.1(A)). After "AFC power toggle
switch is set to "ON" position wait for 5 minutes and set " HFO" toggle switch (position 21 in
Fig. 7.1(A)) to "ON" position. Check +27V power supply using the 5th position ("+27V" position)
of "CHECK" toggle switch.
Then push the button "IHFO"(position 22 in Fig. 7.1(A)) and test HFO current according to Table
7.2.
Figure "5" at "Error" indication can light on for a short time. During this short time there is no light
on the backside of the Maser. Then this light must appear and Figure "5" at "Error" indicator must
disappear the same moment.
Set "HFO" and "AFC Power" switches to "OFF" positions. Warm up the Maser during 10 hours and
then Figure "4" at "Error" indicator must disappear for " AFC Power" switch in "ON" position.
Check the hydrogen source pressure with the pressure meter (position 41 in Fig. 7.1(B)). The
pressure must be 150 Pa.
Set "AFC Power" toggle switch to "ON" position and check the Maser operation according to
Table 7.2 once more without positions 1, 2, 3 and 5.
Set "CHECK" switch to the 3rd position ("CAVITY STAT").
Set "AFC CAVITY" toggle switch (position 12 in Fig. 7.1(A)) to "ON" position. Rotating
potentiometer knob (position 14 in Fig. 7.1(A)) set the needle of the indicator to 0. The indicator
needle must follow the rotating directing of the potentiometer knob. The setting is correct when the
needle slightly swings to the left and to the right from the operating point 0. Fix the potentiometer
knob
position on 0.
Set "CHECK" switch to the 1st position ("2–nd harmonic"). Set "HFO" switch to "ON" position.
Figure "5" at "Error" indication can light on for a short time.
During this short time there is no light on the backside of the Maser. Then this light must appear

18
and Figure "5" at "Error" indicator must disappear the same moment.
Rotating "AFC CRYST" potentiometer knob (position 7 in Fig. 7.1(A)) very slowly get increasing
of the 2nd harmonic value on the micro-ammeter. The same moment Figure "1" at "Error " indicator
can blink. Set "AFC CRYST" toggle switch to "ON" position. Be sure the potentiometer is set
correctly. For this set "CHECK" switch to the 2nd position ("CRYST STAT" position).
Rotate "AFC CRYST" knob of the potentiometer very slowly and set the indicator needle to 0. The
micro-ammeter needle must follow the rotation direction of the potentiometer knob. During rotation
"AFC CRYST" potentiometer knob Figure "1" at "Error" indicator can blink. Indicator needle must
swing to the right and to the left near the operating point 0. Fix the knob position on 0.
If you have any problem to set the operating mode of the Maser contact IEM "KVARZ" as given in
Section 13.
In order to provide maximum specifications to perform precision measurements it is necessary to
provide maintain temperature (1C) and avoid external magnetic field variation.
Check "FREQ.ADJ." code switch set according to the Table 8.1.
If the Maser is integrated into ATE it is necessary to connect it to GPIB and to set the Maser
address with rear panel switch. Look Section 10 for using the Maser into ATE.
7.3. MEASUREMENT PROCEDURE
The Maser provides the only one operating mode: continuous output of 5 MHz sine and 1Hz pulse
signals with parameters given in Section 8.1. These signals are applied to "1 Hz" and "5 MHz"
outputs. These signal specifications should be in accordance with requirements of Table 8.1. To
synchronize the Maser 1 Hz pulse signals, it is necessary to connect external 1 Hz pulse signal to
synchronization input on the Maser rear panel (position 29 in Fig. 7.1(B)) and set the switch
"SYNC" to "ON" position
(position 30 in Fig. 7.1(B)) for 2–3 seconds.
Synchronization error has to be in accordance to requirements of Table 8.1.

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8. SPECIFICATIONS
The Maser specifications are given in Table 8.1.
THE MASER SPECIFICATIONS
Table 8.1.
Parameter
Specification value
Measured value
1.Frequency Accuracy and Stability:
Accuracy
1.510–12
(within 3 years)
_________
Setting at shipment*
Retrace
310–14
(after 24 hours of operation)
Stability y(2,)
at time interval 
l s
710–13
l0 s
1.710–13
100 s
510–14
1000 s*
210–14
1 h*
110–14
1 day*
410–15
Frequency Aging*
210–15/day
Temperature Coefficient
210–14/C
Magnetic Sensitivity
510–14/2 Oersted
2. Frequency Settability:
Range
At least 110–10
1.000010–10
Step Size
110–14
Synthesizer Code Switch
Nominal Position
0000–9999
____________
Record Setting
3. Sine Output Signals
(2 isolated outputs):
5 MHz
Amplitude
10.2V rms
(into 50 Ohm load)
Harmonic Distortion
–30 dBc
Non-Harmonic Distortion
–100 dBc
Phase Noise
(SSB, 1Hz B.W., dBc/Hz)
1 Hz
–100
10Hz
–120
100 Hz
–140
1000Hz
–150
10 kHz
–150
4. Clock Output Signals
(2 clock isolated outputs):
1 Hz (1 PPS)
Amplitude
> 2.5V Peak into 50 Ohms (output levels are TTL compatible)
Width
10–20 s
Rise time
< 30 ns
Jitter
< 0.1 ns rms

20
Parameter
Specification value
Measured value
5. Clock Synchronization
to within 200 ns of Reference Pulse:
Sync pulse
Amplitude
2.5–5V
Width
1–100 s
Rise Time
< 100 ns
Input Impedance
50 Ohms
Time Reference
Rising edge
6. Power Requirements**
Input voltage
AC
100, 120, 220V10 %, 240V5 %,
45 to 65 Hz
DC (external)
+22 to +30V
Power Consumption
AC
< 140 VA
DC
< 90W
Emergency Automatic
Switch to DC Verified
Warm-Up Time
< 10 hours
7. Environmental
Temperature:
Operating
+5 C to +40C
Non-operating
–0C to +50C
Humidity
Operating
to 80% at +25C
Non–operating
to 98% at +25C
Atmospheric Pressure
Operating
84–106 kPa
(630–795 mm Hg)
Non–operating
12–106 kPa
(90–795 mm Hg)
8. Physical:
Dimensions
Without package
280480555 mm
(11"19"22")
In package case
682730800 mm
(27"29"31")
Weight:
Without package
55 kg (120 lbs)
In package case
105 kg (230 lbs)
9. Warranty
27 months
10. MTBF
9000 hours
11. Service Life
15 years
* Specified only under laboratory conditions:
at 1C ambient temperature change in operating temperature range;
humidity 30% to 80%.
** In case of an emergency the Maser automatically switches to the External DC power supply +22 to
+30V.