KVARZ CH1-76A Bedienungsanleitung
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.: (+7) 831–4652293, (+7) 831–4667093.
Fax: (+7) 831–4652293, (+7) 831–4665562.
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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