The CH1-75 Active Hydrogen MASER is one of the most stable frequency sources over time intervals from 1s to several months. Its frequency stability over these time intervals exceeds the stability of the best caesium frequency standards. The CH1-75 principle of operation is based on a forced hydrogen atom emission in the storage quartz bulb located in the microwave cavity. At large enough atom density in the bulb and high Q of the microwave cavity, the CH1-75 self-excitation takes place and it begins generation at 1420.4 MHz frequency. The CH1-75 emission signal is amplified by the sensitive crystal oscillator. In such a way a high frequency stability of the MASER is transferred to the crystal oscillator.

• National Timekeeping
• National Frequency Standards
• Deep Space Navigation
• Fountain Caesium Reference
• Navigation
• Telecommunications
• GNS Ground Control
• GPS Satellite Monitoring
• Astro Laser Range Finding
• Astronomy
• Baseline Definition
• Calibration
• Calibration of Caesium or Rubidium
• Climatology
• Defense
• Determination or Earth Rotation
• Earthquake Research
• Fast Missile Tracking
• Geodesy
• Geodynamics
• Glacial Movement
• Gravity Prospecting
• Intelligence
• Plate Tectonics
• Position fixing
• Secure Communications
• Space Navigation
• Support of Radar

Frequency Outputs  
(2) 5MHz, sine 50Ω, 1±0.2 Vrms
(2) 100MHz, 50Ω, 1±0.2 Vrms
(2) 1Hz (1 pps) 50Ω, >2.5V peak
Pulse Width 10 to 20 μs
Rise Time 15 ns
Jitter 100 ps

Clock Synchronization  
Automatic within 50 ns of reference pulse  
Width 1 - 100 ms
Rise Time 20 ns
Input Z 50Ω

Stability (5MHz & 100MHz Allan Variance)  
Avg Time σy(2,τ) Autonomous Auto tune  
1s 2E-13
10s 3E-14
100s 7E-15
1000s 3E-15
1 hour 2E-15
1 day 3E-16

Aging Autonomous Auto Tune
At Delivery After 1 year operation
≤5E-16/Day ≤3E-16/Day

Accuracy Autonomous Auto Tune
  ≤5E-16 over 5 year period

Frequency Trim Range At least 1E-10
Setting Resolution 1E-14 Steps

Phase Noise (dBc)

Hz from carrier 5MHz outputs 100MHz outputs
1 -110 -85
10 -130 -105
100 -140 -115
1000 -150 -125
10000 -150 -125

Harmonic Distortion <-30dBc (5MHz output)
Frequency Measurement Error (RMS)
of built-in comparator

1E-13 per 1 sec
1.5E-14 per 10 sec
3E-15 per 100 sec
5E-16 per 1 hour or more

Power Input - AC 115/220 Vac, ±10%, 45 to 430Hz
  <150 VA power consumption

Power Input - DC (automatic battery back-up)
As an alternative to AC, the CH175 can be powered by
an external 22-30 VDC supply. <100 watts power consumption.

Warm-up Time 240 hours to meet specification
Operating Temp +5 to +35°C
Temp Coefficient 5E-16/°C
Storage Temp -50°C to +50°C
Magnetic Sensitivity ≤1E-14/Gauss
Pressure 630 to 795 mm Hg
Humidity Up to 80% at 25°C
Size (HxWxD) 27” x 19” x 22” (68x48x56 cm)
Weight 210 lbs (90kg)
Warranty 1 year (2 - 5 year options)
Service Life 15 years

CH1-75 Active Hydrogen PDF DOCUMENT