The CH1-81 Rb Frequency Standard is used to keep time and frequency units, to measure high-stability time and frequency parameters, to verify and certify various types of high-stability crystal oscillators.

The CH1-81 Rubidium Frequency Standard has six options: CH1-81, CH1-81/1–CH1-81/5.

The Standards can be supplied as a separate module with a 27 Vdc power supply in a standard case with a built-in time scale former providing time scale signal outputs.

The Instrument principle of operation is based on a crystal oscillator frequency stabilization to the electromagnetic energy absorption frequency during RB87 atoms transition from one energy state to another.

The high stability of the standard output signal is defined by the frequency stability of the atomic transition used.


Output: 5 MHz, 1±0.2 V rms into 50 Ohm

Frequency stability:

Measurement time


1 s


10 s


100 s


Temperature coefficient of frequency: 1.2.10–12/ °C

Frequency tuning range (by a magnetic field): 1.5.10–9

Drift per day: 1.10–12 (CH1-81, CH1-81/2/4), 3.10–12 (CH1-81/1/3/5)

Phase Noise

Offset from carrier

SSB phase noise, dB/Hz

85 Hz


1 kHz


10 kHz


Frequency drift in operating temperature range: not more than 1.2.10–10


Operating temperature range: –40–+55 °C

Power: 22–30 V dc

Power consumption:

warm-up: <80 W

operating mode at 25 °C: 18–21 W

Dimensions, mm; weight, kg:

358x167x82; 3.5 (CH1-81, CH1-81/1)

459x188x129; 6.0 (CH1-81/2/3)

459x188x129; 6.5 (CH1-81/4/5)