Introduction

Only a three companies in the world that I know of make Hydrogen Maser frequency standards. One of the two Russian manufacturers is KVARZ and below is their CH1-76 passive H-maser. Passive masers lock an OCXO to the 1420 MHz hydrogen resonance peak rather than detecting the signal directly as do active masers. Passive masers are generally smaller and cheaper than active masers but active masers have slightly better performance.

Performance

Below is the measured performance of a CH1-76 (using a CH1-75 active maser as the reference). Stability values to note are 1E-13 at 10 seconds, well under 1E-14 at an hour, and a noise floor near 4E-15 at one day.

AHM (CH1-75) vs. PHM (CH1-76) after about 600,000 seconds (one week)