High stability of output frequency with changes of the supply voltage is achieved by using resistors with large resistance in the source circuits of both stages and the use of large DC capacitors in circuits the gate and drain of the generator of the cascade. Even if you change the supply voltage from 3 to 9 In the output frequency takes no more than 1 Hz from the nominal value of 1 MHz.
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By itself, the circuit is so stable that the characteristics of the generator as a whole is determined only by the quality of the quartz resonator. High quality ovenized quartz crystal after heating provides instability 10-8 per day. With sufficient constancy of ambient temperature the overall scheme provides a similar stability.
Good agreement with IP TTL is achieved via a Schmitt trigger, for example type 7413. Input 2.2 kω resistor creates an offset of the Schmitt trigger within the hysteresis, not overly burdening source follower generator. Schmitt trigger type 7413 generates the signal level enough to run the TTL of IP, even in the case where the supply voltage of the generator is reduced to 3 V.
The output signal of the Schmitt trigger is rich in high frequency harmonics and therefore can be mixed with the signal of standard frequency 10 MHz, which is transmitted via the broadcasting network of the National Bureau of standards, allowing you to tune the oscillator with an accuracy of 0.1 Hz relative to the nominal frequency. Using this method of measurement is possible with sufficient accuracy to determine the daily short-term and long-term stability. In this case, the generator can be used as a secondary frequency standard, to check the standard of National Bureau of standards.
The DM capacitor is the range of the calibration, which is performed by means of the trimmer. The capacity of DM can vary depending on the type of quartz resonator.
Author: King, Firm Oroco Communications Inc. (Middletown, NY); Publication: N. Bolshakov, rf.atnn.ru