FREQUENCY_STANDARD

Published:2009/7/21 1:54:00 Author:Jessie | From:SeekIC

Uses high-performance TTL ICs operating from regulated 5-V supply furnishing 260 mA, connected to point X. Provides choice of 18 precision frequencies if all ICs are used, or 8 marker frequencies if only upper three ICs are used. Adjustable level control permits matching output of frequency calibrator to incoming signals such as from WWV, or turning full on for strong, clear markers.HEP715 oscillator transistor is coupled to TTL by HEP50 transistor. 7493 binary dividers U1 and U5 divide by factor of 2, with 7490 decade dividers making up remainder of logic. Reset pins 2 and 3 control operation of logic, either with S1 or with progressively shorted contacts of rotary switch S2. Crystal should be ordered for 0.0005% tolerance, F-700 or SP7.P holder, 32-pF load, and 4 MHz at room temperature.-B. Kelley, Universal Frequency Standard, Ham Radio, Feb. 1974, p 40-47.



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