Standardisation and Calibration of Various Equipment by the Use of Standard Frequency Transmissions

Abstract

The standard frequency transmissions are now-a-days widely employed for calibration and standardisation of various equipment. The precision of measurement based on such transmissions is often limited by the stability of the ionospheric propagation characteristics involved. In India, we are now having standard time and frequency broadcast from the National Physical Laboratory, New Delhi at 10 MHz and 15 MHz. By employing both the transmissions, it may be possible to reduce the error due to ionospheric changes and to obtain standards of frequency at 2.5 MHz and 12.5 MHz without involving a precision local oscillator in the receiving system. The system is also capable of measuring the precision of an oscillator at 12.5 MHz in case where the ionospheric error may be neglected. A set up for studying the differential ionospheric shift between 10 MHz and 15 MHz without involving a precision local oscillator has been suggested and a theoretical estimate of the differential shift is also made. Improvement of preci...