EXPERIMENTAL STUDY OF QUARTZ CALIBRATOR
The object of research is a calibrator consisting of a quartz oscillator and a diode-based harmonic generator with charge accumulation. The aim of the study is to identify technical parameters and characteristics of the calibrator that are absent in the literature. An experimental study of a quartz calibrator with a frequency grid at 50 MHz has been carried out. The following results are presented: - overrun frequency 20 minutes after switching on; - dependence of the frequency of the first harmonic on the supply voltage; - spectrum of harmonics in the frequency range from 0 to 1500 MHz. A schematic diagram and a brief description of the design are given. A photo and experimental technique are presented. The calibrator is recommended for use in receivers and spectrum analyzers to test their performance and improve tuning accuracy. The following electrical parameters have been achieved: - frequency setting accuracy of the first harmonic ± 2.5 kHz; - power of the first harmonic 0 dBm; - non-uniformity of harmonics in the band from 0 to 1500 MHz no more than 36 dB; - run-out of the frequency of the first harmonic in 20 minutes 34 Hz; - frequency drift of the first harmonic when the supply voltage changes from 5 to 13.5 V, no more than 288 Hz; - the width of the spectral line at the level of minus 40 dB from the maximum is not more than 4 Hz. Comparison of the obtained results with the known ones shows a rather large unevenness of the harmonic power in the frequency range up to 1500 MHz. Reducing the uneven power of harmonics can be achieved in several ways: - supplement the calibrator with a corrector of the amplitude-frequency characteristic; - increase the frequency of the first harmonic. The advantages of this calibrator are the simplicity of the circuit and design, the possibility of repetition in the conditions of serial production, the availability of the element base, ease of adjustment, small weight and dimensions. Using more powerful transistors, it is possible to cover not only the decimeter, but also the centimeter wavelength range.