Coaxial cable - inductor. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Knots of amateur radio equipment. Generators, heterodynes
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Coaxial resonators are widely used in the ultrashort wave bands. At KB, the dimensions of such resonators (even relatively small ones - the so-called spiral ones) reach values \uXNUMXb\uXNUMXbthat are not acceptable for practice.
Meanwhile, segments of coaxial cables can be successfully used in generators instead of an inductor, and the quality factor and temperature stability of such a "coil" will be quite high. If it is made from a modern thin cable, then even in the short wave range such a "coil" will take up little space: the cable can be twisted into a small bay.
The figure shows the adjustable oscillator of the frequency synthesizer of a connected KB radio station. It is assembled on a V3 field-effect transistor according to the "capacitive three-point" scheme. The role of the "coil" of inductance L1 is performed here by a short-circuited piece of coaxial cable. With the values of the elements indicated on the diagram and a cable length of 25 cm, the operating frequency of the generator is 50 MHz (to be transferred to the operating frequency range, it is further divided by digital microcircuits by 10).
The frequency of the generator can be changed by a conventional variable capacitor or varicaps, as is done in the described generator.
The generator can be made on a transistor of the KP302 series (selection of resistor R2 is required). The type of varicaps used depends on the requirements for the frequency range covered by the generator.
Literature
- QST (USA), No. 5 1981
Publication: N. Bolshakov, rf.atnn.ru
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