A experimental crystal frequency transmitter ----- Crystal FM Transmitter

Experimental crystal frequency transmitter, Crystal FM Transmitter Keywords: FM launch, frequency modulation circuit, crystal frequency frequency Many radio enthusiasts want to make a FM transmitter, especially in the frequency band band band of 87 to 108MHz, which can be received by the ready-made FM radio, which is favored by everyone. In many publications, an example of the frequency modulation transmitter is introduced, but most of the capacitors three-point circuits and Caratus oscillation circuits are used. This circuit is simple, but its frequency stability is not high, especially under amateur conditions, a slightly moving circuit board or antenna position, and the frequency changes. This author describes a radio transmitter with a crystal cell. Circuit principle As shown in FIG. 1, a first-stage audio amplifying circuit is formed by a V1 and associated blocking elements, providing a sufficient intensity audio signal to the modulation level. D1 is a variation of a variable voltage variable as the opposite voltage added by the two poles, thereby changing the center frequency of the oscillator of the crystal and the peripheral circuit to achieve the frequency modulation purpose. The signal output by the oscillator is enlarged by V3 frequency, and then the matching transformer completes the match and the filter output. The circuit uses a tuning transformer, so it is adjusted after the production is completed, and it matches it. The method is to make a simple field strong circuit (as shown in Figure 2), which is connected to the output of the transformer, adjust the magnetic core until the current table indicates the maximum. The components used in the circuit are used as much as possible to use high-frequency characteristics. The crystal oscillator is selected from 29 to 36 MHz, D1 can be used by MV2105, and the transformer needs to be self-made, and it is possible to select a television as well as the skeleton, remove the shield, the enamel line of 0.2mm, the primary wrap of 3 on the skeleton, times Around 1. The antenna can use 1/4 wavelength soft wire distribution.

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