In search of ultrasound, providing a deterring effect on animals of a species, often build generators, or otherwise varying the frequency of the radiation. A schematic diagram of one of these generators is shown in the figure.
On the elements DD1.3, DD1.4, R5, R7, C5, C6 assembled symmetrical multivibrator whose frequency can be changed in the range of 25 to 50 kHz. On the emitter followers (transistors VT2-VT5) assembled power amplifier, the output of which is connected the emitter - high-frequency dynamic head of BA1.
The excitation frequency of the multivibrator depends not only on the values of its resistors and capacitors F=1/(R5·C6+R7·C5)), but also on the state of the transistor VT1. The excitation frequency is minimal, if this the transistor is closed, maximal, if open; it increases from the minimum to maximum opening VT1.
The mode of operation of the transistor VT1 changed periodically. This period depends on a constant R2C1 T=2R2·Cl) specifying the frequency of excitation of the generator is performed on the elements DD1.1 and DD1.2, and a constant R3C2, which converts the square wave output voltage of the generator in the "trapezoidal" the current in the base of the transistor VT1.
Thus modulated by a high frequency generator will emit ultrasonic vibrations in the frequency range of 25 to 50 kHz, running his "there and back" for 1/6 1/9... S.
Believing that rodents can get used to this orderly radiation, the author proposes another method of scanning the ultrasonic range - three inmunizaciones generators rassoglasovanii frequencies (Fig. 144).
The device can be used type resistors MLT-0,125. Capacitors C1-NW, C5 and C6 - any ceramic, C4 - any oxide. Diodes VD1-VD3 - silicon pulse or high frequency. Transistor VT1 is any of KT315. Composite transistors VT2 and VT4 can be any of CT or CT, a VT3 and VT5 - from CT or CT.
Dynamic head of BA1 - small ЗГLW-1 or 6ГLW-4. May be suitable and other high-frequency tweeters, but in any case the resistance of the head BA1 must be at least 4 Ohms.
When the voltage of the power source 9 and an 8 Ohm load, the current drawn by the device, does not exceed 0.5 A.
The device may be required to clarify the range of frequencies and ultrasonic frequencies infrastkuturnykh generators. This can be done by oscilloscope or by listening, pre-vailing in 5-6 times the ultrasonic frequency of the multivibrator is connecting, for example, parallel to the capacitors C5 and C6 capacitors of 1000 pF.
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