Mosquitoes, annoying when only rural residents Yes tourists, in recent years began to seriously disturb and citizens. Multiplying in damp basements almost year-round - the good, the setting is almost perfect - they then settled on apartments even multi-storey buildings. Conventional means of fighting off different kinds of chemical substances is of little help.
In recent times, the market appeared different ultrasonic tweeters that, if you believe the advertising that can keep mosquitoes at a respectful distance. But whether our mosquitoes differ from, say, Singapore, or the frequency of the radiated signal is not the same, or something like that, but to the question: "Does that help?", experienced answer this novelty rather strangely...
The device described here, a schematic diagram of which is shown in Fig.1, will allow everyone to be on this account their own opinion. The master oscillator is assembled on the inverter DD1.1 and DD1.2 CMOS chips K561LN2. Other elements of this chip, form the base currents of transistors VT1 - VT4, alternately through transistors VT1 and VT4 or via VT2 and VT3, connecting the emitter of BA1 to the power source.
Fig.1
Powerful transistors operate in the switching mode eve special heat sinks especially do not need, but in severe temperature conditions and they can be required.
Diode VD1 - any germanium. Possible placement of elements on the printed circuit Board shown in Fig. 2. Metalogenia sections of foil under the transistors perform the role of a kind of sinks. Variable resistor R3 can be any type, for example, SDR-4 group A.
Fig. 2
Dynamic head of BA1 - high-frequency power of 3-4 W with a voice coil impedance of at least 4 Ohms, for example, 6ГLW-4. Although the passport of the higher frequency radiation such "Squeaker" is a small, experience shows that they are able to radiate and oscillations of ultra high frequency-up to 40... 50 kHz and above.
The desired radiation frequency set by the variable resistor R3. It can be equipped with pre-graduated on the oscilloscope scale. When specified on the diagram the values of resistors R2, R3 and capacitor C1 generator covers the frequency range of 60 16... kHz. But this is its basic frequency. Since the shape of the electrical signal generator is far from sinusoidal, acoustic spectrum (with sufficient bandwidth dynamic head) may appear and harmonics of this fundamental tone that will not be the fault of the device - to frighten, to scare...
The power source of the device (voltage 4.5...6 In) should be able to give current
Mosquitoes - annoying bloodsuckers, and distributors of a number of diseases (malaria, yellow fever, etc.) is not the only possible object of research with the help of the device described here. Biting midges, Midge (them says more than a thousand vectors of anthrax, glanders, tularemia, plague, leprosy), and a poplar moth, cockroaches, weevils, carpet beetle and other animals, somehow intruding in our lives, the layout also be vulnerable to such impact on her. It remains to check... And maybe to start a new direction in the work of radio Amateurs. The direction in which the experiments of this scale only large group of people that owns electronic appliances
Author: Yu. Vinogradov, Moscow; Publication: N. Bolshakov, rf.atnn.ru