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Friday, October 8, 2010

Simple AM Radio Circuit using Transistor

This is a circuit diagram AM transmitter, where the AM transmitter using ceramic resonator / filter of 3.587 MHz is presented here. This circuit is based on the core to the operation of the transistor circuits. Resonators / filters such as the frequency of 5.5 MHz, 7 MHz and 10.7 MHz may also be used.

Using a different frequency filters / resonators will involve corresponding variation in the value of inductor used in the oscillator tank circuit is connected to the collector of transistor T1. AF input for modulation is inserted in series with the emitter of transistor T1 (and resistor R4) using a transistor radio type audio transformer such as a driver on the circuit. In the picture above the modulated RF output is developed across the tank circuit which can be tuned to the resonance frequency of the filter / resonator with the help of gang condenser C7. Next two stages formed with low-noise RF transistors BF495 is, in fact, connected in parallel for amplification of modulated signal coupled from collector of transistor T1 to the base of the transistors T2 and T3. Combined output from the collector of T2 and T3 is to the antenna feed through 100pF capacitor C4. Circuits that can be easily collected in the general-purpose PCB. Range from transmitter is expected to be one to two kilometers. Circuits that require regulated 9 volt power supply for operation.