This is the circuit diagram of powerful AM transmitter which use ceramic resonator/filter of 3.587 MHz. Resonators/filters of other frequencies such as 5.5 MHz, 7 MHz and 10.7 MHz may also be used. Use of different frequency filters/resonators will involve corresponding variation in the value of inductor used in the tank circuit of oscillator connected at the collector of transistor T1.
The AF input for modulation is inserted in series with emitter of transistor T1 (and resistor R4) using a transistor radio type audio driver transformer as shown in the circuit. Modulated RF output is developed across the tank circuit which can be tuned to resonance frequency of the filter/resonator with the help of gang condenser C7. The next two stages formed using low-noise RF transistors BF495 are, in fact, connected in parallel for amplification of modulated signal coupled from collector of transistor T1 to bases of transistors T2 and T3. The combined output from collectors of T2 and T3 is fed to antenna via 100pF capacitor C4.
The powerful AM transmitter circuit can be easily assembled on a general-purpose PCB. The radius/range of this AM transmitter is expected to be one to two kilometers. The circuit operated with 9V regulated power supply to work.
Note: Dotted lined indicates additional connection if a 3-pin filter is used in place.
This is a demonstration about 01A RF Amplifier which is build used old tube component to amplify the signal.
Watch the video: