Schematics > RF circuit > Powerful AM transmitter
Powerful AM transmitter
The circuit for a powerful AM transmitter using ceramic resonator/filter of
3.587 MHz is presented here. 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 circuit can be easily assembled on a general-purpose PCB. The range of the
transmitter is expected to be one to two kilometers. The circuit requires
regulated 9-volt power supply for its operation. Note: Dotted lined indicates
additional connection if a 3-pin filter is used in place.
Title: Powerful AM transmitter
Source: www.electronic-circuits-diagrams.com
Published on: 2005-02-09
Reads: 665
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