Tuesday, June 14, 2011
1 Watt Four Stage FM Transmitter
1 Watt Four Stage FM TransmitterThis FM transmitter circuit uses four radio abundance stages: a VHF oscillator congenital about transistor BF494 (T1), a preamplifier congenital about transistor BF200 (T2), a disciplinarian congenital about transistor 2N2219 (T3) and a ability amplifier congenital about transistor 2N3866 (T4). A condenser microphone is affiliated at the ascribe of the oscillator.
Working of the 1 Watt transmitter ambit is simple. When you allege abreast the microphone, frequency-modulated signals are acquired at the beneficiary of oscillator transistor T1.
The FM signals are amplified by the VHF preamplifier and the pre-driver stage. You can additionally use transistor 2N5109 in abode of 2N2219. The preamplifier is a acquainted class-A RF amplifier and the disciplinarian is a class-C amplifier. Signals are assuredly fed to the class-C RF ability amplifier, which delivers RF ability to a 50-ohm accumbent dipole or arena even antenna.
Use a heat-sink with transistor 2N3866 for calefaction amusement (Note: or 2N4427 because it works bigger at 12 V and delivers up to 1 watt RF power). Carefully acclimatize trimmer VC1 affiliated beyond L1 to accomplish abundance aural 88-108 MHz. Additionally acclimatize trimmers VC2 through VC7 to get best achievement at best range.
Regulator IC 78C09 provides abiding 9V accumulation to the oscillator, so aberration in the accumulation voltage will not affect the abundance generated. You can additionally use a 12V array to ability the circuit. Assemble the ambit on a accepted purpose PCB. Install the antenna appropriately for best range.
Coils L1 through L5 are fabricated with 20 SWG copper-enameled wire anguish over air-cores accepting 8mm diameter. They accept 4, 6, 6, 5 and 7 turns of wire, respectively.
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