Electronic projects


you are here: home page :: projects :: Radio :: transmitters :: AM Transmitter

AM Transmitter

Circuit diagram

Notes:
It is illegal to operate a radio transmitter without a license in most countries. This ircuit is deliberately limited in power output but will provide amplitude modulation (AM) of voice over the medium wave band.
The circuit is in two halfs, an audio amplifier and an RF oscillator. The oscillator is built around Q1 and associated components. The tank circuit L1 and VC1 is tunable from about 500kHz to 1600KHz. These components can be used from an old MW radio, if available. Q1 needs regenerative feedback to oscillate and this is achieved by connecting the base and collector of Q1 to opposite ends of the tank circuit. The 1nF capacitor C7, couples signals from the base to the top of L1, and C2, 100pF ensures that the oscillation is passed from collector, to the emitter, and via the internal base emitter resistance of the transistor, back to the base again. Resistor R2 has an important role in this circuit. It ensures that the oscillation will not be shunted to ground via the very low internal emitter resistance, re of Q1, and also increases the input impedance so that the modulation signal will not be shunted. Oscillation frequency is adjusted with VC1.
Q2 is wired as a common emitter amplifier, C5 decoupling the emitter resistor and realising full gain of this stage. The microphone is an electret condenser mic and the amount of AM modulation is adjusted with the 4.7k preset resistor P1.
An antenna is not needed, but 30cm of wire may be used at the collector to increase transmitter range.

author: Andy Collinson
e-mail:
web site: http://www.zen22142.zen.co.uk
project categories:
folder Audio (49)
folder Power & high voltage (43)
folder Radio (23)
folder Light & LED (31)
folder Tools & measurement (40)
folder Telephone (18)
folder Automotive (10)
folder Microcontrollers (12)
folder Sensors & control (47)
folder Timers & oscillators (40)
folder Miscellaneous (26)

StumbleUpon button

Share this page
Bookmark and Share
project subcategories:
All subcategories
receivers & field meters
transmitters
amplifiers
other

similar projects:
15W Fm-transmitter
2 Transistor FM Voice Transmitter
3W FM Transmitter
4W FM Transmitter
A small FM transmitter (SMD)
AM FM Simultaneous Transmitter Using Digital IC
AM To FM converter
FM Telephone Bug
FM Transmitter Bug
Medium range transmitter

recently added projects:
Doorbell for the Deaf
High Quality Intercom
Combinational Conjuring Trick
POT-PLANT POWER
Ultrasonic Dog Whistle
Quiz Circuit
LED Torch
Insect Repellant
Speaker Microphone Circuit
Magic Wand Conjuring Trick.

most popular projects:
Led display digital Voltmeter
500W low cost 12V to 220V inverter
Low pass filter - Subwoofer
Metal Detector
High And Low Voltage Cut Off With Time Delay
Basic UPS Power Supply
2N3055 Power Amplifier
200W audio amplifier
LED Torch
100W RMS Amplifier


DIY Electronics Projects

Promote Your Page Too