AM transmitter for the 10 meter band (28MHz) - In this project, you will make a simple 3-stage low-power broadcast-type
circuit, using a crystal oscillator integrated circuit and an a collector modulated AM oscillator with amplifier.
You can connect the circuit to the an electred microphone or amplified dynamic microphone. Using an electred
microphone is shown (in gray) in the diagram below. (no amplified dynamic microphone has a to low output voltage
to work. at least 100mv is needed). You could also add a LF preamp stage of one transistor to allow connecting a
dynamic microphone directly. You'll see that you can receive the signal through the air with almost any AM radio
receiver. Although the circuits used in radio stations for AM receiving are far more complicated, this
nevertheless gives a basic idea of the concept behind a principle transmitter. Plus it is a lot of fun when you
actually have it working! Remember that transmitting on the 10 meter band you'll need a valid radioamateur
license!!. . . [by Guy Roels ON6MU]
1 Watt Class-C Amplifier - schematic only, no circuit description. . . [Charles Wenzel (unless
1 Watt Four Stage FM
Transmitter - This FM transmitter
circuit uses four radio frequency stages: a VHF oscillator built around transistor BF494 (T1) , a preamplifier
built around transistor BF200 (T2) , a driver built around transistor 2N2219 (T3) and a power amplifier built
around transistor 2N3866 (T4). A condenser microphone is connected at the input of the oscillator. . . .
1 Watt Morse Transmitter - Schematic only, no circuit description included. . . [CircuitoZ.net,
1 Watt RF Amplifier - This is a universal 1 Watt RF class C amplifier that is ideally suited
for low power FM transmitters. Input should be at least 100mW to achieve 1W output. It is recommended to enclose
the amplifier in a metal case. . . . [Designer's name not included]
1.3W VHF RF Amplifier 2SC1970
88-108 MHz - This RF power amplifier is
based on the transistor 2SC1970 and 2N4427. The output power is about 1. 3W and the input driving power is
30-50mW. It will still get your RF signal quit far and I advice you to use a good 50 ohm resistor as dummy load.
To tune this amplifier you can either use a power meter/wattmeter, SWR unit or you can do using a RF field meter.
. . . [Designer's name not included]
1.5 volt FM
transmitter - Schematic only, no
circuit description included. . . [designer not identified]
1.5 volt tracking transmitter - Schematic only, circuit description not included. . . [Andy Wilson's
1.5V Battery operated FM reBroadcast
transmitter - This implementation is
adapted to rebroadcast the output of a CD player, television receiver, or radio receiver. I use it so that I can
move about the house and listen to my favorite programs without disturbing others. Within and the house. . .
[Contents ©2002, 2003 Richard Cappels All Rights Reserved]
1.5V Tracking Transmitter (with Video
Clip) - The current draw for this
tracker is 3.7mA, so the 1. 5V button cell will last awhile. What the heck am I suppose to hear you ask? When
your circuit is working you should see the LED flash quite fast. Take your FM radio and search for the low-beat 'humbe-humbe-humbe-etc'
equal to the flash of the LED (Tony van Roon's probably around the 100Mhz). Found it? If that position is
interferering with a radio station. . . [Tony van Roon's circuit]
Amplifier - Circuit Schematic only. .
. [Designer's name not included]