AM mini transmitter module

This is a colpitts circuit that works in the AM band,that operates in 1.1 Mhz , which is received for any radio.It's very simple and small. All the conmponents are  easily available in the market. You can put at  the exit of a mic with preamplifier or an oscillator connecting to Vin.  The range is nearly 328 feets with a good antenna and a usual 9 volt pile.  The inductor is the typical choke of 10uH and is very easy of to obtain.

 

The measures of the board are 1.7 ich x 0.7 inch                                                                        
Nevertheless if you can build it, with fifty turn of wire in a form  of 0.2 inch of ferrite, you can add an variable capacitor and modify the frequency but that is another story.

 


Be careful because depending of your country you should have license for to operate with this circuit. I don't assume any responsability.









List of components.

Resistors

a resistor of 47k Ohms (1/4 o 1/8w)

a resistor of 200 Ohms (1/4 o 1/8w)

a BC547 transistor

2 ceramic capacitor of 1nf (for 16v)

a ceramic capacitor of 4.7nf (for 16v)

a ceramic capacitor of 10nf (for 16v)

a electrolytic capacitor of 47uF (for 16v)

a pcb terminal for 3 poles

a antenna.



Finally, checking the circuit

If the circuit is built as of the figures have shown there oughtn't any trouble.Turn on the circuit and put your radio in the AM band. When you are near of the1.1 Mhz in your radio you should hear a whistle and this mean that the circuit works. For this first adjusting you should put the circuit some feets of your radio.To Find and find out which is the best position in your radio for to listen
your tranmitter.If all goes well you can add an oscillator or a microphone with a preamplifier at the entrance, Now you are ready to discover the range of your emitter.

Simple oscillator with one relay.

There is a small circuit for to generate a frecuency of 5khz. All that you need is a relay and a voltage source, the values are not critical and adding in paralell a capacitor you can modify the frecuency. The applications of this circuits are several, in oscillator, timers, rings, etc.

Astable multivibrator using relays.

Here is a unusual astable circuit using just relays without transistors or valves. It's very rude and funny but it works. You can modify the frecuency with the variable resistor P1 between certain limits and alterate the wide of the pulse with P2. But be careful because if you get at the limits of the resistors the circuit don't works and you should to reset the circuit by turn the resistors and put off the source and before to start again!. As in another circuits you can modify the value of the capacitor and to experiment with several relays. But the best work is with the 3300uF capacitor, with relays of 50-300 ohms and sources of 5 volts to 12 volts depending of the types of relays that you use, This circuit can be used like warning-light, encoder, alarms, clock, etc.