I am trying to build a simple AM transmitter, transmitting only a carrier wave and thus silencing the noise on my radio standing next to my circuit.
I built this circuit on a breadboard.
It's a simple positive square wave oscillator designed to produce a frequency between 618kHz and 1934kHz, roughly the range of my radio. When simulating, this indeed produces the square wave intended.
At the output of my oscillator I simply put a wire on my breadboard acting as an antenna.
This however doesn't influence the audio coming from the receiver in any way.
What did I do wrong?
Update: It is not per se my intention to just jam a nearby radio. I try to get this circuit or something similar to work, as an early step in establishing a solid understanding about RF-communication. I try to radiate something controlled at a variable frequency. Just a carrier wave and thus silence seems the simplest to do.
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Best Answer
The minimum recommended supply is 10 volts between positive supply pin and negative supply pin. You are using 5 volts according to your circuit.
Also, to make an effective monopole antenna you will need a ground connection or at least a few hundred pF capacitance to real ground.
Check that the circuit oscillates using an oscilloscope. I doubt that it will with a TL072 and a 5 volt supply. Be also aware that when you do get it working you might really annoy neighbours who are listening to their radio and you might contravene local laws on illegal radio transmission. I would suggest you use a ferrite rod and coil as you transmitter antenna as this has very poor penetration range due to it only producing a magnetic field and not a full-blown EM field.