This is probably the simplest radio transmitter that you will find anywhere. It has a total of five parts and can be constructed into a very small space. It is great for science fair projects or other science related projects where short range transmission is useful. It runs on 1.5 to 3 Volts, with small hearing aid batteries or lithium “coin” cells being ideal. A thermistor or photoresistor can be [...]
Above diagram is a very easy and efficient receiver for actuating garage doors, starter motors, alarms, warning systems and many some other possibilities. The SCR, which has a extremely low trigger current of 30 uA is typical — it demands an input electricity of just 30 uW to activate the relay. A high Q tuned antenna circuit assures rejection of spurious signals. A whip or wire antenna is adequate as [...]
By working with only a small handfull of parts you can assembled this kind of reliable FM Amplifier. It runs with only 1 UHF/VHF type transistor, MFE201. This amplifier will pull in all distant FM stations clearly. The circuit is configured as a common-emitter tuned RF pre-amplifier wired around VHF/UHF transistor MFE201. You will find a couple different models that probably would work too, like the NTE107, 2SC2570, and so [...]
The following is a circuit of a simple AM transmitter. This circuit is available in kit form and can work well. This circuit uses a combination of transistors SA101 and SA103, as the modulation signal amplifier.
