Hobby diy
Cardiophone
The human heartbeat can be made audible by using this cardiophone circuit. It is basically an audio circuit coupled to a probe made specially for the purpose of picking up electric signal from the human heart.
To get the best signal, place the probe’s electrodes to a point close to the heart. The preferred point is [...]
74F13 mini bug transmitter
Take a look at this mini transmitter which can be used as a bug transmitter or for spy transmitter too. It uses a single IC 74F13, one coil, a capacitor, one trimmer, one resistor and ofcourse one electret mic. It is so easy to build and can give you a total coverage range of about [...]
Foxhunt transmitter
This 2 meter 144 MHz transmitter is used in amateur competitions where a hidden transmitter is to be “hunted” using mostly homebrewed receivers and antennas. The featured electronic circuit is the transmitter. It radiates a high quality signal without unwanted harmonics. Transistor T1 and the crystal togheter make the oscillator that generates a 36MHz signal.
The [...]
