In fact, it is only a simple Clapp Oscillator with the output directly driven into a few meters of wire. The transmitting frequency depends on the used crystal. This may be any crystal between 1 and 15 MHz, higher frequencies may perhaps work also, therefore you may lower the 2 capacitors a little bit.
The transmitting frequency is not only the one shown on the crystal, but also “harmonics”: If you have for example a crystal of 3.56 MHz, then it transmits (of course) on 3.56 MHz, but also a bit at 7.12 MHz (2 * 3.56), 10.68 MHz (3 * 3.56), 14.24 MHz (4 * 3.56), etc.
The operating voltage is not critical, a 9 volt battery will do the job.
- C1 – 100 picofarad
- C2 – 100 picofarad
- R1 – 10 kilo-ohm
- R2 – 1 kilo-ohm
- S1 – Morse key or switch
- T1 – BC547 or any other universal NPN transistor
- X1 – Any crystal you like between 1-15 MHz