This circuit is from the 1990 Motorola Linear Databook, which can be developed with more modern equivalent operating systems. The 1 uF capacitor should be of good quality polyester with small leaks
This transmitter has a range of a few hundred meters depending on site conditions. The coil...
The circuit shown below was obtained from the National Semiconductor Linear Applications Handbook...
This circuit was found in a Popular Electronics from the 90s. The circuit has 4 frequency ranges...