The resistors R1 and R2 consist of 8 220 ohms x 2 W resistors connected in parallel. The dissipation must be higher for high transmitter power. The indicator can be the multimeter.
The coil of this receiver determines the range. It can have 2 to 10 turns of wire 20 to 24 in the...
This circuit has tone control, and its power depends on the supply voltage. The circuit is from...
This circuit with 10 MHz and 1.25 MHz TTL outputs was found in an American documentation from the...