This amplifier for the 10 m (30 MHz) band has a gain of 12 to 15 dB having been found in an American documentation. Other RF transistors can be used like 2N2222 or 2N2218.
We find this microphone voice effect in 1992 documentation. The vibration of the relay contacts...
This circuit for the car uses LDRs as sensors and does not need to be connected to the lamp. The...
Found in a Popular Electronics from the 90s, this circuit can be made with current equivalent...