This circuit for medium and short wave range was found in an American documentation from 1992. The circuit can use general purpose transistors and the antenna can be external or telescopic.
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals...