This circuit can generate signals of different frequencies, switched by a DC voltage. The frequencies are determined by the crystals. The circuit is from a 90s American documentation.
This low noise preamplifier has a gain of 19 dB in the 30 MHz band. The circuit is from the 80s....
The shock is 2.5mH for frequencies between 3 and 30MHz. C is 1nF, R is 47k and the transistor can...
This traditional doubler configuration with the 555 can be found in other articles on the author’s site....