This circuit for the 3 to 6 MHz band was found in a 90s Popular Electronics. The components of the network formed by C6 depend on the frequency range to be covered.
This circuit was obtained in an Electronics World of 1969. It is a crystal oscillator with a 100...
This circuit, shown in the figure, consists of a variable gain amplifier with differential input...
This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made...