This circuit is from the 1968 ARLL documentation. The MOSFET admits equivalent and the coil determines the operating frequency range being the plug type.
This frequency band below 15 kHz converter was found in a Popular Electronics from the 90's. The...
The frequency of a 555 oscillator depends on the capacitance of capacitor C. We can take advantage of...
This circuit applies to other operational ones, other than the one indicated. The formulas next to the...