This circuit covers 400 kHz to 40 MHz in three bands according to the selected coil. The double MOSFET allows equivalent, since the original is not easy to obtain.
With a 1 500 uFcapacitor this timer can reach times up to one hour. The capacitor must be of good...
We found this circuit in a 1975 filter cookbook. The circuit can use other operational amplifiers and...
This circuit is from an Italian publication from 1988 but can still be easily assembled....