We found this circuit in the January 1992 issue of Radio Electronics magazine. The circuit consists of an automatic gain control.
The configuration below is suggested by the National Semiconductor Linear Applications Handbook. The...
This circuit is from Popular Electronics from October 0, 1981. The diodes can also be 1N4004 and...
Of course, the range of this transmitter found in a 1992 documentation is not exactly 4 km, as it...