This Hughes circuit is from 1968. Equivalent modern components can be used. The input impedance is 1000 M ohm.
This circuit was found in the January 1996 issue of Electronics Now magazine. The circuit is...
This circuit was found in a 1987 edition of the United States' Hands-On Electronics magazine. The...
This circuit is from the magazine 73, for radio amateurs, from the 80s. The circuit uses common...