The L1 coil is formed by 4 turns of wire 20 in the form of 0.5 to 0.6 cm without core. The circuit is from an 80's documentation. The range reaches a few tens of meters.
This is the power supply indicated for the previous circuit (CB18905E) providing a voltage of 24 V...
This simple 1-transistor reflex receiver was published in Radio Electronics magazine in September 1959....
In this Radio Electronics from May 1958 we have the now common use of the varicap in a frequency...