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.
Using a sensor from the time, this circuit was found in the 1992 Radio Electronics Handbook...
This TTL oscillator uses a ceramic resonator as a frequency fixing element. The resonator is found...
The circuit below uses common JFET transistors, which can be the BF245 or MPF102 amplifying video...