This circuit was found in a 1993 Electronics Hobbyst Handbook. The circuit operates in the FM range. The coil has 4 turns of 24 or 26 wire in a coreless form 0.5 cm diameter.
In the figure we have an inductance bridge for values between 1 and 30 uH at a frequency of 5 MHz....
We found this circuit in the Motorola Linear Databook published in 1990. The circuit can be...
Using a varactor or varicap, this 1969 Electronics World circuit has a modulation range from 75...