Circuit knowledge

This affordable FM radio receiver antenna enhancer makes use of the BF324 TO92 type pnp transistor in a grounded-base arrangement.
The circuit can be utilized like a signal booster with VHF receivers whose front end is afflicted with reduced level of sensitivity (like a lot of valved and army supplemental variations). The frequency selection of the preamplifier is approximately from 75MHz to 150MHz.

The 2 inductors in the circuit are do-it-yourself. L1 includes 10 turns of 24SWG enameled copper wire; the inner dimension is 3mm, without any core. Inductor L2 bears 13 flips of the identical wire, as well as an inner diameter of 5mm; without core as above. A building tip: tight-wind the inductors making use of three and 5mm drill bits respectively in the form of momentary cores.

The prototype of the preamplifier was effectively tried with an 88-108 MHz FM broadcast receiver along with a 2-metre VHF ham receiver. The preamplifier consumes around 2.5mA from a 5-volt supply.