Wideband VHF preamplifier

Published:2012/10/11 21:11:00 Author:muriel | Keyword: Wideband, VHF, preamplifier | From:SeekIC

This inexpensive VHF preamplifier uses the BF324 TO92 style pnp transistor in a grounded-base configuration. The circuit may be used as a signal booster with VHF receivers whose front end suffers from low sensitivity (such as many valved and army surplus types). The frequency range of the preamplifier is roughly from 75MHz to 150MHz. The two inductors in the circuit are home made. L1 consists of 10turns of 24SWG enamelled copper wire; the internal diameter is 3mm, no core. Inductor L2 has 13 turns of the same wire, and an internal diameter of 5mm; no core is used either. A construction tip: close-wind the inductors using 3 and 5mm drill bits respectively as temporary formers. The prototype of the preamplifier was successfully used with an 88-108 MHz FM broadcast receiver and a 2-metre VHF ham receiver. The preamplifier draws about 2.5mA from a 5-volt supply. Wideband VHF preamplifier circuit schematic



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