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Saturday, January 31, 2009

preamplifier 88-108Mhz

This VHF amplifier working on Band 2 Radio Spectrum tuning approximately 88 - 108 Mhz
The Preamplifier circuit uses two 2N3819 FET's in cascade configuration. The lower FET operates in common source mode, while the upper FET, operates in common gate, realizing full high frequency gain. The bottom FET is tunable allowing a peak for a particular station.

Coil details follow:
L1 4 turns of 18swg air spaced with a 1cm diameter, the tap is one turn up from earth end...
L2 4 turns of 18swg air spaced with 1 cm diameter. The coupling coil is 1 turn interwound from the supply end. Enamel coated wire must be used. More info ...