VLF_CONVERTER

Published:2009/7/10 0:45:00 Author:May | From:SeekIC

The VLF Converter can be used to pick up signals for the general coverage of shortwave receivers. A number of unusual signals can be heard on frequencies below 15 kHz.This converter wiil convert frequencies from 0 to 250 kHz to 3500 to 3750 kHz so that the LF- and VLF-band segments can be received on an amateur or shortwave receiver that covers 3 500 to 4000 kHz.Signals from a short whip antenna (8 to 10 feet) are coupled through low-pass filter L1/L2/C2/C3 to RF amp Q1. Q3 mixes these signals with a 3.5-MHz signal from Q2 and associated components C4, R5, R4, and 3.5-MHz XTAL. L3 is an RF choke that presents an inductive load to Q3. It should be resonant some-what above 3.5 MHz when placed in the circuit. An adjustable coil of about 30 to 100 μH should be suffi-cient. The converter output is taken from the emitter of Q3 through C6.



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