SIX_RANGE_RF

Published:2009/7/21 2:04:00 Author:Jessie | From:SeekIC

Covers from 100 kHz to about 75 MHz in six bands, for checking low-frequency IF circuits on up to VHF circuits (using harmonics up to 220 MHz). Omission of frequency read-out dial scale simplifies design without affecting usefulness for troubleshooting. FETs can be HEP-802 or MPF102, and output transistor is 2N3866 or 2N706, First FET is Hartley oscillator lightly coupled through 5-pF capacitor to FET source-follower isolation stage. Last stage boosts signal level up to about 1 V on most bands. Tuning capacitor is broadcast-band type having 300-pF AM section and 25-pF FM section. Set of six coils can be purchased as Conar CO-69 through CO-74 from National Radio Institute or can be wound as suggested in article to give high-end band limits of 0.57, 1.4, 4.5, 17, 39, and 75-80 MHz. For portable use, 12-V battery pack or 9-V transistor radio battery can be used to give constant 9-V supply.-Brew Up a Signal Generator, 73Magazine, Jan. 1978, p 50-52.



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