Seiler Oscillator

This article will describe a transistorized vfo to cover the amateur high frequency bands from 3.5 to 30 mhz* it is designed to drive small transmitters such as the DX-40, which have provisions for vfo input and i 15 vac output for a tr switch. Construction details and sources for obtaining parts are given to aid the home-brewers.

Circuit Details

Fig. 1 shows the oscillator circuit. This is a Seiler oscillator using the popular MPF-1 02. This transistor lias a minimum effect on the frequency of the tuned circuit. The tuned circuit, however, will change frequency with temperature. In breadboarding experiments with this circuit, soldering really caused frustration. If the temperature of the shack in the morning was about 50 degrees, after turning on the heater and the oscillator, the frequency would gradually drift as the room

MPf-102

TOflOl 0 COIL

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