JFET Pierce oscillator will test any crystal from 50 kHz through 25-MHz upper frequency limit of fundamental-mode crystals without tuning, and drive counter for measuring crystal frequency, Will test overtone VHF crystals on their fundamental frequency. T1 is small output transformer from tube-type radio, having about 33: 1 turns ratio, or 6. 3-V f
CRYSTAL TESTER - schematic

ilament transformer if 1N645 rectifiers are used in place of 50- F filter capacitors to give fullwave voltage doubler providing required 9 V. RFC1 is 2. 5 mH, and RFC2 is 150-mH miniature toroid. -F. Brown, A Universal Crystal Oscillator, QST, Feb. 1978, p 15-16.

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