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Old 17th Feb 2009, 12:21 pm   #5
jim_jobe
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Join Date: Nov 2004
Location: Ripon, N.Yorkshire, UK.
Posts: 782
Default Re: Measuring Resonant Frequency

By coincidence I was reading this article last night. It's "Suggested Circuit No. 224" by G.A.French in RC July 1969. If you substitute your LC circuit in place of "inductor" and the 620pF capacitor it should indicate resonance for you. TR1 can be any high gain silicon tranny and D2 any silicon diode, 1N4148,etc.R1 should be chosen to give a collector current of about 4 to 5 mA and R4 selected to limit the meter current to 100uA. Resonance will be seen as a pronounced dip in the current.
Jim
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