[eagle] Source of 70 cm Microphoncs Found

Juan Rivera juan-rivera at sbcglobal.net
Sat Jul 14 11:18:24 PDT 2007


John,

The microphonics is caused by C19, C27 and C28 (.047uF 25V) and C50 and C51
(.022uF 25V).

I found the best way to isolate this is to inject a CW signal into the
receiver, tune the signal in at the IF output using my TS-2000 in AM mode,
and then listen to the audio output while lightly tapping each component one
at a time.

According to my research, barium titanate, the base ceramic material for
most ceramic SMD capacitors is inherently microphonic.

Juan






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