[eagle] Re: Source of 70 cm Microphoncs Found

John B. Stephensen kd6ozh at comcast.net
Sat Jul 14 14:57:15 PDT 2007

This is what we suspected earlier but couldn't prove. Those capacitors, plus 
C54, need to be replaced with film capacitors similar to C23, C24, C52 and 



----- Original Message ----- 
From: "Juan Rivera" <juan-rivera at sbcglobal.net>
To: "John B. Stephensen" <kd6ozh at comcast.net>
Cc: <eagle at amsat.org>; "Bill Ress" <bill at hsmicrowave.com>; "Dave Black 
(Home)" <dblack1054 at yahoo.com>; "Dave Black (Work)" 
<dblack at mail.arc.nasa.gov>; "Dave hartzell" <hartzell at gmail.com>; "David 
Smith" <w6te at msn.com>; "Don Ferguson" <kd6ire at sbcglobal.net>; "Juan. Rivera 
(Home)" <juan-rivera at sbcglobal.net>; "Juan.Rivera (Work)" 
<Juan.Rivera at gd-ais.com>; "Samsonoff at Mac. Com" <samsonoff at mac.com>
Sent: Saturday, July 14, 2007 18:18 UTC
Subject: Source of 70 cm Microphoncs Found

> 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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