[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 
C53.

73,

John
KD6OZH

----- 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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