[Hallicrafters] Piesoelectric effect case in point.

[Roger (K8RI)]

On 1/2/2011 4:31 PM, Glen Zook wrote:
> There may not be any way that a ceramic disc capacitor can become a transducer,
Almost anything can become a transducer.  A transducer is just a device 
for generating a signal. Two wires, the plates of a capacitor, a 
thermistor, etc.  It doesn't have to actually use the piezo effect. Most 
transducers don't.
>   but I have, on very rare occasions, heard audio coming from a disc ceramic capacitor that has been used for coupling in an audio circuit.  Replacing the capacitor, usually with a "poly" type, has cured this "problem".
>
Some caps can certainly become "microphonic" if one or both plates 
separate from the dielectric.

73

Roger (K8RI)
> I have also run into an occasional problem where, when "tapped", a disc ceramic capacitor did act microphonic and introduced the "sound" into the audio chain.  Have run into this on both transmitters and receivers.
>
> Probably, replacing with another ceramic disc might have solved the problem.  One that did not have whatever "defect" which caused it to act like a speaker.  However, when I do experience this I just replace the disc ceramic capacitor with a different type and go on to the next problem.
>
> Glen, K9STH
>
> Website:  http://k9sth.com
>
>
> --- On Sun, 1/2/11, rbethman<rbethman at comcast.net>  wrote:
>
> Having just researched ceramic capacitor construction, I don't see ANY way that these would have the ability to become a piezo transducer, OR having anything to do with these old boatanchors.
>
> You "may" want to do a bit of research also.  They also manufacture "dipped ceramic" capacitors.
>
>
>
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