Re: Ubitx microphony

Bill Cromwell <wrcromwell@...>
 

Hi Alf,

It is entirely possible for the vibration from the speaker to rattle the microphonic parts on the board. Remove the speaker from that equation by using an external speaker at some distance. That will remove the speaker vibration induced microphonics and expose any remaining distortion from an overloaded amplifier that is probably clipping. If the speaker is causing some distortion on strong signals as you have described that would be in addition to clipping.

Turn the volume down to reduce the clipping. Use the external speaker to reduce the microphonics:)

73,

Bill KU8H

On 12/25/18 9:23 PM, Alf Baranda via Groups.Io wrote:
Ok Peter, the same thing happens to me but in my Bitx40.
When I gently touch the pcb and the components near the AF ic with a stick, I hear the friction on the loudspeaker as a result of microphony.
This occurs even when the Bitx40 receives perfectly.
When the signals coming out through the loudspeaker are loud they distort and I am beginning to think that it is because of this microphonic effect, which is fed back by the sound of the loudspeaker.
I replaced the Lm386 without a positive result.
Keep investigating.
--
bark less - wag more

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