Re: ubitx receive audio troubleshooting

Gordon Gibby
 

So in order to have an oscillation, you have to have a closed loop with a gain greater than one at the oscillation frequency

Since your squeal begins when you turn the vine control up, and then input of the loop that Apparently exists is earlier in the system.  

My guess would be via the power supply lines.  That would suggest adding additional filtering in Decoupling capacitance in parallel with the lowest inductance (short leads ) as possible as near to the chips involved as possible.   Probably the audio Amp chip & its preamp should have additional filtering on the power supply lines.  You can test this by  merely touching capacitance to the proper places temporarily.


On Feb 4, 2018, at 13:21, radiodoc43 <Monsen.Craig@...> wrote:

My mistake. I meant TDA2822 chip.

Craig
KC2LFI

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