Remodel the air band RX kit for silent squelch switching

Arduino and Si5351a bring me a stable radio to watch the communication dispatch but I was annoyed squelch switching noise.

I investigated the circuit how to work by LTSPICE. Simple diode switching causes LM386 abnormal oscillation of several Hertz. Noise level is full swing of LM386 operational point. Please look at the simulation waveform. Squelch is opening, closing, and opening again. There is several Hertz noise on closing and at the start point of opening.

I remembered that Mr.Chiba recommended to switch LM386 by weak biasing on the input nodes.

I added some resisters for that and got good result.

After remodeling the circuit, there is not such noize on switching.

Please confirm by YOUTUBE video.

https://youtu.be/78jJ35Vm3pY

Please visit my BLOG.

https://nobcha23.hatenadiary.com/entry/2022/01/01/224343