Thanks Chris, Arv and Ashhar for comments and advice re the squeak.
I have checked and the relevant diode is in place. I removed the
decoupling electrolytic cap. from pin 6 of the LM386. Interestingly
it had no detectable effect on the function of the amplifier and the
squeak which occurs on changing from transmit to receive was the same
as before. It seems that there is some residual current in the
transmit phase of BITX which causes this pop.
John G0UCP
