Jim, I guess we have a small progress ! I have removed C21 and the loud tone is disappear...but nor completely...
Now If I put the volume to zero I am now able to listen the "white noise" typical of a radio without antenna, and when I increase the volume this is the matter: considering volume from o to 10, volume 0 = just white noise, volume 3 appear the tone but stll possible to hear the white noise in the background, volume 6 the tone is stronger, and still a white noise very weak, volume 9 just the tone.
I have noted that if I power on the QCX wearing the earphone, until the display show "5W CW TCVR 1.09 QRP Labs 2021" the tone is not present, as soon the dispaly show the frequency, the tone appear... is this a fact that help to understand further ?
Best 73 de IK1TTD Gianpi.?
