For a while I used a headset with microphone with my SunSDR DX. Every time I made a QSO in the background the participants made me aware that my audio signal was accompanied by an unbearable echo! At first I checked all the microphone settings, equalizer etc. but I could not eliminate the echo effect. I was dissatisfied and began to doubt my radio. Then I had a flash and decided to change the microphone. A microphone separate from the headset and to my surprise the echo effect no longer existed. However, I could not understand why the headset / microphone combination created echo problems for me. This is my experience! good dx to all of you. below you can find my QSL card on which my station is described. 73 de Arturo, HB9MIR