Nearly constant sidetone level #qcx

Wolfgang DK4RW

The QCX sidetone level depends on the “Sidetone volume” parameter in the “Keyer” menu, but also on the setting of the gain control potentiometer R36. Therefore, when the gain control is turned up for a weak signal the sidetone level increases also, often to an uncomfortable level. For strong signals the gain needs to be reduced by turning down the gain control. This reduces also the sidetone level, which is then sometimes too low. For me changing the menu setting for the sidetone level while operating is too cumbersome and not an option.

There is a simple hardware solution. With a few components the gain potentiometer can be bypassed during transmit. The attached circuit does not completely eliminate the influence of the setting of R36 on the sidetone level. It just reduces the sidetone level change to approx. 6 dB for R36’s entire range (min to max). That is good enough for my needs.

73 Wolfgang DK4RW

PS: in my QCX the pin labeled “AGC” is connected to the drain of the BS170 in James’ audio AGC