This prevents the generation of harmonics.
Please share this information with your friends.
Also, on some stations, the audio input level may seem too high for the rig. Sometimes spurious signals are being transmitted at the same time.
The adjustment method is as follows. This method is the same for JTDX / WSJT-X / MSHV. Use the output adjustment sliders: the upper right slider for JTDX, and the lower right slider for WSJT-X and MSHV.
1. Set the rig output to 100%.
2. Set the output adjustment slider to maximum.
3. Show ALC on the rig's display.
4. Try transmitting at an appropriate frequency. You can call CQ or whatever like "VVV [your call]". Also it is OK to adjust during the actual communication.
5. Check the ALC meter display on the rig. In most cases the ALC should be swinging.
6. Lower the output adjustment slider little by little.
7. Check if the ALC swing width is getting smaller and smaller. In most cases the output itself will not drop.
8. Set the output adjustment slider just before the position where the output decreases.
9. Depending on the rig, the slider position may differ for each band.
10. From now on, the output should be adjusted by this slider, not the rig.
WSJT-X / JTDX can store the output for each band. If you adjust the output with the tune button, the slider position will not be reflected in the slider position during "FT8 operation".
Remember the position of the slider at the time of tune and adjust it at the time of operation, or adjust while outputting the FT8 signal without using tune. The display of minus several dB is displayed when the slider is moved.
The FT8 signal is single tone and is the same as the CW signal per unit time. Therefore, there is no problem even if you swing ALC.(Of course, an excessive audio input level that causes the ALC meter to go far beyond the proper range tends to distort the signal, even for a single tone.) However, if the audio signal itself from the PC is distorted, it will not be single tone and the radio waves will be distorted. The best way to prevent this is to avoid shaking the ALC.
This is a "precautionary measure" because it can prevent excessive audio input to the rig.