Detect settings menu - Gain
This parameter is responsible for amplifying the signal of the device.
The higher this parameter is, the deeper and smaller targets can be detected.
The lower it is, the lower is detecting depth. But the device becomes more resistant to ground mineralization and ground conductibility.
So this parameter is a compromise and must be set for a specific location.
Before you begin lowering sensitivity using ST or RT, you should first try to lower it with gain parameter. Without even touching ST or RT till the moment the gain setting is at minimum.
So, if you get phantom signals or some other kind of interference, it will be a good idea to set gain a little lower. This will let you work in silence and to find at least the targets available in current situation.
Keep this setting at the level that is comfortable for you. Because comfortable search will bring better results, than searching while being unable to hear anything because of constant phantom signals or electromagnetic interference.