In the Sensitivity Zoom window, you see the signal strength at a percentage of when the detector overloads. This isn't on any specific frequency - the reading is on the incoming signal before it has been separated into the 3 frequencies. The goal is to keep the ground signal about 10% so that you still get depth and can still see shallow targets without overload. Signal% doesn't indicate signal "loss", but rather the amount of residual signal present. If ground + null are the cause, then this doesn't take away from sensitivity. Instead, it takes away from large/shallow target response, manifested in signal overload. None of these are losses, but rather they reduce the available dynamic range. The lower this % number the stronger the signal will come through or be received.
The Noise% measures the External Interference. 0% or a low number indicates very little external noise and low ground interference, thus allowing for using a higher preamp RX Gain. A high % reading of Noise of 50% or more would require you to:
Reduce the RX Gain
Use a different frequency on your program
Use a smaller search coil.
High Signal to Low Noise Ratio. Cranking up the Gain or Sensitivity obliterates a good signal with an increase in noise. Particularly small and deep targets get the worse treatment. EMI shows up as chatter and reduces the low end, minimum detectable signals. Ground causes overload or makes GB difficult and the reduction is on the high end, large/shallow target overload. If you are hunting in a clean area with only deep targets, then run the gain just below the overload point for max depth. But if there are a lot of shallow targets, then this will result in a lot of audio overload signals which might be annoying.
Rob
