Noise reduction
Noise reduction will reduce the background noise. There will be an optimum setting depending on the type of noise that you are encountering. For example, there may be different requirements for SSB, AM or FM.
Noise reduction can be turned on or off by selecting "Noise reduction > Noise reduction" in the menu.
Settings
The noise reduction level can be adjusted with the "Noise reduction > Reduction lvl" item in the menu. Larger values will reduce the noise more, but values that are too large will distort the signal and make it harder to understand (since some of the signal will be classified as noise and removed). A value of around 50 is often a good starting point. Values much above 80 are likely to distort speech too much, but may be useful for CW.
"Tone reduction": if this is turned on, then tones that are constant for more than a couple of seconds will also be reduced. This should be used if there are interfering constant tones in the input that cannot be removed by adjusting the bandpass filter. Otherwise, the output is often clearer with this turned off.
Discontinuous tones such as Morse code will not be removed by the tone reduction feature.
Advanced settings
"Noise percentile": this setting is related to how the WOLFWAVE estimates the noise level in the input signal. If this is incorrect, then possible effects include:
- noise reduction may be much stronger or weaker than it should be for a given "Reduction level" setting
- noise reduction may not adapt correctly to changes in input level caused by the radio's AGC
- if it is too high, signals may be distorted or suppressed
The correct noise percentile to use depends on the passband of the input to the WOLFWAVE (i.e. the passband of the radio that is connected to the input, not the passband of the WOLFWAVE's bandpass filter).
It can be estimated with: noise percentile = 100 - bandwidth x 90 / 5000
For example, a radio output bandwidth of 700Hz means the noise percentile should be set to around 87%.
The default value is 50%, which should be about right for a radio passband suitable for SSB signals.
"Time constant": the estimate of the noise level in the input signal is averaged over time. This setting controls the time constant for the averaging and hence how fast it adapts to changes in noise level. The time constant should be short enough to keep up with the radio's AGC. If it is too large, then the noise reduction will be worse (noise not reduced enough, or signal reduced as well as noise) for a short time after each AGC gain change, such as when someone starts or stops speaking.