Wideband digital signal processing (DSP) is applied directly after data is read from the radio and before any waterfall, spectrum or demodulation.
The auto mute feature automatically blanks the waterfall and mutes the audio when a strong signal is detected. This is a very useful option to have in a SDR console, apart from anything else it ensures no audio feedback if you are listening on or close to your transmission frequency. Auto-mute is a simple approach to handling strong signal overload situations.
Note: normally you use the External Radio support when transmitting with an external 'standard' transceiver (eg FTDX-5000) and receiving with a SDR receiver (eg NetSDR). This logic can be used in conjunction with the External Radio support as the software will usually not immediately detect when the external radio starts transmitting.
The Auto-Mute logic runs directly after data is read from the SDR receiver and before the waterfall (FFT) processing, so the data is still in the time domain (FFT processing converts to the frequency domain). The Current values will not correspond directly with the values in the waterfall.
The interface is accessed from the ribbon bar: Home, Wideband DSP.
Click Options to display the configuration window:
To enable auto-mute the data from the radio must be greater than the peak and/or mean threshold. So far experience has shown that the mean threshold is the best value to use.
Suggested settings when using an external radio in VOX are:
The Current values can be used as a guide, the value you select should be greater than the current when a strong signal is not present.
If using this option in conjunction with External Radio support the mute and restore levels can be reduced, use trial-and-error.
The wideband noise blanker is based on a design by Warren Pratt (NR0V), implemented in his WDSP library (more below). A noise blanker removes very short noise pulses of high peak energy (pops, crackles), these are seen as horizontal lines in the waterfall and heard in the audio. Reduce the Threshold level until the noise peaks are removed - if the threshold is too low audio will be distorted and there will be 'smearing' in the waterfall. Typically the Blanking level will be less than 1% (the percentage of all samples which are modified by the noise blanker).