...
 

Introduction

Added October 22nd, 2016 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.

  • An alternative to External Radio support,
  • Simple to configure,
  • No cables needed!

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.

  • Data buffer read from radio, usually in intervals of 5 milliseconds
  • Current peak and/or mean level for the buffer compared to the maximum possible level (usually use the mean level)
  • If the peak and/or mean exceeds the configurable threshold the mute / restore logic is applied
  • During the mute phase the radio data is set to zero, no audio is heard, the waterfall level is zero
  • During the restore phase the signal level restored to the normal level (similar to an AGC)

 

 

Configuration

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:

  • Peak: disabled
  • Mean: enabled, -30dB to -50dB threshold
  • Mute: 100ms
  • Restore: 50ms

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.