The Siglevel detector analyzes the noise component in the AF signal and uses it to develop a criterion for the squelch. For this the squelch of the radio must be constantly open, i.e. without carrier a squelch must be heard, with carrier of course none.
To use the SigLevel-Detector you have to calibrate it first.
The best way to do this is as follows:
1) First configure a VOX as squelch criterion (SQL_DET=VOX), close the squelch of your radio just so that the noise disappears.
2) Guide QSO’s and use the alsamixer to optimally adjust the NF level on the transmitter and receiver sides.
3) Now change SQL_DET=VOX to SQL_DET=SIGLEV.
4) Open the squelch of your radio
5) start the supplied program sigleveldetcal, which calibrates your squelch, the call of the program is:
siglevdetcal config-file receiver-section
siglevdetcal /etc/svxlink/svxlink.conf Rx1