Technical Manual
Installation and Operation
© SPECTRA ENGINEERING 2022 Revision 1.0.0
17
4.1.11 Nominal Deviation
The required nominal deviation is dependent on whether the radio is programmed for
either narrow or wide. The following table lists the required level for each case:
Bandwidth
FM Nominal
Deviation (kHz)
Narrow (12.5kHz spacing)
1.5
Wide (25kHz spacing)
3.0
Table 4-2 Nominal Deviation
.
4.1.12 Mute Threshold Setting
Test Equipment:
PC with Terminal software
RF Communications test set
+13.8VDC power supply
MX940 Testing – Rx Mute:
1.
Monitor the front panel RX Led with the base station connected to a RF
Communications test set. Inject the correct RF frequency into the receiver for the
test channel. Set the test set generator to the desired muted amplitude (i.e -
119dBm) , then set the squelch level (i.e. 2) via programmer or Using in-built
menu system channel edit screen. Test your setting by reducing the RF generator
amplitude until RX Led is off .
2.
Re-adjust the squelch level (Mute control) so that the RX just goes into the muted
condition RX Led off, for the desired RF amplitude.
Ideally, the squelch level should be set just above the background radio noise
level or at the point where the typical desired signal is becoming too noisy to be
acceptable. A higher setting of squelch level requires higher received signal
strength to un-mute the receiver. A “0” level indicates that there is no squelch
suppression function, which is the lowest level.
Further information on setting mute (squelch) can be found in Section 1.1.1
