MX940 Base Station & Repeater
Technical Manual
© SPECTRA ENGINEERING
2022 Revision 1.0.0
14
The channel may be edited via the Channel Edit Screen of the built menu system
software. The current operational channel can be selected by using the software
channel select command.
The MX940 comes from the factory pre-aligned, so in most cases adjustment will not
be required. The MX940 employs Frequency Alignment Compensation, which is
setup during factory alignment.. This reduce the need of individual channel alignment
for Tx Power and modulation depth. If however adjustment are required on a
particular channel this can be done via the built in alignment menu. See section 4.1.8
for TX power adjustments and section 4.1.9 for modulation alignments.
4.1.4 Setting CTCSS/DCS
MX940 Controller CTCSS Setup:
1. The RF channels that are required to be CTCSS controlled should be programmed
with the required CTCSS Subtone in the TX and / or RX channel fields.
MX940 CTCSS / DCS Testing:
1. The use of the DCS / CTCSS encoder / decoder will require a ‘Peak Deviation
and Modulation Balance Alignment’ as per Section 4.1.9 of the Technical manual.
This alignment is to be performed without the CTCSS frequencies or DCS codes
programmed into the alignment channel as the subtone levels will give a false
indication of the peak deviation levels. The MX940 contains circuitry that
automatically scales the deviation so the nominal deviation is not exceeded when
a sub tone is transmitted.
4.1.5 Power Calibration
DO NOT USE THIS PROCEDURE TO SET THE TX OUTPUT POWER.
REFER 4.1.8 TX POWER ADJUSTMENT TO DO THIS.
Power calibration affects the forward and reflected power meters on the Diagnostics
Screen. This procedure requires a power meter and the relevant leads to connect the
transmitter output to the meter. Power calibration is done using software commands.
To complete the power calibration send the command CALP <enter>, and follow the
instructions that Built in menu system provides.
These readings are subsequently used for the real-time update and display of the
VSWR. The live VSWR values are used in the PA protection routines in the firmware.
4.1.6 RSSI Calibration
The RSSI calibration is used to calibrate the RSSI meter on the in-built menu system
via Diagnostics Screen. The procedure requires an RF signal generator and the
relevant leads to connect the signal generator to the RF input of the MX940 Base
Station. RSSI calibration is done via software command To complete the RSSI
calibration send the command CALR <enter>, and follow the instructions that in-built
menu system provides.