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Technical Manual
When setting up the radio it is recommended that all measurement and adjustments
are done on a channel that is in the centre of the frequency spread of the channels.
This minimises any errors due to frequency changing. Alternatively if the frequency
spread of the channels is too large then you may wish to calibrate and align every
channel. (In most cases this will not be necessary). Both individual and group
alignment will be covered.
The channel may be selected via the Channel Screen in built menu system software,
using the software channel select or in hardware via the front channel select.
7.1.4 Setting CTCSS/DCS
SMX920 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.
SMX920 CTCSS / DCS Testing:
1. The use of the DCS / CTCSS encoder / decoder will require a 'Peak Deviation
and Modulation Balance Alignment' as per Section 7.1.9 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 SMX920 contains circuitry that
automatically scales the deviation so the nominal deviation is not exceeded when
a sub tone is transmitted.
7.1.5 Power Calibration
DO NOT USE THIS PROCEDURE TO SET THE TX OUTPUT POWER.
REFER 7.1.8 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 in built menu system
via the Calibration Screen. To complete the power calibration, 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.
7.1.6 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 SMX920 Base
Station. RSSI calibration is done via Calibration Screen. To complete the RSSI
calibration, follow the instructions that in built menu system provides.
7.1.7 Temperature Calibration
The temperature calibration is used to calibrate the temperature meter on the in built
menu system via Diagnostics Screen and the temperature controlled switch/alarm
points. The procedure requires dummy cable for SKB on the micro controller having a
RELM/
BK RADIO
Installation and Operation
27
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