Futurecom Systems Group ULC. CMDUHF Manuale Utente
8M074X01-01 Rev.1
11
7.4 BASICS OF GAIN SETTING
The following Steps set the output power and gains in the Channel Module. (Note that setup must be
performed for both the Downlink and the Uplink.)
performed for both the Downlink and the Uplink.)
The basic rule for setting the gain can be summarized as follows:
For OCR Mode (Receiver Frequency equals Transmit Frequency):
The total gain of the Channel Module must always be less than isolation between receive and
transmit antennas and cables. A 10dB minimum margin is recommended.
The total gain of the Channel Module must always be less than isolation between receive and
transmit antennas and cables. A 10dB minimum margin is recommended.
For non-OCR Mode (Receiver Frequency is different from Transmit frequency):
The total gain of the Channel Module must always be less than
The total gain of the Channel Module must always be less than
ANTENNA ISOLATION + SPURIOUS LEVEL - 10dB
where
where
ANTENNA ISOLATION = isolation between receive and transmit antennas and
cables.
SPURIOUS LEVEL = the difference between transmit output power and
spurious of Tx signal on Rx frequency. This difference is typically 75dB.
cables.
SPURIOUS LEVEL = the difference between transmit output power and
spurious of Tx signal on Rx frequency. This difference is typically 75dB.
Frequency
Tx Power
Tx
Rx
SPUR LEVEL (75 dB Typ.)
The normal setting is such that the gain is lower than the isolation by a 10 dB margin. A larger margin
accounts for environmental, ageing and other changes in the system.
accounts for environmental, ageing and other changes in the system.
If this basic rule is not followed, the Channel Module may become permanently locked in keyed-up
mode after first activation of the CMDUHF transmitter.
mode after first activation of the CMDUHF transmitter.
7.5 DOWNLINK GAIN SETTING
Downlink is the direction from the Channel module to a radio unit. The downlink settings are optimized
for a maximum transmit power from the Channel Module. Note that the antennas must be connected
for this procedure.
for a maximum transmit power from the Channel Module. Note that the antennas must be connected
for this procedure.
1. Select “Module Setup” field and then select “Setup” using cursor keys. Press <Enter>.
Wait for all the fields to be updated. Movement around the screen is done using cursor keys.
Modification of values in different fields is done with <Page Up>, >Page Down> or numeric
keypad <->, <+> keys. All fields starting with ”?” show measured values.
Modification of values in different fields is done with <Page Up>, >Page Down> or numeric
keypad <->, <+> keys. All fields starting with ”?” show measured values.