BDA OPERATION
Variable Step Attenuator
BDA gain can be reduced by up to 30 dB in 2 dB steps using the variable step
attenuator (Figure 3). Gain adjustment is made with rotary switches accessible
via the access door on the BDA enclosure. Arrows on the shafts of these
switches point to the value of attenuation selected. BDA gain can be determined
by subtracting the attenuation value from the gain reported on the BDA Test Data
Sheet for that side of the unit. The attenuators are labeled for Uplink and
Downlink.
ALC (Automatic Level Control)
To minimize intermodulation products, the Uplink amplifier in the BDA contains
an ALC feedback loop (Figure 4). The ALC circuit senses the output power and
limits it to the factory preset level of +
26
dBm.
ALC function is selected with on/off toggle switches located on each amplifier
and accessible when opening the door on the BDA enclosure. A red indicator
lamp located on each amplifier illuminates when output power meets or exceeds
the ALC set point. The indicator is functional regardless of the position of the
ALC switch.
Units are shipped with both ALC switches in the “ON” position. To ensure
distortion-free operation limited to the set point, keep both the ALC switches
turned ON.
To establish proper operating gain on the Uplink and Downlink sides, start with
the Downlink. Verify that the ALC switch is in the “ON” position. Observe the red
indicator lamp on the Downlink amplifier. Units are shipping with maximum
attenuation. Decrease attenuation one step at a time until the lamp is lit. Then,
using the Downlink step attenuator, increase the attenuation until the lamp goes
off. Repeat the process for the Uplink. The level indicator is accurate to +/- 0.4
dB of the ALC set point.
Note
:
The recommended operation of the BDA is
when the factory set ALC is turned on. Operation of the BDA in the alarm
condition will void the warranty, and output power should be immediately
reduced using the variable step attenuator.
Operation of BDA-CELLB-2/2W-80-OCA at maximum gain with greater than
-43 dBm average power incident on the MOBILE or BASE ports can cause
damage to the BDA.
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