User's Manual

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 +27 dBm on the Uplink and +37 dBm on the Downlink.
ALC function is located within each power amplifier. A red indicator lamp located on each
amplifier illuminates when output power meets or exceeds the ALC set point.
To establish proper operating gain on the Uplink and Downlink sides, start with the
Downlink. Observe the red indicator lamp on the Control Panel. Units are shipping with
maximum attenuation. Decrease attenuation one step at a time until the lamp is lit. Then,
using the Uplink 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: Long term operation of the BDA in an alarm condition will void the warranty, and
output power should be immediately reduced using the variable step attenuator.
Operation of BDA-CELLAB-2/25W-90-OA at maximum gain with greater than -55
dBm average power incident on the MOBILE port or greater than -45 dBm average
power incident on the BASE port can cause damage to the BDA.
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