User 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 +25 dBm on the Uplink and +35 dBm on the Downlink.
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 the ALC’s turned ON.
To establish proper operating gain on the Uplink and Downlink sides, start with the
Uplink. Verify that the ALC switch is in the “ON” position. Observe the red indicator
lamp on the Uplink amplifier. 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 Downlink. 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-SMR-1/25W-90-O at maximum gain with greater than
-45 dBm average power incident on the MOBILE port or greater than -35 dBm
average power incident on the BASE port can cause damage to the BDA.
Page 12