User's Manual

RHBDA OPERATION
Refer to figure 3 for adjustment access location and label.
Variable Step Attenuator
The RHBDA’s gain can be reduced on the Rack Unit by up to 30 dB on the Uplink
and Downlink, in 2 dB steps using the variable step attenuators. Gain adjustment is
made with rotary switches accessible via the Front panel on the RHBDA enclosure.
Arrows on the shafts of these switches point to the value of attenuation selected.
RHBDA gain can be determined by subtracting the attenuation value from the gain
reported on the RHBDA 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, each amplifier in the RHBDA contains an ALC
feedback loop. The ALC circuit senses the output power and limits it to the factory
preset level of +5 dBm for the Uplink and +36 dBm for the Downlink. Two red
indicator lamps are located on the Front panel which illuminate when the output
power exceeds the ALC set point.
Two red indicator lamps are located on the Front panel which illuminate when the
output power exceeds the ALC set point.
To establish proper operating gain on the Rack Unit, start with the Downlink. Observe
the red indicator lamp on the front panel. 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. The
Uplink ALC function is to avoid overloading the fiber optic transceiver. Setting the
attenuation of the Uplink will depend on minimum and maximum distance from the
mobile to sever antennas. The level indicator is accurate to +/- 0.4 dB of the ALC set
point.
Operation of the RHBDA-PS8-0.1/25W-55-A at maximum gain (Minimum
Attenuation) with greater than -10 dBm average power incident on the MOBILE
port may cause damage to the RHBDA.
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