User's Manual

N.O.
COM.
N.C.
BDA OPERATION
Refer to figure 4 & 5 for adjustment access location and label.
Variable Step Attenuator
BDA gain can be reduced by up to 30 dB in 2 dB steps using the variable step
attenuator (Figure 5). 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.
Alarm Function
The alarm monitors current of both uplink and downlink amplifiers in each path. An
alarm condition will occur in each path if either the uplink or downlink amplifiers are over
or under its current tolerance or there is no supply power present.
(Relay Shown in Non-Alarm Condition)
Re-banding Switch
The re-banding switch changes the frequency of operation in the ESMR 800 band from
uplink (806-824 MHz) and downlink (851-869 MHz) to uplink (817-824 MHz) and
downlink (862-869 MHz). There is no tuning require, just select the narrow SMR
position when re-banding occurs. (See Figure 5)
ALC (Automatic Level Control)
To minimize intermodulation products, each amplifier in the BDA contains an ALC
feedback loop. The ALC circuit senses the output power and limits both Uplink and
Downlink to the factory preset level of +26 dBm. A red indicator lamp located on the
control panel illuminates when output power 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 Downlink amplifiers. Units are shipping
with maximum attenuation. Decrease attenuation one step at a time until the lamp is lit.
Then, using the each 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.
Operation of BDA-ESMR-2/2W-80-AN89R at minimum attenuation with greater
than -40 dBm average power incident on either BASE or MOBILE port can cause
damage to the BDA.
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