User Manual

ITEM # 602100022500
DOCUMENT TYPE: Operation and Installation Manual
REV: 0
DOC #: 602100022500
PAGE 10 OF 17
TITLE: Bi-Directional Amplifier System
AGC Automatic Shutdown
If the attenuation capability of the AGC circuitry is exceeded, power to the power amplifier stage is
shut down to prevent harmful distortion and potential damage to the 48760. Shutdown will occur if the
AGC control limit is exceeded for about 1/2 second. Power is then cut for two seconds. After this
timeout, power is brought back on-line. If the overload condition is still present, shutdown will again
occur in approximately one second. This cycle will be repeated until the condition is removed.
Conditions that can cause AGC to shut down include the presence of one or more very strong
channels, a strong in-band noise source, or amplifier oscillation due to inadequate antenna isolation.
Manual Gain Adjustment
The independent manual attenuators, RX for uplink and TX for downlink, are accessible from the
faceplate on the bottom of the unit. These are pre-set in the fully counterclockwise position, at
minimum attenuation, maximum gain. Manual attenuation is separate from the AGC attenuators. At
the full clockwise position, >20 dB of attenuation will be introduced in the respective gain path.
AC/DC Power
AC power is supplied through a standard 3-wire male plug connected through a standard IEC-320
plug. Connect this plug to any standard 3-wire 120-240 VAC outlet. A 5x20 mm, medium time lag
fuse 3A/250v. A 5 amp mini ATO fuse is used between the 28 VDC from the power supply and the
control board, which distributes the power to all components. This fuse is located on the control
board.
⌦ Always unplug the amplifier before servicing the interior.
⌦ Never insert conductive objects into any opening.
⌦ Never remove or probe under the plastic safety shield covering the AC terminals of the 24
VDC power supply.
⌦ Always use a standard 3-wire electrical outlet, with safety ground, for connection to AC
power.
Grounding and Surge Protection
The unit is case grounded through the three-prong plug. The donor antenna feeder cable should
have a cable ground attached to it, along with an inline surge arrestor between the donor antenna
and the 48760. The distribution network need not be grounded in building installations. However, the
distribution network in tunnels, subways or outdoor installations should also include a cable ground
and inline surge arrestor at or near the “service” port.
DANGER
Always remove power before checking or changing fuses. 120VAC can be lethal.