User's Guide

1010
In all cases, the actual signal output power is equal to the input signal power plus the gain of the
repeater. If a signal level of -80 dBm exists at the input to the repeater and the gain is 65 dB, the
resulting output will be –15 dBm dBm, not +9 as noted in the previous paragraph. +9 dBm in this
case is the maximum output for 16 channels.
AGC Automatic Shutdown
When the automatic gain control circuit reaches its limit (25 dB typ), the power amplifier stage is shut
down to prevent harmful distortion and potential damage to the booster. 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 causing AGC to
reach its limit is removed. Conditions that can cause AGC to reach its limit 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
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 so these attenuators can be used to
reduce overdrive while maintaining AGC range. 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, .315 amp 250VAC
slow-blow fuse is used. A 2 amp, 32 VDC, fast-acting fuse is located on the side of each amplifier to
protect the DC voltage path. (See “Component Location”)
Ö Always unplug the amplifier before servicing the interior.
Ö Never insert conductive objects into any opening.
Ö Never remove or probe under the plastic safety shield covering the AC terminals of the 24
VDC power supply.
Ö 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 48900. 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.