Radio Frequency Systems Inc 48810 Manual Do Utilizador
causes the composite power to exceed the safe level, the AGC's comparator generates a DC voltage
to a pin diode attenuator that increases attenuation in proportion to the level of the DC voltage.
to a pin diode attenuator that increases attenuation in proportion to the level of the DC voltage.
The attenuation reduces the output power until the detector voltage is at a safe level again. If the
number or power of the signals is reduced, the DC offset voltage will reduce the level of attenuation.
In typical operation, the AGC is only active when needed to prevent overdrive. If the AGC is
constantly activating, RFS suggests that you reduce the gain via the manual attenuator and verify
that an oscillation between the base and service antenna systems does not exist.
number or power of the signals is reduced, the DC offset voltage will reduce the level of attenuation.
In typical operation, the AGC is only active when needed to prevent overdrive. If the AGC is
constantly activating, RFS suggests that you reduce the gain via the manual attenuator and verify
that an oscillation between the base and service antenna systems does not exist.
AGC in the uplink is rarely needed in modern radio installations. As a portable comes closer to the
internal antenna network, its signal becomes stronger at the base site. Typically, the dynamic power
control at the base will turn the portable's power down to reduce interference and conserve power.
internal antenna network, its signal becomes stronger at the base site. Typically, the dynamic power
control at the base will turn the portable's power down to reduce interference and conserve power.
Overdrive is more likely to occur on the downlink path. All active signals at the donor base site will be
amplified by the repeater regardless of whether or not they are in use in the service area. Ideally, the
donor antenna is directional. This limits the number of donor base sites the repeater recognizes and
reduces the potential for interference. RFS recommends that you observe the signal levels before
connecting the repeater. While the extensive filtering in the 48810 will reject out-of-band signals by 80
dB, exceptionally strong out-of-band signals can cause overdrive. The most likely cause of an
overdrive condition is oscillation from inadequate antenna isolation.
amplified by the repeater regardless of whether or not they are in use in the service area. Ideally, the
donor antenna is directional. This limits the number of donor base sites the repeater recognizes and
reduces the potential for interference. RFS recommends that you observe the signal levels before
connecting the repeater. While the extensive filtering in the 48810 will reject out-of-band signals by 80
dB, exceptionally strong out-of-band signals can cause overdrive. The most likely cause of an
overdrive condition is oscillation from inadequate antenna isolation.
Table 1 lists the typical output power per signal, which can be expected from the 48810 for a given
number of active signals operating at equal input levels. For a donor site that has 3 signals, the full
power per signal would be +10 dBm, assuming the incoming signal is sufficient so that that level will
be achieved.
number of active signals operating at equal input levels. For a donor site that has 3 signals, the full
power per signal would be +10 dBm, assuming the incoming signal is sufficient so that that level will
be achieved.
Number of signals
dBm
1 15.0
2 12.0
3 10.0
6 7.0
2 12.0
3 10.0
6 7.0
12 4.0
T
ABLE
1: T
YPICAL OUTPUT POWER PER SIGNAL
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 87 dB, the
resulting output will be +7 dBm, not +10 as noted in the previous paragraph. +14 dBm in this case is
the maximum output allowed under any condition. So, if the incoming signal is -70 and the gain is set
for 87 dB, the output would not be +17 dBm with 3 simultaneous signals, the AGC would reduce the
gain to 80 dB and the output to +10 dBm per signal.
repeater. If a signal level of -80 dBm exists at the input to the repeater and the gain is 87 dB, the
resulting output will be +7 dBm, not +10 as noted in the previous paragraph. +14 dBm in this case is
the maximum output allowed under any condition. So, if the incoming signal is -70 and the gain is set
for 87 dB, the output would not be +17 dBm with 3 simultaneous signals, the AGC would reduce the
gain to 80 dB and the output to +10 dBm per signal.
AGC Automatic Shutdown
When the automatic gain control circuit reaches its limit (20 dB), the power amplifier stage is shut
down to prevent harmful distortion and potential damage to the repeater. 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.
down to prevent harmful distortion and potential damage to the repeater. 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,
bottom of the unit. These are pre-set in the fully counterclockwise position, at minimum attenuation,
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