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RF-8000E Operations Manual
Chapter 1. Overview — 3
Amplifiers
8. In digital radio applications, in order to maintain linearity over the entire signaling envelope, the
amplifiers operate at a reduced average power level to meet the output power level requirement
as shown in Technical Summary. Each amplifier is mounted on the front of the panel to allow
easy AGC/ALC and linear gain adjustments. It also provides easy amplifier replacement in the
field. Necessary information for ordering spare or replacement amplifiers is provided later in
Chapter 1,
Ordering Information
.
Directional Couplers
9. Directional couplers, built into the amplifiers, provide signal monitor points, “RF MON”. These
allow in-service measurement of transmit output power. The monitor points are calibrated for
calculating the actual RF output power at the amplifier output and at the antenna port flange.
When measuring transmit power, the power meter reading obtained, plus the loss (in dB) marked
at the amplifier monitor point, minus the branching loss (in dB) marked on the panel, equals
actual antenna port transmit output power.
Example 1 Amplifier Output
Example 2 Antenna Port Output
Power Meter indication
+5.0 dBm
Power Meter indication
+5.0 dBm
Cal Loss at RF MON
+ 19.0 dB
Cal Loss at RF MON
+ 19.0 dB
Amplifier Output =
+24.0 dBm
Tx Branch Loss
- 2.0 dB
Antenna Port Output =
+22.0 dBm
AGC/ALC Adjustment
10. There is a field-adjustable potentiometer on each amplifier. The amplifier output power set level is
adjusted by AGC/ALC potentiometer. This is a multi-turn potentiometer.
Linear Gain Adjustment
11. On each amplifier, there is a second field-adjustable potentiometer for linear gain adjustment to
limit its maximum gain. Gain adjustment is typically only used in cases where antenna isolation is
inadequate to support the required C/E at maximum gain. In the majority of cases, the AGC/ALC
automatic adjustments are all that is needed.
Power Supply
12. The only active element in each frequency channel of the RF-8000E assembly is the amplifier
which operates from a +11~16.5 VDC source. Current requirements are 1.95 Amperes maximum
for higher power Level 2 amplifiers. Solar Rated power consumption accounts for lower current
demands under normal conditions. The repeater assembly may be powered from alternative
energy source such as solar panels, wind turbines, thermal electric generators, fuel cell electric
generators, primary cells only, or from an AC/DC supply with standby battery (shown in Figures
18 and 19).
13. Optionally, the repeater can be configured for +24 VDC with the addition of internal DC-DC
converters. Two DC supplies of +24 VDC are brought into the repeater enclosure. They are
converted to +11.5 VDC by two DC-DC converters and power the amplifiers in redundant-
protecting mode. Current requirements, at +24 VDC, are 1.35 Amperes maximum per higher
power Level 2 amplifier.