User's Manual

G3S-800-140 Installation & Service Manual
044-05095 Rev. A 4-3 February 2001
4-4.4 Amplifier Module Cooling
Although each amplifier module contains its own heat sink, it is cooled with forced air. Four fans
are used for forced air cooling and redundancy. The fans, located on the front and rear of the
amplifier module, draw air in through the front of the amplifier and exhaust hot air out the back of
the module. The fans are field replaceable.
4-5 Power Distribution
Primary DC power for the system is provided by the host system to the MCR30830-1-3 Series
subrack. The subrack supplies each amplifier module with +27 Vdc directly and via the RF power
splitter/combiner. The amplifier module has a DC/DC converter that converts the +27 Vdc to +15
Vdc, +5 Vdc and -5 Vdc.
4-6 Intermodulation
The G3S-800-140 amplifier is designed to deliver a 140-watt composite average power, multicar-
rier signal, occupying a bandwidth less than or equal to 25 MHz, in the bandwidth from 869 to 894
MHz. The maximum average power for linear operation, and thus the amplifier efficiency, will de-
pend on the type of signal amplified.
4-6.1 Two Tone Intermodulation
When measured with two equal CW tones spaced anywhere from 30 kHz to 20 MHz apart, and at
any power level up to the average power, the third order intermodulation products will be below
-60 dBc
4-6.2 Multitone Intermodulation
Adding more tones to the signal will lower individual intermodulation products. If the frequencies
are not equally spaced, the level of intermodulation products gets very low. When the frequencies
are equally spaced, those products fall on top of each other on the same frequency grid. The av-
erage power of all intermodulation beats falling on the same frequency is called the composite in-
termodulation; it is -60 dBc or better.
4-7 Alarms
The presence of several plug-in amplifier alarms can be detected at the DC and logic connector
on the amplifier rear panel. Refer to table 2-1 and figure 2-2 for a description of the connector.