User Manual

MCA9129-90-A Installation & Service Manual

044-05060 Rev. C 4-6 July 2001November 2002

4-5.3 Amplifier Monitoring

In the main and error amplifier modules, all normal variations are automatically compensated for

by the feedforward loop control. However, when large variations occur beyond the adjustment

range of the loop control, a loop fault will occur. The alarms are displayed in the front panel indi-

cators and output via a 21-pin connector on the rear of the module to the subrack summary board

for subsequent remote monitoring.

4-5.4 Amplifier Module Cooling

Although each amplifier module contains its own heat sink, It is cooled with forced air. Three fans

for are used for forced air cooling and redundancy. The fans are located on the front and rear of

the amplifier module, draw air in through the rear of the amplifier, and exhaust hot air out the front

of the module. The lower front fan is not monitored for failure as are the other two.

The fans are

field replaceable (refer to paragraph 5-6.2).

4-6 Power Distribution

Primary DC power for the system is provided by the host system to the subrack. The subrack

supplies each amplifier module with +27 Vdc directly and via the RF power splitter/combiner. The

amplifier module has linear and switching regulators that generates required DC voltages such as

a DC/DC converter that converts the +27 Vdc to +15 Vdc, +5 Vdc, +9V and -5 Vdc from +27Vdc.

4-7 Intermodulation

The MCA9129-90MCA9129-90-A amplifier is designed to deliver a 120-watt composite average

analog power, multicarrier signal, occupying a bandwidth less than or equal to 25 MHz, in the

bandwidth from 869-894 MHz. The maximum average power for linear operation, and thus the

amplifier efficiency, will depend on the type of signal amplified.

4-7.1 Two-Tone Intermodulation

When measured with two equal CW tones spaced anywhere from 30 kHz to 25 MHz apart, and at

any power level up to the peak power, the third order intermodulation products will be below

-65 dBc at 100 watts output, below –60 dBc at 120 watts output.

4-7.2 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 -65 dBc @ 100 W output, -60 dBc @ 120 W output, or better, with a maximum

of one MHz channel spacing.