Instruction Manual

6X Series Liquid-Cooled Transmitter Chapter 2, System Description
Instruction Manual, Rev. 0 2-4
2.3: Power Amplifiers
The Axcera 6X Series transmitter is comprised of highly reliable broadband amplifier
modules operating in a parallel configuration. Each module uses the latest LDMOS
transistors, providing very efficient and linear operation and the highest power
density available today. For convenience, each amplifier module operates
independently, allowing easy removal and replacement while the transmitter is on
the air. All power amplifier modules are interchangeable. The extensive correction
capability of Axcera's digital exciter allows all stages of the final amplifiers to operate
in the very efficient class AB mode, minimizing system power consumption.
The broadband amplifier design allows all modules to operate over the entire
operating band without any retuning, helping to minimize spare parts stock for
multiple station operators. This also provides for simplified channel changes,
requiring only replacement of channelized filters.
The fan power supply board and the amplifier pallets operate using +42 VDC from
the buss bar assembly through 30 Amp fuses. Two spare 30 Amp fuses are mounted
on the Fan Power Supply Board.
2.4: Combiners
Each Axcera 6X transmitter employs progressive combiners, to combine the power
amplifier modules. This design is very low loss, for optimal overall system efficiency,
and utilizes liquid-cooled reject loads to minimize size. The progressive combiner
design is very modular, allowing for systems to be configured for lower power levels
and easily upgraded with additional sections for future migration to higher power.
The combiner system is mounted in the rear of the amplifier cabinet, immediately
behind the amplifier modules and adjacent to the cooling plenum, minimizing
required cabling.
2.5: Liquid Cooling System
The liquid cooling system is made up of three primary systems:
1) PA Cabinet Distribution – Cooling liquid is distributed equally to all power
amplifiers and power supplies within the power amplifier cabinet through a water
manifold located in the rear of the cabinet. Each amplifier module and power
supply plugs directly into the manifold through two drip-less blind-mate
connectors, one input and one output. This minimizes the plumbing required
within each power amplifier cabinet.
2) Control and Pump Rack – This rack houses the cooling system controller, dual
pump system (n+1 configuration optional), cooling liquid reservoir, bleeder
valves, and debris filters. The control system monitors temperature in various
places throughout the transmitter system and maintains consistent
temperatures, independent of ambient temperature changes, in order to reduce