AMERITRON ALS-606, Instruction Manual

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Version 0A 30
1KWF6 Low Pass Filter Assembly
The PAM-606 module connects directly to the 1KWF6 circuit board assembly through a
50-ohm cable. Power enters the filter system through a directional coupler consisting of
current transformer T2, capacitors C36-38, C40-42, and resistors R4, 5 and 6. This
directional coupler detects termination errors at the filter’s power amplifier side. These
errors include filter band errors. A comparator on the CB2 control board monitors
directional coupler termination errors. Any significant filter or antenna reflected power
error disables the amplifier. Such errors normally come from selecting the wrong filter
for the exciter’s operating band, or having a poor load SWR on the amplifier.
The filter board directional coupler output routes through one of seven 5-pole low pass
filter groups. Relays, controlled by CB2 control board logic, select appropriate low pass
filter components.
Control and Protection Logic
The CB2 control board contains all protection and control logic. In the event of an
operational fault, the CB2 locks out the amplifier and illuminates the proper front panel
warning light sequence. The CB2 also contains bias, relay sequencing, and fan speed
controls.
The CB2 board contains band-decoding systems, and automatically disables operation
between 25 and 28 MHz in all ALS-606 amplifiers. The embedded 25-28 MHz lockout
function cannot be disabled or changed.
SWR Directional Coupler
The rear panel directional coupler board samples line current and line voltage, vector
summing line voltage and current samples before conversion to a dc output voltage.
The resulting forward and reflected voltage represents forward and reflected power. The
ratio of forward to reflected samples represent mismatch from ideal 50-ohm loads.
Circuit Boards
There are ten basic circuit boards plus one power amplifier modules in the ALS-606.
The text below gives a brief description of each board’s function.
1KWF6
The 1KWF6 is a 1kW rated low-pass filter. It is the very large topmost board with
several large toroids and air wound inductors. This board contains filter input SWR fault
detection and seven low-pass 5-pole filters. Additionally, antenna relay board RLY
attaches directly to the 1KWF6 board.
BSW3
The BSW3 is located behind the BAND switch. It provides all band selection functions,
as well as band indicators.