SWR
The SWR board is a standard 50-ohm directional coupler. The SWR board samples output connector current
and voltage, vector summing voltage and current samples to a dc output voltage. The resultant voltages
represent forward and reflected power, or SWR mismatch, to an ideal 50-ohm resistive load.
Circuit Board Descriptions
There are eight basic circuit boards plus two power amplifier modules in the ALS-1306. The text below gives a
brief description of each board’s function.
2KWF6
The 2KWF6 is a high-power low-pass filter. It is the very large topmost board with several large toroids and air
wound inductors. This board contains filter SWR fault detection, power amplifier imbalance detection, and
multiple high-power low-pass 5-pole filters. Additionally, the antenna relay board
RLY
attaches directly to the
2KWF6 board.
BS2
The BS2 is located behind the
BAND
switch. It provides all band selection functions, as well as band
indicators.
CB2
The CB2 is located near the front of the amplifier just behind the meters. The CB2 control board provides most
control functions. This includes bias, fan speed, overload and wrong-band protection, and transmit-receive relay
sequencing. It is the hub for nearly all functions, including external interfaces, power metering and 12-volt
busses.
MB1
The MB1 is located behind the front panel below the meters. It contains peak-envelope-power detection
circuits, multi-meter switching, fault indicators, and ALC circuitry. There are four power meter adjustments on
this board; forward power, reflected power, forward peak hold time, and reflected peak hold time. Shunts on a
header located on the board’s upper edge adjust panel meter brightness.
PAM-606 (power amplifier module) Boards
PAM boards are located on top of the heatsinks under the filter board shield panel. The PAM boards, along with
heatsinks, are integral units of the PAM’s. There are no user adjustments on these boards, and the FET’s and
assemblies are gain matched at the factory. The PAM’s are accessed by lifting the filter board (and sheet metal
it rests upon) and folding it over.
PD8
The PD8 is located on the right side of the amplifier just above the panel containing the cooling fans. It contains
a power splitter and two 5 dB attenuator pads. The splitter and attenuator pads isolate the two power amplifiers
from each other, and terminate the PA inputs in 50 ohms over a wide range of frequencies. This is necessary to
stabilize the PAM’s. Do not modify, remove, or bypass the attenuators.
ALS-1306 Exihibit VIII Page 16 / 27
