User Manual

AMPLIFIER CONTROLLER BOARD REV.5
PUB12-030 Rev. 1 Feb 14, 2013 12-030-8 Amplifier Controller Board Rev.5
The AGC circuit then compares this reference voltage to the actual voltage that is produced from the forward
power RF detector. If there is a difference, this is amplified by a high gain OpAmp and this error voltage is fed out
to connector J10. An external cable connects J10 to the attenuator on the RF preamp mounted on the heatsink.
This will lower the drive to the amplifiers until the transmitter power level agrees with the AGC reference voltage.
Note the AGC voltage from the LCD, if it is near to a value of 0 (i.e., under 0.1V), then there is no AGC action left
and the power cannot be raised any further. If the amplifier power is under 100%, then check the RFL power level
and CUTBACK voltage to verify that the amplifier is not reducing power to protect from a VSWR condition.
The cutback circuit checks the level of reflected power as displayed on the LCD screen above [RFL=00.1%]. If
this reflected power is greater than 1%, the cutback circuit automatically reduces the amplifier forward power to
protect the devices. This indicates a mild VSWR condition such as may be caused by an icy antenna. The
cutback function is a safety protection and is therefore permanently in circuit and cannot (or should not) be
disabled. If the VSWR condition worsens such that reflected power exceeds 10% of forward power, the MXi shuts
the transmitter down.
The MXi has built-in VSWR protection to prevent damage to the amplifier from excessive power being reflected
back from the output system. This VSWR protection becomes operational when reflected power exceeds 10% of
forward power. The system shuts down the amplifier for a few seconds and then tries to restart again. This is
done to check if the VSWR was a temporary condition that could have been caused by a lightning strike nearby.
The LCD shows the TRIP status light on the third row of the LCD to indicate that a VSWR trip had occurred. If the
condition persists such that three VSWR trips occur within 1 minute, the system completely shuts down. The LCD
will then illuminate the L/O (Lockout) status light on the LCD to show that a Lockout has occurred.
2.5 INTERLOCKS
Interlocks on the MXi amplifier can be divided into two different types: hard interlocks that shut down the amplifier
without any CPU intervention and soft interlocks that are generated by the CPU chip in response to abnormal
system parameters.
2.5.1 Hard Interlocks
There are hardware interlocks that directly affect the ON/OFF relay K1 by removing the +12V arming voltage on
its coil and preventing it from turning on. There are four of these interlocks as follows:
2.5.1.1. Amplifier Thermal
Heatsink thermal opens if heatsink temperature is too high. Dry Contact across Connector J9 pins 5 and 6.
2.5.1.2. External #1
Interlock supplied for customer use such as RF system interlock or RF Load.
Dry Contact across Connector J9 pins 1 and 2.
Parallel contact provided across J6 pins 14 and 15, only one of J6 or J9 is required.
If not used, then this contact should be shorted out externally.
2.5.1.3. VSWR Relay K2
Contact from VSWR Trip relay K2 pins 11 and 13.
Contact will be closed (OK) if there is no VSWR condition.
Contact will open whenever a VSWR is detected.
Note: Jumper E17 disables this interlock, this is for setup only.