User Manual

MXi AMPLIFIER CONTROLLER BOARD REV.2
PUB06-82 Rev 1 July 17, 2007 06-82-29 MXi Amplifier Controller Board Rev.2
At this point, the operator should proceed to verify cutback and VSWR trip functions, as described in the next two
sections.
4.2 AGC AND CUTBACK PROTECTION
Before the operator attempts to set up the AGC or cutback circuitry, the forward and reflected power levels must
be properly set up to calibrated levels as described in Section 4.1.
4.2.1 AGC Setup
The AGC is simply set up using the Amps submenu that is accessed from the Main menu of the LCD. A view of
this submenu is given the below. The operator just needs to press the AGC+ button on the touchpad to increase
the power or the AGC- button to decrease the power. The top line of the LCD displays the current level of the
FWD power. This AGC level will be saved even after AC power outages. If the RF power is nil or very low, make
sure that the RF drive has been enabled by pressing the RF On button on the touchpad
Figure 17 Amps Submenu Screen
4.2.2 Cutback Setup
To set up the cutback level, a power sample must be fed into the reflected power connector of the MXi board that
is –16dB down from the forward power sample level. The most convenient way to accomplish this is to take this
sample from the RF monitor port on the rear of the transmitter chassis.
1. Disconnect the AGC control connector J10 from the MXi board to remove any possible AGC or cutback
action while verifying the Reflected power. If the forward power is greater than 100%, adjust the output
level of the upconverter until it is at 100% (+/- 2%).
2. Attach an RF cable from the RF monitor connector at the rear of the MXi control chassis and insert a
–16dB pad. This pad can consist of a –10dB and –6dB pad in series. Remove the RF cable from J13 that
comes from the output coupler and attach a cable from the –16dB pad off the forward monitor sample.
3. We are assuming that the coupling level from the monitor connector is the same as the coupling level for
the forward power RF coupler. To verify this by checking the RFL power level on the LCD, it should read
around 2.5% power. If it is off by more than 0.5%, adjust the amount of padding until the RFL power
reading is within the range of 2% - 3%. A variable attenuator pad would be ideal for this application.
4. Readjust the upconverter output level so that the forward power reads 110% again.
5. Also disconnect the cable from the monitor port for now.
6. Reconnect the AGC control connector J10 on the MXi board.
7. Reconnect the cable from the monitor port to the reflected power sample at J13.
8. Adjust the potentiometer R105 until the forward power reading is about 96% - 98%, which puts the
system just at the edge of cutback.
The setup is now complete, remove the monitor cable from J13 and attach the output coupler back to J13.
4.3 VSWR PROTECTION
The VSWR protection does not really need any setup or calibration since it is fixed to trip when the reflected
power is –10dB of the forward power level. To verify the VSWR trip function, the following steps must be taken.