User Manual

AMPLIFIER CONTROLLER BOARD REV.5
PUB12-030 Rev. 1 Feb 14, 2013 12-030-13 Amplifier Controller Board Rev.5
3.2 CUTBACK PROTECTION
Before the operator attempts to set up the cutback circuitry, the forward and reflected power levels must be
properly set up to calibrated levels as described in Section 3.1.
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.
3.3 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.
To check the VSWR trips, a power sample must be fed into the reflected power connector of the MXi board that is
–10dB 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. Install a jumper in E17 that will prevent any VSWR trips.
3. Attach an RF cable from the RF monitor connector at the rear of the MXi control chassis and insert a
–10dB pad. 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. 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 over 10.1% power but less than 11% power. Note that a
minimum of 10.1% power is needed to insure a VSWR trip. If the RFL power is under 10.1%, decrease
the amount of padding until the RFL power reading is within the range. If the RFL power is too high (over
11%), increase the amount of padding until it is in the range. 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.