Specifications

MXI1002 OPERATIONS AND MAINTENANCE
should normally produce 100% output power immediately. For first time installations, it is recommended that the
level of the modulator be set to minimum initially and then increase in steps until 100% power is attained. This is
done so that catastrophic failure is avoided in the event that something is not connected properly. Keep in mind
that in a newly installed transmitter that loose or bad connections in the output, as an example, is possible
particularly when the output system is not swept for proper matching or VSWR. Hence, as the power is increased,
by observing the combined, single amplifier, reflected, and reject power metering one will be able to assess if
everything is in proper order.
4.4.1 Turning ON the MXi Transmitter
1. Enable amplifier LOCAL operation by pressing the REM touch button such that the REM legend is NOT lit.
• Push the front panel ON button.
• The MXi Amplifier should now be ON.
Figure 6 Transmitter ON
2. Monitor both power supply voltages and currents on the LCD. Check that the power supplies are operating by
pressing the P/S touch button. The voltage readings should be about 50V and the currents should be about
7.7A per Amplifier under Static condition (no RF drive).
ALLOW THE AMPLIFIER SOME WARM-UP TIME!
Only after the transmitter has been ON for approximately 15 minutes should you perform the fine
adjustments. The amplifier must be allowed to reach its operating temperature for stable operation. The
Power Amplifier in the MXi transmitter are equipped with thermal compensation circuits, which reduce the
output power when the temperature rises. Therefore, the operating temperature must be reached before
adjusting the RF level to its proper level, i.e. 100%. The amplifiers are also equipped with Automatic Gain
Control, primarily designed to prevent the transmitter from overpower or overdrive condition.
3. Increase the RF output by slowly turning the Modulator/Exciter or Channel Processor output level control.
Stop at about 25% output power indicated on the LCD. At this level, the current should not be more than 12
Amps per Amplifier.
4. If the current is not drastically higher, increase the power to 50%. Again, make note of the PS current
readings. The current should be less than 25 Amps per Amplifier. Proceed to the next step if this condition is
met.
5. Increase the RF output to 100%. The current should be about 45A per Amplifier with a black video signal.
Typically, with a 50% APL video signal, the current drawn is about 45A per Amplifier.
6. AGC SETTING: With the AGC still disabled, increase the output power to 110%, using the output level control
in the Exciter or Channel processor. Enable the AGC by inserting the AGC jumper, E16, on the control board.
Use the LOWER button on the LCD to set the power to 100%.
7. With the amplifier fully functional and adjusted to its final setting, record keeping becomes very important.
Record the current, voltage, power, etc. This data can be used as a very valuable troubleshooting tool later.
Below is typical test data pertaining to the MXi amplifier at 100% output power..
8. With the amplifiers fully functional and adjusted to its final setting, record keeping becomes very important.
Record the current, voltage, power, etc. This data can be used as a very valuable troubleshooting tool later.
Below is typical test data pertaining to the MXi amplifier at 100% output power.
PUB11-018 Rev 0 July 8, 2011 11-018-7 MXi1002U Operations and Maintenance