MXD5U OPERATIONS AND MAINTENANCE
3
3.1
AMPLIFIER INSTALLATION AND STARTUP
The transmitter can be fully operational with minimal setup when turned ON. However, a good practice is to take
the “start from scratch” approach, which means that you should take precautionary measures before the amplifier
is allowed to run at full rated power. These important steps will avoid any catastrophic failures at start-up. The
procedure described is essentially the same approach taken at the factory with a new and untested transmitter.
This also applies if there is a need to completely replace a major sub-assembly in the transmitter.
B
EFORE
A
PPLYING
AC
TO THE
U
NIT
Pay careful attention to items 1 to 3 before applying AC to the amplifier. These are initial steps that
must
be
observed and followed for proper and safe operation of the amplifier.
1. Termination
•
Ensure
that
the amplifier is properly terminated with a suitable load. This can be into a dummy load or into
the transmitter output system. A 50 Ohm, 20W load with at least 20dB return loss (1.2 VSWR) is
recommended. Preferably, directional couplers with known coupling levels at the frequency of interest
should be connected at the output of the band-pass filter. These points are very useful in determining
absolute power levels and losses and for use as an RF sample for monitoring purposes. An RF sample
test point is provided below the RF out on the front panel. Its coupling is approximately 24dB and it is not
calibrated for exact measurements.
2. Interlocks
•
Interlocks are employed by the amplifier to avoid damage to the equipment and to the output section. For
instance an internal interlock for over-temperature exists to shut down the Transmitter if the temperature
of the amplifier heatsink exceeds a certain critical level. An Interlock which is external to the transmitter
can be used through the INTK terminal block located on the rear panel. This may be used in cases where
external transmitter switching is desired. If no system external to the transmitter requires the use of the
interlock contact terminals, replace this interlock connection with a jumper across the terminals.
Figure 7 Rear Panel Showing Interlock Terminal Board
3. Power At Minimum
•
Initially, the RF drive applied to the amplifier should be preset at minimum level. Adjust the OUTPUT
LEVEL control on the Modulator or Translator for a minimum output. Adjustment of the RF output power
of the amplifier is performed through the remote interface.
3.2
3.3
A
PPLYING
AC
TO THE
U
NIT
•
Check that the AC voltage available to the amplifier is within the range of 90-264VAC. If so, proceed to
applying the power to the AC INPUT of the amplifier
•
Once the AC is applied to the unit, the +28VDC Power Supply turns ON supplying power to the
Controller.
B
EFORE
T
URNING THE
A
MPLIFIER
ON
Check that all of the following conditions are met:
PUB09-03 Rev 0 April 16, 2009
09-03-9
MXD5U Operations and Maintenance
