AR 10046246, Operating And Service Manual

Page: 25 / 46

Rev B 7
2. OPERATING INSTRUCTIONS
2.1 GENERAL
Operation of the Model 125A250 broadband amplifier is quite simple. The amplifier’s input signal, whether
swept or fixed in frequency, is fed into the jack marked RF INPUT, and the amplifier’s output signal is taken
from the jack labeled RF OUTPUT . The unit is turned on by activating the front panel POWER switch. In
the event of a major malfunction, protection is provided by a circuit breaker located on the unit’s rear panel.
CAUTION:
The Model 125A250 Amplifier is typically not critical in regard to source
and load Voltage Standing Wave Ratio (VSWR) and will remain
unconditionally stable with any magnitude and phase of source and load
VSWR. However, placing the amplifier in the operate mode without a load
connected to the output connector is not recommended
. It has also been
designed to withstand, without damage, RF input power levels up to
twenty (20) times its rated input of 1mW. However, signal levels higher
than 20mW or transients with high peak voltages can damage the
amplifier. Also, accidental connection of the Model 125A250’s output to
its input (either through direct connection or parasitic feedback paths)
will cause oscillations that may permanently damage the unit’s input
transistors.
The 125A250 RF power transistors are protected from over temperature by sensing the chassis temperature
near the RF output transistors. In the event of a cooling fan failure or an airflow blockage, the DC voltage will
be removed from the RF stages, when the chassis temperature reaches approximately 70°C.
Normal operation can be resumed after the chassis temperature drops below 70° C.
2.2 AMPLIFIER FRONT AND REAR PANELS
Figure 2-1 shows the front panel of the Model 125A250 Broadband Microwave Amplifier. Figure 2-2 shows
the rear panel of the Model 125A250 Broadband Microwave Amplifier.
Figure 2-1. Model 125A250 Front Panel