TM 11-6625-3053-14
b. Leveling. When the ALC or Automatic Leveling Control switch is turned on, the instrument is capable of
maintaining a given power output over its entire frequency range without manually POWER SETTING. Output levels
may be varied as required.
In this case, the process is called ALC SETTING and is explained in para 2-5 e.
The ALC ckt is part of the Leveling & Modulation ckt or A3 assembly (Item K ). It works in conjunction with the Leveling
Attenuator Assy A5 (Item L ) to control the output at a constant level.
c. Modulation. The AN/USM-213B is capable of modulating the RF OUTPUT signal in four different manners.
The type of modulation is selected by setting the MODULATION switch to the required position. Three types of
modulation are acted upon in the modulation part of A3 assy.
1.
Internal Square Wave Modulation. The square wave signal is generated in the modulation ckt of A3
assy.
2.
External AM Modulation. A sine wave is introduced at front panel AM jack. This signal passes through
a modulation ckt of A3 assy.
3.
External Pulse Modulation. A pulse is introduced at front panel PULSE jack. This signal passes
through a modulation ckt of A3 assy.
All of the above modulating signals are injected at the AT-1 part of the leveling attenuator.
The fourth and last type of modulation is external FM. A sine wave is introduced at front panel FM
jack, goes through a ckt in A2 power supply and then is capacitor coupled directly to the klystron
repeller.
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