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SECTION 6.0
AUTOMATIC LEVELING CONTROL (Optional)
6.1 ALC FEATURES
The Automatic Leveling Control ( ALC ) switch located on the front panel has three positions, 'INT',
'OFF' and 'EXT'. Described below are the features of each position
Important Note:
Figures 5.0 and 6.0 indicates the display for a typical amplifier and the ALC
option is indicated however if the amplifier is not equipped with this option, the ALC option will not
be displayed.
6.1.1 The 'INT' Position
The 'INT' or Internal position enables the amplifier to automatically level on an RF power level
selected by an operator displayed on the Forward Power reading located on the Front Panel LCD
display. Using the 'INT' feature, no external sources are required for leveling control and the
operator determined power level will be automatically maintained even though the frequency or input
signal levels might change. Refer to Paragraph 6.2 for the procedure to operate the amplifier in the
'INT' mode.
6.1.2 The 'OFF' Position
The 'OFF' position enables the amplifier to operate in a passive mode with no automatic features
controlling input drive levels or output power levels. In this mode, the operator has full manual
control of the amplifier including the input signal gain, frequency and power output. As a result, the
operator must be fully knowledgeable of the effects of these variables in relationship to the operating
characteristics of the amplifier. With this in mind, the two most important factors are the dB flatness
of the amplifier over the operating frequency range and the rated output power of the amplifier.
Depending on the response curve provided on the S21 Parameter Plot for the amplifier flatness,
which is located within Appendix A, and the size of the frequency steps of the signal generator can
increase or decrease the power level by as much as 4 dB. This is the result of the design tolerance of
the amplifier to operate within a ± 2 dB over the rated frequency range. A ± 2 dB tolerance means
that the maximum deflection from minimum to maximum of the flatness curve can represent a delta
change up to 4 dB. With this factor in mind, it is advisable to identify the specific frequencies that
represent the greatest change from the nominal 0 dB level and adjust the input signal accordingly in
so that the amplifier is not over driven beyond the rated power specification. Taking these
precautions will prolong the reliability on the amplifier.
