HP 8360 manual Figure A-2. Typical External Leveling Hookup

NEOFITIVE

DETECTOR

Figure A-2. Typical External Leveling Hookup

ALC Disabled - Leveling Mode ALCoff , Leveling Mode Search

ALC Off. In this configuration, the ALC is disabled, power is not sensed at any point, and therefore the absolute power level is uncalibrated (see Figure A-l). Direct and separate control of the RF modulator (p/o RF Components) and the attenuator is possible. The synthesizer’s front panel indicates the attenuator setting and

a reference level. The reference level is an approximate indication of the attenuation provided by the RF modulator . Typically the RF amplifier that follows the modulator is saturated for modulation levels near 0 dB. Therefore the actual change in the RF output power will not track the indicated reference level until the amplifier is out of saturation.

The ALC off mode is useful for applications that involve pulse modulation with extremely narrow pulses. If the pulse is narrow enough, the ALC may be unable to provide accurate leveling due to bandwidth limitations.

Search. Search mode is similar to the ALC off mode in that, the ALC is disabled in order to remove bandwidth limitations. The essential difference is that, when search mode is enabled, the synthesizer searches out the appropriate modulator level such that the RF output power after the ALC is disabled closely matches the power prior to search mode being enabled. Specifically, when search mode is selected the synthesizer follows this sequence of steps:

1.All modulation is disabled and the ALC system is closed to provide a calibrated reference power.

2.The output power is measured using the internal coupler/detector.

3.The ALC system is disabled (opened).

4.While monitoring the internal detector, the RF modulator level is varied until the detected power is equivalent to the reference power measured in step 2.

A-8 Operating and Programming Reference	HP 8360
User’s	Handbook