Operating Manual Vol 1 - ES Documentation

RF LevelSMIQ2.5.2 Interrupt-free Level SettingIn the ATTENUATOR MODE FIXED and ATTENUATOR MODE ELECTRONIC operating modes, levelsettings are carried out without interruption. The attenuator is switched electronically rather thanmechanically.The MODE FIXED variation range is somewhat over 20 dB, the variation range of MODE ELECTRONICover 90 dB. In case of over- or underranging of the normal variation range, level errors strongly increaseand an under/overrange warning is displayed. At high attenuation values the spectral purity of the outputsignal is degraded.The ATTENUATOR MODE ELECTRONIC mode is only possible with level control switched off. TheALC OFF mode is automatically set to TABLE.Note:To ensure highest level accuracy in ATTENUATOR MODE ELECTRONIC mode, the selfcalibration routines ALC TABLE and LEV ATT should be called up in the UTILITIES -CALIB menu after temperature variations of more than 5 degrees.The MODE ELECTRONIC cannot be used either simultaneously with the SLOTATTENUATION function of the digital standards. This applies to all TDMA standards. TheMODE ELECTRONIC cannot be used either simultaneously with the DIGITAL MOD -POWER RAMP CONTROL - ATTENUATION function.2.5.3 Switching On/Off Internal Level ControlThe LEVEL - ALC menu allows the level control to be switched on and off for special applications. In thenormal operating mode for CW, AM and FM(PM), level control is switched on so that an optimum levelaccuracy is obtained. For vector modulation or digital modulation, level control must normally be off. Inthis case the SAMPLE&HOLD or the TABLE mode can be selected instead.In the SAMPLE&HOLD mode the level is recalibrated after each level or frequency setting. To do this,CW is selected for a short period of time, level control is switched on and the level control held at thevalue attained. If this calibration procedure is not desired, the TABLE mode (level control voltage takenfrom a table) can be selected. In this mode the correction values required after a frequency or levelchange are obtained from a table. With the LEARN TABLE function called up, a new table can beprepared without any additional measuring instruments being required.The preset level control is AUTO. Level control in this mode is automatically adapted to the operatingconditions. For special applications, level control can be held in the OFF or ON state. Level control OFFis useful for improving the intermodulation suppression in multi-signal measurements in the CW mode.The ON setting is recommended if vector modulation or digital modulation with a constant envelopecurve is required.1125.5555.03 2.50E-8