Operating Manual Vol 1 - ES Documentation

Analog ModulationsSMIQ2.7.3.1 FM Deviation LimitsThe maximal deviation depends on the RF frequency set (cf. Fig. 2-29). It is possible to enter adeviation that is too high for a certain RF frequency or to vary the RF frequency to a range in which thedeviation can no longer be set. In this case the maximally possible deviation is set and an errormessage is displayed.In the RF range 450 MHz to 750 MHz and 1200 MHz to 1500 MHz a different synthesis range isselected depending on the deviation set. If the deviation is smaller than 500 kHz or 1000 kHz, thesynthesizer is in the normal mode with optimal spectral purity. If the deviation set is larger the I/Q modeis automatically selected.maximalFM-deviation[kHz]2000I/Q modenormal mode1000500Fig. 2-290,3 450 750 1200 1500 3300RF frequency [MHz]Dependency of the FM maximal deviation on the RF frequency set2.7.3.2 PreemphasisPreemphasis results in a preemphasis of the modulation signal with time constants 50 µs or 75 µs. Thehigher frequencies of the modulation signal are preemphasized.When preemphasis is switched on, only 1/4 of the maximal deviation is permissible. The highestpermissible modulation frequency is 15 kHz. Exceeding the permissible modulation frequency can leadto overmodulation."1125.5555.03 2.62E-8