High-amplitude broadband

The overall energy from the filtered broadband plotted against measurement location provides an approximation of the mode shape of the installed machine. Figure 44.31 illustrates a vertical broadband plot taken from a Spencer blower. Note that the motor appears to be flexing in the vertical direction. Extremely high amplitudes are present in the motor s outboard bearing and the amplitudes decrease at subsequent measurement points across the machine. 

The power divider is a broadband multi-port device which permits the rf inserted in one port to be equally divided between the outputs. The outputs have the same phase and the same amplitude and are highly isolated from each other. Conversely, if two rf signals are put into the output ports of the power divider, they will be added vectorially. Hence the... 

An improved variant of the popular double cross-polarisation (DCP) experiment for heteronuclear dipolar re-coupling in solid state NMR spectroscopy under MAS was introduced by Bjerring and Nielsen. By simple phase and amplitude modulation of the RF irradiation at the Hartman-Hahn sideband conditions, the new pulse sequence, dubbed iDCP, was shown to enable broadband excitation with the high efficiency of y-encoded coherence transfer. The efficiency and robustness of iDCP towards isotropic chemical shift variations and chemical shift anisotropies in the case of uniformly C, N-labelled proteins has been demonstrated numerically and experimentally by N to C coherence transfer for N-labelled N-Ac-L-valyl-L-leucine and C, N-labelled-L-threonine. 

Usually, ions of tn/z 69 and 414 from the calibration chemical PFTBA are used to find the values for the two parameters, A and B. The trapping frequency calibration is carried out near = 0.845 at a fixed RF trapping field. A linear relation between q xm and RF c is true only under ideal conditions but, as a first-order approximation, it works well for this two-step isolation method in a non-ideal quadrupole ion trap. Typically, in an ion trap for which the oscillation frequency of the RF potential is 1 MHz, the frequency error of the calibration is less than 1 kHz, which corresponds to an error of < 1 Th in the high-mass isolation step. The amplitude of the broadband waveform is determined empirically by the manufacturer and can be accessed by users. 

---