Magnetic recording noise

T. C. Amoldussen and co-workers, eds.. Noise in Digital Magnetic Recording World Scientific Publishing Co., Singapore, 1992. 

The most fundamental aspect of a sensitivity discussion of remote detection is the fact that it is inherently a point-by-point technique. Each spectrum recorded by the detector does not contain any information other than its amplitude. Conceptually, a remote NMR experiment is very similar to a 2D NMR experiment with a z filter between encoding and detection, which causes all transverse magnetization to dephase. For 2D NMR experiments, it has been shown that the signal-to-noise ratio (SNR) per square root time, which will be denominated as sensitivity in the following, is the same as in the ID case when neglecting T2 relaxation [20, 21]. To compare the sensitivity of a remotely detected spectrum [Figure 2.6.4(b)] with an equivalent experiment with direct detection [Figure 2.6.4(a)], we can use an expression similar to the discussion in Ref. [20] ... 

Figure 14 illustrates a recorder curve of the resonance absorption derivative of F for a sample containing 2.7 wt. % of fluorine. The time of scanning the magnetic field through resonance was 2 hours and the time constant of the spectrometer was 90 seconds in order to increase the available signal-to-noise ratio. The F resonance absorption was examined in the concentration range of 0.3 to 12.5 wt. % fluorine. 

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