transmitter attenuation [3 dB]
o1	50 Hz off resonance of CHCl₃ signal
p1	90° ¹H transmitter pulse
d1	1 s
rg	receiver gain for correct ADC input
ns	1

First set the offset on resonance of the chloroform signal, and set the instrument in the mode to display both quadrature channels of the receiver. Record an FID and, in your pulse program, change the transmitter phase (or on recent instruments the corresponding phase correction parameter) so that only the left quadrature channel receives a signal. Then set the offset 50 Hz off resonance and repeat the experiment. The left quadrature channel will display a cosine FID whereas the right channel will display a sine FID. Transform this FID and adjust the processing phases for absorption. Now change the transmitter phase in 90° steps and observe the changes on both FID channels and on the spectrum. Repeat this procedure, but leave the transmitter phase unchanged and cycle instead the receiver phase. In a final experiment use two transients and observe the adding of the FIDs. Then introduce a 180° transmitter or receiver phase shift for the second transient in your pulse program and observe the subtraction of the FIDs.

5. Processing

Use standard 1D processing (see Exp. 3.1) applying an exponential window with a line-broadening factor lb = 1 Hz. Adjust the phase of the first spectrum for pure absorption and always use the same phase correction.

FID quadrature channels and transformed spectra for four phases