  Previous studies have shown that tuning/matching conditions optimized for
transmission and detection can be significantly different for a variety of
commercial NMR probes. In addition, it was also shown that by optimizing
reception tuning (as opposed to typical transmission or reflection tuning) one
may in some cases obtain sensitivity enhancements by as much as 25-50%. In
earlier work, spin-noise and absorbed circuit noise signals have also been used
to characterize reception optima. In this work, we show how the length of the
coaxial transmission line cable between the pre-amplifier and the probe affects
the positions of the reception tuning optimum, the radiation damping strength,
induced frequency shifts, as well as, the shape of the spin-noise and absorbed
circuit noise line shapes.
