  The design and performance of a low-noise, modular cryogenic probe,
applicable to a wide range of measurements over a broad range of working
frequencies, temperatures, and magnetic fields is presented. The design of the
probe facilitates the exchange of sample holders and sample-stage amplifiers,
which, combined with its characteristic low transmission and reflection loss,
make this design suitable for high precision or low sensitivity measurements.
The specific example of measuring the shot noise of magnetic tunnel junctions
is discussed. We highlight various design characteristics chosen specifically
to expand the applicability of the probe to measurement techniques such as
nuclear magnetic resonance (NMR).
