Masers, the microwave analogues of lasers, have seen a renaissance owing to
the discovery of gain media that mase at room-temperature and zero-applied
magnetic field. However, despite the ease with which the devices can be
demonstrated under ambient conditions, achieving the ubiquity and portability
which lasers enjoy has to date remained challenging. We present a maser device
with a miniaturized maser cavity, gain material and laser pump source that fits
within the size of a shoebox. The gain medium used is pentacene-doped in
para-terphenyl and it is shown to give a strong masing signal with a peak power
of -5 dBm even within a smaller form factor. The device is also shown to mase
at different frequencies within a small range of 1.5 MHz away from the resonant
frequency. The portability and simplicity of the device, which weighs under 5
kg, paves the way for demonstrators particularly in the areas of low-noise
amplifiers, quantum sensors, cavity quantum electrodynamics and long-range
communications