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In laboratory experiments related to space plasma physics it is often desirable to produce plasmas with characteristics as close as possible to various naturally occurring plasma regimes. In the near‐earth region space plasma densities typically vary from 103–107 cm-3 and temperatures range from a few tenths of an eV to the order of 1 eV. The plasma parameters of electron density, electron temperature, and ion species are primary variables which are often not easy to reproduce in a chamber environment which is dependent upon conventional gas discharge or arc sources for plasma production. A simple microwave discharge device was developed which is easily tunable and capable of producing the moderate range of electron densities without an external magnetic field. The Asmussen‐type microwave plasma source described here covers and exceeds the parameter ranges required, is relatively easy to construct, and is inexpensive. The device makes use of an air dielectric coaxial coupler to couple magnetron output to a resonant cavity. Estimates of effective electric fields and source densities and temperatures suggest that similar devices can easily be constructed and fashioned to produce these parameters, depending upon requirements, over a wide range of values. The use of widely available commercial magnetrons manufactured for microwave ovens allows a certain ease in the construction of these devices in that available cavity Q’s can range to lower levels and therefore resonant lengths can be adjusted more easily. The design is discussed relative to desired experimental parameter ranges and some discussion is given of expected source current densities, electric fields, and temperature ranges.