- JMC is a world-class supplier of trimmer capacitors, non magnetic variable inductors and microwave tuning elements. JMC offers a wide variety of variable capacitors for RF and microwave applications. Giga-Trim® capacitors are miniature capacitors designed for high resolution tuning of RF power circuits. JMC air capacitors are available in a variety of sizes and mounting configurations incorporating a one piece, self-locking, constant torque drive mechanism. Ceramic trimmer capacitors are available in surface mount, strip-line, and through hole lead styles. Microwave tuning elements are an economical means of tuning waveguides, cavities, and other microwave structures.