High power microwave (HPM) moderate band (MB) sources combine simple design concepts seen in ultra wideband (UWB) sources but with longer pulses to produces higher energy spectral densities.These factors allows the designs to be more compact and less complicated than many narrowband HPM sources.In this paper we will demonstrate from both simulation and experimental results the operation of a electrically small tunable self-resonant mesoband source utilizing a folded helical antenna as the energy storage and radiating element.The system is based on a previous design for a HPM folded helix antenna that has a resonant frequency of 46 MHz and is charged to 70 kV .The design presented here utilizes a tunable capacitance that allows the resonant frequency to be tuned between 52 MHz and 87 MHz with ka = .58at the lowest resonant frequency.