A maser amplifier operating at the higher harmonics of the cyclotron frequency is presented. Detailed study of the performance has already been done incorporating an axially slotted rectangular waveguide and the study is now concentrated on the detailed experimental construction of the unit. The present harmonic maser also known as a gyrotron will be initially experimentally demonstrated and verified at the X-band frequencies. The goal is using the experience gained from the lower frequency operation is to design, construct and demonstrate a rectangular high harmonic maser amplifier at the W-band frequencies.