A high frequency filter kit in which resonating first and second electrical circuits are enclosed between proximal and distal ends of a filter case. Partitioning the inside of the enclosed resonant circuits may be performed by a user to form at least a first cavity and a second cavity. The first resonating circuit is then disposed inside the first cavity of the filter case extending from the proximal end towards the distal end, and the second resonating circuit is disposed inside the second cavity also extending from the proximal end towards the distal end. Electrical signals are coupled into the resonating circuits by an encased signal coupler which is removably mounted by a coupling housing for supporting the signal coupler at the proximal end of the filter case for positioning in the vicinity of the resonating circuits. The kit thus facilitates enhanced turnout time and communication of design specifications for manufacture by specifying the basic components required to build the specific high frequency filter, allowing the user to build prototype filters that may be used for manufacturing a RF/microwave system or be provided as a sample to the filter manufacturers.