These designs utilize silicon bipolar devices as the negative resistance generator. The frequency of operation is determined by a varactor diode that serves as a voltage variable capacitor. Silicon hyperabrupt varactors offer the lowest phase noise performance. Careful selection of the varactor diodes manufactured in-house provide linear monotonic tuning characteristics requiring only simple external driver circuits. This range of VCOs is constructed using discrete chip device integrated onto a conventional alumina substrate or on a Glass Microwave Integrated Circuit (GMICTM). This is packaged into standard outline TO-8 packages. These packages are hermetically sealed using resistance weld techniques. This compact rugged construction allows for simple installation on either through hole or surface mount PCB, and finds a wide range of applications in demanding military, hi-rel and commercial systems.