The Magnetron - A Low Noise , Long Life Amplifier

This author; a leading proponent of the transmission of power via microwave beams, describes how the common microwave oven magnetron can be externally locked to provide 30 dB of gain-resulting in a 500 watt, 70% eficient, $15, coherent microwave source. T he 2450 MHz magnetron which supplies 700 watts of average power to the ubiquitous microwave oven is made in a quantity of 15,000,000 units annually at a very low price, less than $15. It has a high conversion efficiency of 70% and small size and mass. What is not generally recognized is that it has very low noise and long life properties, and that it can be combined with external circuitry to convert it into a phase-locked amplifier with 30 dB gain, without compromising its noise or life properties. Such amplifiers are ideal for combining with slotted waveguide radiators to form radiating modules in a low-cost, electronically steerable phased array for beamed power, which motivated this study. However, there are conceivably numerous other practical purposes for which these properties can be utilized. The low noise and long life properties are associated with a feedback mechanism internal to the magnetron that holds the emission capabilities of the cathode to those levels consistent with both low noise and long life. This internal feedback mechanism is effective when the magnetron is operated from a relatively well filtered DC power supply with