About the Microwave Oven Waveguide and Magnetron RF Capacitors

THE COMPLETE MICROWAVE OVEN SERVICE HANDBOOK: Operation, Maintenance, Troubleshooting and Repair

Chapter Seven: The High-Voltage System (continued)

very high. The electromagnetic oscillations produced in the resonant cavities are intercepted by the antenna, which then couples the energy into a waveguide.

7.3.3 The Waveguide

Microwave energy cannot travel through a solid conductor, so the antenna radiates the RF power into a waveguide. The waveguide, a hollow metal tube (Fig. 7-8), transports the microwave energy into the oven cavity. Most microwave ovens use a rectangular shaped waveguide, through which the waves of energy travel by reflecting from side to side in a zigzag pattern.

7.3.4 RF Capacitors

In order to prevent small amounts of RF current from backfeeding down the magnetron tube filament leads, which would cause excessive radio and television interference, by-pass (or RF) capacitors and ferrite rings are added to the magnetron assembly (Fig. 7-9). By-pass capacitors filter off any backfeeding current to ground. The ferrite rings are magnetic and oppose high-frequency current flow.

7.3.5 Cooling Fins

Other features of the magnetron structure are the cooling fins, which dissipate the tremendous heat generated by an oscillating magnetron, usually maintaining an operating temperature of about a 260 deg. F (86^deg.C).

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