用于微波频率的许多电子管(如灯塔管)的电性能要求其零件的几何尺寸必须有很细小的间隔的平行平面。栅极结构通常是一连串平行的细丝粘在平坦的框架上。在工作时从阴极来的直接幅射或栅极本身的能量耗散加热了栅丝。栅极的受热会引起尺寸的变化。如果栅丝是在终端固定的,长度的增加会造成弧形及改变电特性。如弧形很厉害的话,会造成短路。要克服这困难,就应在有张力的条件下把 The electrical properties of many tubes used for microwave frequencies, such as beacons, require that the geometry of their parts must have parallel planes with very small intervals. The gate structure is usually a series of parallel filaments glued to a flat frame. The direct radiation from the cathode or the energy dissipation of the grid itself at work heats the grid wire. The heating of the grid can cause dimensional changes. If the wire is fixed at the terminal, an increase in length will cause arcing and change electrical characteristics. If the arc is very powerful, it will cause a short circuit. To overcome this difficulty, we should put it under tension