环形背槽
在变幅杆螺柱端面上加工的一条与螺柱轴线同心的窄环形凹槽。该凹槽的内径始终大于相配增幅杆的直径。
它用于降低圆柱形变幅杆中非轴向谐振的谐振频率，在某些情况下还用于减少增幅杆—变幅杆连接处的咬粘。
另见背槽。
Circular back slot
A narrow, circular groove machined on the stud surface of a horn that is concentric with the stud axis. The groove's inside diameter is always larger than the diameter of the mating booster.
It is used to lower the resonant frequencies of nonaxial resonances in cylindrical horns and, in some cases, to reduce galling at the booster-horn joint.
Also see back slot.