Flap attenuator

Schematic of a flap-type waveguide attenuator:
1) resistive cord, 2) slot in waveguide, 3) adjusting knob, 4) dial, 5) reduction gear 4:1

The flap attenuator is a flap-type waveguide attenuator that allows for precise and continuous attenuation of electromagnetic waves traveling through a rectangle waveguide.

It comprises a thin, disk-shaped attenuation material that extends through a longitudinal slot in the middle of the wider side of the waveguide into the inner space of the waveguide. The extent of the insertion is variable, and the attenuation can be made approximately linear with the insertion by properly shaping the resistance card.

The attenuation can be up to 50 decibels.