The PPA100 from Inmet by Spectrum Control is a flanged attenuator series that operates from DC to 500 MHz. The attenuators are available with attenuation values from 1 dB to 20 dB with an accuracy of +/- 0.5 dB and can handle up to 100 W of power. They matched to 50 Ohms and have a VSWR up to 1.50:1.
