In order to check that I have the Solfan Gunn diode correctly tuned to the 10GHz band, I purchased this tuned cavity wave meter. A dip is observed in the detector diode when the cavity is tuned to that of the Gunn diode so you know the exact frequency.
The picture shows a detector diode in its cavity to the left, a Decca attenuator to the right and a small horn antenna on the end of the wave guide.
