[en] The measurement of electron density in the JET pumped divertor by conventional reflectometry techniques is difficult because of poor access to the divertor region, unfavourable plasma geometry and the small plasma size. This paper presents a new reflectometer diagnostic which can operate in the difficult conditions of the pumped divertor. It is a 'comb' reflectometer in which a number of microwave signals with different frequencies are launched simultaneously into the plasma, and the peak electron density along the sightline is estimated by determining which signals are transmitted and which are reflected. The design and operating principles of the diagnostic are described, and preliminary results illustrating its performance are presented. (Author)