This paper is devoted to the experimental investigation of a new class of s
uperconducting microwave oscillators based on Cherenkov radiation from Jose
phson vortices. Samples consisting of a long Josephson junction embedded in
a dispersive transmission line with space-periodical inhomogeneities were
fabricated and tested. We report observation of new resonances on the I-V c
urve of the system and present the first radiation measurements in the 80 -
120 GHz frequency range.