X band
H2X differed from the original H2S primarily in its X band 10 GHz operating frequency rather than H2S' S band 3 GHz emissions. This gave H2X higher resolution than H2S, allowing it to provide usable images over large cities which appeared as a single blob on the H2S display. The Royal Air Force (RAF) initially considered using H2X as well, but would instead develop their own X band system, the H2S Mk. III. The RAF system entered service in late 1943, before the first use of H2X in early 1944.