H2S (radar)
H2S was the codename for the first airborne, ground-scanning radar system used by the Royal Air Force (RAF) during World War II. The name is believed to be a deliberately obfuscated code, possibly referring to "Height to Surface," "Home Sweet Home," or other similar phrases. Its primary purpose was to allow RAF Bomber Command aircraft to locate and identify ground targets, particularly cities, in all weather conditions, including through cloud cover and darkness.
The H2S radar operated by emitting microwave radio waves downwards towards the ground. These waves reflected off the terrain and man-made structures, and the returning signals were processed and displayed on a cathode ray tube (CRT) screen in the aircraft. This display provided a radar map of the ground below, enabling navigators and bomb aimers to visually identify target areas even when they were obscured from view.
Key features of the H2S system included:
- Microwave Frequency: H2S used microwave frequencies (around 3 GHz), which provided better resolution than earlier radar systems.
- Rotating Antenna: The radar antenna rotated continuously, providing a 360-degree scan of the ground.
- CRT Display: The reflected signals were displayed on a CRT screen, creating a plan view of the terrain below. Brighter areas on the display indicated stronger radar reflections, typically from buildings, urban areas, and water bodies.
- Navigation and Bombing Aid: H2S was a crucial navigation aid, allowing bomber crews to stay on course even in poor visibility. It also allowed for more accurate bombing runs by pinpointing targets even when visual confirmation was impossible.
The introduction of H2S was a significant technological advancement in aerial warfare. However, its effectiveness was somewhat diminished as the German forces developed countermeasures, including radar detectors and jamming equipment. Later versions of H2S incorporated frequency changes and other improvements to counter these countermeasures.
H2S played a crucial role in the strategic bombing campaign against Germany and contributed significantly to the Allied war effort. Its development and deployment marked a pivotal moment in the history of radar technology and its application in military aviation.