Oboe (navigation)

Over the course of the month the system was used with great success to mark targets for the Main Force against the German industrial center of the Ruhr and for attacks against Cologne.

These missions to northern France allowed Oboe to again demonstrate its value in the precision delivery of markers or bombs, regardless of weather or the visibility of the target.

The Germans pioneered this approach with operational systems like Lorenz beam and X-Gerät that used two narrow beam-like signals that crossed at a point in the sky to indicate a target using triangulation.

Later, during The Blitz, the Germans introduced Y-Gerät, which combined a single Lorenz beam with a transponder-based distance measurement to fix locations.

It could be used anywhere within line-of-sight of the transmitter stations in the UK, and generally provided a reasonable signal up to about 500 kilometres (310 mi), depending on the aircraft's altitude.

However, in these early days of the cathode-ray tube (CRT), such displays were extremely expensive and very long, which made them unsuitable for fitting to a large number of Bomber Command aircraft.

The aircraft would then use conventional navigation techniques, dead reckoning or Gee if it was equipped, to place itself some distance north or south of the target on a point near this line.

As the bomber approached that predetermined range they would first call out a "heads up" to tell the bomb aimer to begin the run, and then a second signal at the right time to drop it.

This was similar to the beam systems like Lorenz, which the UK aircrew were already familiar with using as a blind landing aid in the pre-war period.

One of the most obvious is that any given ground station could only track a single aircraft at a time, compared to Gee where any bomber could pick up the signals from the UK and carry out the necessary calculations.

[8] A more worrying concern was that the bomber aircraft would have to fly straight and level along a gently curving path while the ground station monitored its range as it flew towards the target.

In early testing in September 1941, an aircraft flying along the arc 130 kilometres (81 mi) from Dover demonstrated an accuracy of 50 metres (160 ft), better than any bombing method then in use.

[10] At that time there was a great debate taking place in Bomber Command over the use of "pathfinders", specialized aircraft and crews that would find the targets and use flares to mark them for attack.

Having faced opposition before, the addition of Oboe upset the argument against the specialist role, and what would become Pathfinder Force began forming over the ongoing objections.

[11] The first experiments with Oboe in a combat setting over Germany began on the night of 20/21 December 1942, when a small force of six Oboe-equipped Mosquitoes were sent to bomb a power station at Lutterade in the Netherlands, on the German border.

A follow-up reconnaissance mission the next day showed that nine of the bomb craters could be identified, all of them clustered closely together but some 2 kilometres (1.2 mi) away from the target.

However, it was soon realized that something very odd was occurring; aircraft were dropping only 6 to 10 bombs, often through heavy cloud cover, and having 80 to 90% of them hit their targets, normally blast furnaces or power stations.

Over the UK Oboe demonstrated accuracy on the order of tens of metres, but over the Continent the early tests always produced worse results.

The solution to this problem was provided by the Germans themselves; before the war they had made an effort to calibrate the two systems in a series of cross-Channel measurements that the UK Ordnance Survey also received.

[17] Oboe missions were clearly identifiable to German radar operators; the aircraft would start some distance north or south of the target and then approach it on an arcing path they referred to as "Boomerang".

A system set up at the Maibaum tracking station in Kettwig broadcast false dot and dash signals on the 1.5 m band, hoping to make it impossible for the pilot to figure out if they were at the right position.

The Germans were well acquainted with the British microwave systems in the 10 cm area, but in April 1944 the RAF had already introduced Oboe Mk.

[18] By this point the Battle of the Ruhr was long over and the majority of the RAF's bombing efforts concentrated on targets that were too far into Germany to be visible to Oboe.

Late in the war, Oboe was used to assist food drops to the Dutch still trapped under German occupation, as part of Operation Manna.

Oboe used two stations at well-separated locations in England to transmit a signal to a Mosquito Pathfinder bomber carrying a radio transponder.

The Mark I Oboe was derived from Chain Home Low technology, operating at upper-range VHF frequencies of 200 MHz (1.5 metres).

[9][20] The basic idea of Oboe came from Alec Reeves of Standard Telephones and Cables Ltd, implemented in a partnership with Frank Jones of the Telecommunications Research Establishment (TRE); also part of the team was Dr Denis Stops, who later became a leading physicist at University College London.

[21] Denis Stops' role in the development of Oboe was so secret that he was drafted into the RAF Pathfinder Squadron as a Wing Commander to conduct his work.

[citation needed] The Germans improvised a system conceptually similar to Oboe, code named Egon, for bombing on the Eastern Front on a limited scale.

Oboe appears as a plot point in the "Lost Sheep" episode of the BBC television series Secret Army, which featured the search for a downed airman with technical knowledge of the system.