The magnetron allowed radar systems to operate at microwave frequencies, which greatly reduced the size of their antennas and made them much more mobile and accurate.

Immediately following the visit, the National Research Council of Canada began development of a GL radar based on the UK design.

III units found themselves relegated to secondary roles, as diverse as artillery spotting, coastal surveillance and weather balloon observation.

The British Army began serious research in radar systems in 1936, after being introduced to the developments made by the Air Ministry at their experimental station at Bawdsey Manor.

The development team, nicknamed the "Army Cell", was set the task of building a system that would provide slant range measurements with an accuracy of 50 yards (46 m) or better.

The Air Ministry's Airborne Group, led by Edward George Bowen, had the problem of desiring antennas small enough to mount in the nose of a twin-engine aircraft.

[4] Given the support for microwave development from both services, Henry Tizard visited the General Electric Company's (GEC) Hirst Research Centre in Wembley in November 1939 to discuss the issue.

Watt followed up with a personal visit some time later, leading to a 29 December 1939 contract for a microwave AI radar set using conventional tube electronics.

[5] Birmingham's Mark Oliphant initially attacked the problem by attempting to further develop the klystron, a pre-war invention that was one of the first successful microwave-frequency tubes.

[7] This led to increasing friction between Philip Dee, who ran the AI team's magnetron efforts, and Rowe, in overall command of the Air Ministry researchers.

On 30 December 1940, Dee commented in his diary that: The GL fiasco has ended up with the whole thing being moved en bloc to BTH, including two AMRE staff.

Although information about the GL system's development continued to flow to Canada, little economic or scientific support was given until 1943 when the NRC greatly expanded its liaison office in London.

Adding to the confusion, by January 1941 the Ministry of Supply gave up on the ongoing Army efforts in the UK and released a new specification for GL based on a magnetron.

Instead, they decided to adopt the solution used for the earlier GL sets, and mount their entire electronics van on a bearing plate and point it in the required direction.

At that time, the chief engineer of Westinghouse proved extremely impressed, and noted to a member of the NRC "that his company would not have believed that what we had done in nine months, could have been done in two years.

The first production example didn't roll off the line at REL until July 1942, by which time it was clear there was an issue and pressure was put on the electronics division to speed up deliveries.

Another issue was that the Canadian designers had added a "velocity laying" system that smoothed out inputs to the control wheels that allowed for finer tracking, but was yet another change to get used to.

Wallace began to talk to people on the shop floor, and was eventually told by one superintendent that Hackebusch personally ordered him to concentrate on quantity rather than quality, so that the systems were not being tested before delivery.

During a visit to Ottawa in March 1943, Phillips met with Mackenzie and Wallace and agreed the problem was real, admitting "all the weaknesses of Hackbusch and [said] they are going to make a fundamental change which we all know is overdue by at least two years.

[22] Adding to their problems, REL was constantly short of magnetrons, which were built by General Electric in the US, CRTs for the displays, or the multitude of other conventional vacuum tubes the system used.

The UK-based APFs formed the backbone of the London-area AA direction during Operation Steinbock in early 1944, the last concerted German bombing effort using manned aircraft.

He was not impressed by anti-aircraft fire, and stated that more German bombers would be destroyed by bombing the homes of the people that manufactured them than any amount that radar-guided guns could hope for.

This version was used as a meteorological system for measuring the winds aloft by launching weather balloons with radar reflectors that allowed them to be tracked for extended periods.

[32] The Royal Artillery's historian records that 'Baby Maggie' originated in the Mediterranean theatre with 62nd Anti-Aircraft Brigade, which commanded the AA units in the Allied invasion of Sicily (Operation Husky).

Improvised from existing Searchlight Control Radar (SLC) components and reduced to bare essentials, its transmitter, receiver, aerial array and operating display were all housed in a single two-wheeled trailer towed by a 3-ton lorry.

III used a somewhat complex multi-cathode ray tube (CRT) display system known as the Presentation Unit, built by The Gramophone Company (EMI).

When the capacitor reached a pre-selected voltage, it triggered a second timebase generator set to 6 microseconds, or in the case of the radar's there-and-back round trip, 1,000 yards (910 m).

The output of this time base was inverted and mixed into the signal on the coarse display, causing a bright extended line to appear along the bottom of the baseline, known as the strobe.

When the radar operator pressed a button, the interrogator would send out periodic signals on the selected frequency via a large whip antenna mounted at the rear corner of the cabin.

Instead of a sharp bell curve like shape, a signal responding to the IFF challenge would have a rectangular extension behind it, allowing the operator to easily see which aircraft were friendly.