RDF techniques. Researchers had set up the antenna in 1919 but had been neglecting it in favour of smaller designs. These were found to have very poor performance due to the electrical characteristics of the Slough area, which made it difficult to determine if a signal was being received on a straight line or down from the sky. Smith-Rose and Barfield turned their attention back to the Adcock antenna, which had no horizontal component and thus filtered out the "skywaves". In a series of follow-up experiments they were able to accurately determine the location of transmitters around the country. It was Watt's continuing desire to capture the location of individual lightning strikes that led to the final major developments in the basic huff-duff system. The lab had recently taken delivery of a WE-224 oscilloscope from Bell Labs, which provided easy hook-up and had a persistent phosphor. Working with Jock Herd, in 1926 Watt added an amplifier to each to the two arms of the antenna, and sent those signals into the X and Y channels of the oscilloscope. As hoped, the radio signal produced a pattern on the screen that indicated the direction of the strike, and the slow-decay phosphor gave the operator ample time to measure it before the display faded. Watt and Herd wrote an extensive paper on the system in 1926, referring to it as "An instantaneous direct-reading radiogoniometer" and stating that it could be used to determine the direction of signals lasting as little as 0.001 seconds. The paper describes the device in depth, and goes on to explain how it could be used to improve radio direction finding and navigation. In spite of this public demonstration, and films showing it being used to locate lightning, the concept apparently remained unknown outside the UK. This allowed it to be developed into practical form in secret. Battle of Britain During the rush to install the Chain Home (CH) radar systems prior to the Battle of Britain, CH stations were located as far forward as possible, along the shoreline, in order to provide maximum warning time. This meant that the inland areas over the British Isles did not have radar coverage, relying instead on the newly formed Royal Observer Corps (ROC) for visual tracking in this area. While the ROC were able to provide information on large raids, fighters were too small and too high to be positively