The "AN" version gained a switchable phasing line for the antenna. Switching in the phasing line led to a phase displacement of the antenna's radiation pattern and with that, a squinting to the left or right. This enabled the system in effect to switch from the rather broad "scanning for maxima" to narrow lobe switching. In that mode, a skilled operator could achieve an angular resolution of 0.1°. The "Freya" radar was more advanced than its British counterpart, Chain Home. "Freya" operated on a wavelength (250 MHz) while Chain Home used 12 m. This allowed "Freya" to use a much smaller antenna system, one that was easier to rotate, move and position. It also offered higher resolution, allowing it to detect smaller targets. Because of its complex design, only eight "Freya" stations were operational when the war started, resulting in large gaps between the covered areas. The British Chain Home radar, although less advanced and more prone to errors, was simpler, which meant that the complete Chain Home network was in place in time for the Battle of Britain. "Freya" was often used in concert with the primary German gun laying radar, "Würzburg Riese" ("Würzburg Giant"); the "Freya" finding targets at long distances and then "handing them off" to the shorter-ranged Würzburgs for tracking. Later in the war, "Freya" operated in the band from (120 to 130 MHz), with a pulse width of three microseconds, a peak power output of 15 to 20 kW, and a pulse repetition frequency of 500 Hz. It had a maximum range of only , making it inferior to Chain Home. Furthermore, it could not accurately determine altitude, but it was a fully steerable and semi-mobile system. Freya was first successfully used on December 18, 1939 when two stations detected an approaching daytime raid on Wilhelmshaven by 22 RAF Vickers Wellington bombers at a range of 113 km and guided fighter planes toward them via radio. Only half of the Wellingtons returned to Britain undamaged, but the German fighters only reached the bomber after they had made their bombing run on ships in harbor. The performance of Freya left the "Luftwaffe" so impressed that by the Spring of 1940, eleven "Freya" stations were installed to guard Germany's western border. After the invasion of France in 1940, additional "Freya" stations were built along the Atlantic coast.