Editing Chain Home (section)

===First attempts, halting follow-up===
When jamming was first attempted by the Germans it was in a much more clever fashion than had been anticipated. The observation that the transmissions of the individual stations were spread out in time, in order to avoid mutual interference, was exploited.<ref name=war>{{cite web|url=http://www.radarworld.org/radarwar.pdf |title=The Radar War by Gerhard Hepcke Translated into English by Hannah Liebmann page 8-9 |access-date=10 February 2013}}</ref> A system was designed to send back spurious broadband pulses on a chosen CH station's time slot. The CH operator could avoid this signal simply by changing their time slot slightly, so the jamming was not received. This caused the station's signals to start overlapping another's time slot, so that station would attempt the same cure, affecting another station in the network, and so forth.

A series of such jammers were set up in France starting in July 1940, and soon concentrated into a single station in Calais that affected CH for some time. However, the timing of these attempts was extremely ill-considered. The British quickly developed operational methods to counteract this jamming, and these had effectively eliminated the effect of the jamming by the opening of the [[Battle of Britain]] on 10 July. The Germans were well on their way to develop more sophisticated jamming systems, but these were not ready for operation until September. This meant that the CH system was able to operate unmolested throughout the Battle, and led to its well-publicized successes.<ref name=war/>

By the opening of the Battle in July the German ''Luftwaffe'' operational units were well aware of CH, and had been informed by the DVL that they could not expect to remain undetected, even in clouds. In spite of these warnings, the ''Luftwaffe'' did little to address this and treated the entire topic with some level of disdain. Their own radars were superior to CH in many ways, but had proven to be only marginally useful. During the [[Battle of the Heligoland Bight (1939)|Air Battle of the Heligoland Bight]] in 1939, a German [[Freya radar]] detected the raid while it was still an hour away from its target, yet had no way to report this to any of the fighter units that could intercept it. Getting the information from the radar to the pilots in a useful form appeared to be a difficult problem, and the Germans believed the British would have the same difficulty and thus radar would have little real effect.

Some desultory effort was put into attacking the CH stations, especially during the opening stages of the Battle. British engineers were able to quickly return these units to service, or in some cases simply pretend to do so in order to fool the Germans into thinking the attacks failed. As the pattern of these attacks became clear, the RAF began to counter them with increasing effectiveness. The [[Junkers Ju 87]] [[dive bomber]]s were subjected to catastrophic losses and had to be withdrawn from battle. The Germans gave up trying to attack CH directly on any reasonable scale.<ref name=war/>

Thus, CH was allowed to operate throughout the Battle largely unhindered. Although communications were indeed a serious problem, it was precisely this problem that the Dowding system had been set up to address, at great expense. The result was that every British fighter was roughly twice or perhaps more as effective than its German counterpart. Some raids were met with 100% of the fighters dispatched successfully engaging their targets, while German aircraft returned home over half the time never having seen the enemy. It is for this reason that Churchill credits Chain Home with winning the Battle.