The systems they did use were very accurate for their time (as was the later British Oboe), despite the distances (and most of Britain is closer to occupied Eur

The systems they did use were very accurate for their time (as was the later British Oboe), despite the distances (and most of Britain is closer to occupied Europe than Eastern Germany is to Britain), so would not a spread-spectrum version be capable of similar accuracy, if the additional complications of implementation could be overcome? (and I am sure Germany's engineers were capable so doing.) I think the countermeasures for Knickebein were deployed before the Coventry raid, but the frequency being used was not detected (by sending up 'sniffer' airplanes) that night. According to Wikipedia, the interfering with Y-Gerät was mostly done at power levels too low to produce the 'ring-around', which was good enough to spoil the accuracy while not giving the game away, and leading the German engineers and technicians on a time-consuming and fruitless search for technical problems.