 Scientific intelligence gave about six weeks' warning that these raids would employ "X-Gerät" with a new supersonic modulation frequency.80 Wing was able to add supersonic modulation to its jammers, but was briefed not to employ this countermeasure until listening stations had confirmed that the "Luftwaffe" was indeed using the new technique.Unfortunately, the designers of the listening receivers had overlooked the fact that supersonic reception involves a wider bandwidth than normal in the high frequency circuits of the receivers.