 This major embarrassment was due largely to supremely effective jamming on the part of the Germans, who managed to render the CH and CHL radars covering the coast entirely ineffective without the operators even noticing.To address this, the RAF began development of the AMES Type 11, a truck-mounted CHL system operating at 500–600 MHz.This frequency was chosen to match that of German anti-aircraft radars, in the hopes that the signals would be more difficult to notice, and that jamming would have negative effects on the German's own radars.