British and American fighter-direction radio systems

The British fighter-direction office used a four-channel wireless arrangement that could separate radar reports from other fleet sightings before passing useful information to the combat air patrol. American practice placed heavier demands on radio because Japanese direction finding made surprise and transmission discipline important. VHF imposed a line-of-sight limit, while switching to medium frequency after detecting a raid could add fighter-control traffic to already busy channels. HMS Victorious's Pacific service as USS Robin shows that both navies possessed working fighter-direction systems before the Big Blue Blanket reached its mature late-war form. Communications architecture was integral to air defence alongside radar.