Nyorai kupfuurira kweiyi ndima - RDF yokutanga yakabudirira yeRoyal Navy yaiva "Type 79Y Surface Warning", yakaedzwa mugungwa mukuvamba kwa1938. John D. S. Rawlinson akanga ari mutungamiriri webasa racho. Iyi 43-MHz (7-m), 70-kW yakagadzirirwa yakashandiswa kutumira uye kugamuchira antennas uye yaiva nehuwandu hwemakiromita 30 kusvika ku50, zvichienderana nekukwirira kweantenna. Pakazosvika 1940, iyi yakava "Type 281", yakawedzerwa mukuwanda kusvika ku85 MHz (3.5 m) uye simba kusvika pakati pe350 ne1,000 kW, zvichienderana nehupamhi hwepuls. Neantenna dzinodzora, yaishandiswawo nokuda kweGun Control. Iyi yakatanga kushandiswa muhondo muna March 1941
nokubudirira kukuru. "Type 281B" yakashandisa imwechete inotumira uye inogamuchira antenna. "Type 281", kubatanidza shanduro yeB, ndiyo yakanga yakanyatsoedzwa muhondo metric system yeRoyal Navy muhondo yose.