 By 26 July 70 Blenheims were equipped with Mk . III and the RAE wrote an extensive report on the system . They too had concerns about what they called " partially reliable " systems and pointed out that a significant problem was due to the unreliable antenna connections and cabling . But they went further and stated that the self @-@ exciting concept would simply not work for a production system . These systems used transmitter circuitry as an oscillator to produce the operating frequency , but they had the disadvantage of taking some time to stabilize and then shut down again . Hanbury Brown agreed with this assessment , as did Edmund Cook @-@ Yarborough who had led work on the IIIB at Dundee . 
