 Mounting the receiver in the Heyford was not a trivial task ; the standard half @-@ wave dipole antenna needed to be about 3 @.@ 5 metres ( 11 ft ) long to detect wavelengths of 6 @.@ 7 m . The solution was eventually found by stringing a cable between the Heyford 's fixed landing gear struts . A series of dry cell batteries lining the aircraft floor powered the receiver , providing high voltage for the CRT through an ignition coil taken from a Ford . 
