Pieter
Regarding the TR 1133 being introduced in May 1940, the RAF / MoD stated the following in their Battle Of Britain 70th Anniversary publication:-
"Ground-to-air and air-to-air communications were facilitated by another technological advance - very high frequency (VHF) radio. In 1939 Fighter Command aircraft were still equipped with TR 9D high frequency (HF) radios. An operational trial undertaken with the new TR 1133 VHF radio by No 11 Group in October 1939 showed it to be "infinitely superior to the TR 9D (HF) from an operational point of view". "
"Despite its improved performance, delays in production forced Fighter Command to withdraw the TR 1133 from service in May 1940. Although the new set was reintroduced from August 1940, the limited number of VHF radios available nevertheless meant that the majority of squadrons would be forced to continue with the earlier TR 9D HF radio for the remainder of the battle."
Published in association with Royal Air Force Media and
Communications, Headquarters Air Command
www.raf.mod.uk
Mark