[Pieter H]

Mark, Andy,

Thanks for the additional info.
I think we're all saying the same thing, namely that the TR9D was the main radio set for RAF fighters in the May 1940 period (and well beyond). All I said was that formally the TR1133 became available around that period, without any statements about its possible widespread use. Your info about the rate of adoption are very interesting.

In fact, looking back, it is rather shocking to see with what quality of radio equipment the RAF aircraft were equiped. The so-called linear or straight receivers are known to have very poor sensitivity (=range) and were difficult to keep tuned (=stable). Almost all German radios of the period were already super-heterodyne, with much higher sensitivity, tunability and stability. And companies like Philips used the same concept in commercial radio receivers. The TR1133, although much improved, was still a linear receiver. That makes it all the more interesting to see that even under the pressure of war it took all of 1940 to get the TR1133 into production. And only the next model, the Marconi T1115/R1116 was finally based on super-heterodyne principles. Although some sources say this one came available June 1940, I suspect operational roll out of this one was not before 1941.

Regards, Pieter