Foundation for German communication and related technologies

[Empiricist]

Hello

It's an interesting set of the subjects and links. I would like to know who was a pioneer of quartz-crystal radio for military aircraft -- the Germans or the Americans? No doubt the Americans were the leaders of quartz-crystal filters, resonators and generators at the Allied side. They used Brazilian natuarl quartz which is the best in natural category up to this time. Do you know who manufactured aircraft radio with quartz-controlled frequency as the first country in the world?

Regards

E.