content: Because if it exists it can't be kept secret. These are active radiation emitters. Sigtel has special aircraft which do nothing but look for signals in a massive spectrum. The only way radar can be improved is to use it. The new technique and spectrum would be identified very quickly. So there is no advantage in keeping it secret. In fact, it's actually a disadvantage to keep it secret because it means you can't use it. Therefore, there is propaganda advantage in announcing it's use.