Cursitor Doom snipped-for-privacy@notformail.com wrote:[...] "passive
>>bistatic radar" > For example: >
> >>formatting link>>cpage/20171219/Session%201.0.pdf > > > John >
> >>
> >> For a long time, too. IIRC the first successful radar experiment used
> >> the reflection from a BBC transmitter.
> Radar and code-breaking really saved Britain's bacon in WW2. Plus a
> > bit of assistance from the old colonies. :->
> >
>
> Yeah, Auntie was useful for something back then.
The BBC transmitter was only used for the initial experiments to show that radio detection of aircraft was possible - after that, Chain Home stations each had their own transmitter which 'floodlit' the search area with pulses of RF. Navy transmitting valves were used st first but soon special types were developed to cope with high pulsed power. They were time-jittered to avoid mutual interference but all basically locked to the 50 c/s mains.
The Germans were experimenting with radar in the VHF region and thought we would be doing the same. When they sent two airships on a radio intelligence-gathering mission, up and down the North Sea coast just out of visual comtact, they concluded that the HF signals were just interference (becuase they were mains-locked) and we had no radar capabilities.
In fact we had been watching them the whole time with our radar. At one point they radioed their position and got it wrong - our radar operators were SO tempted to tell them!