My browser leads me to an error page. 

Could you quote the article title, please?

 

H.

 

Some photos from http://midia.largadoemguarapari.com.br/01antesdainvenodoradar/index.htm

 

http://midia.largadoemguarapari.com.br/01antesdainvenodoradar/03.jpg" />

 

http://midia.largadoemguarapari.com.br/01antesdainvenodoradar/11.jpg" />

 

http://midia.largadoemguarapari.com.br/01antesdainvenodoradar/16.jpg" />

 

http://midia.largadoemguarapari.com.br/01antesdainvenodoradar/12.jpg" />

http://midia.largadoemguarapari.com.br/01antesdainvenodoradar/02.jpg" />

Thank you very much! Starting in WW I, first the British, and then the Germans established "ear trumpet" air raid warning systems. They knew the speed of sound in air, and they had a rough idea of how sensitive Human hearing was.

 

Using a clever system of testing the British were able to actually devise a rough crude range gauge for when a Human being could expect to hear motor noises aloft, so they could estimate rough ttime interval based on heard Doppler. It did not of course give accurate range to engage with aimed weapons, but it did give some usable warning so that searchlight cues and radio telephone ground direction could point aircraft into successful intercept bearings even at night. 

 

What the British did, the Germans duplicated.

 

Those, who did not or could not duplicate the ear trumpet method, had to use binoculars and local ground observers for their warning networks.

 

Odd thing is that people seem to forget that we still use this technology as updated with modern tech. It doesn't occur to most people that we still use atmospheric acoustic detection as part of our warning systems. We don't throw anything this cheap that works this well against most countermeasures away-ever.  

 

H.