On Mon, 15 Jun 2009 20:32:40 -0500, tom wrote:

stan wrote:

It was identifying the reflection of radio signals from a flying
aircraft that led to the development and use of radar.
Radar was major factor in the successful defence of Britain (Britain
1940) against German bombing (The Blitz) early in WWII (1939-1945).
Although it was initially very crude, (It was called Radio-location or
RDF, Radio Direction Finding) at the time.
Unfortunately the first war time US use of radar was misinterpreted
when the Japanese attacked Pearl Harbour in Dec 1941!

Actually it was blocking of a radio transmission by ships passing on a
river that led to the development of radar.

tom
K0TAR

RF blocking was used by both sides as a "burglar alarm" to detect
naval vessels passing through narrow straights. Germany tried to get
such a system working across the Straits of Gibraltar, but were foiled
by Spain's failure to cooperate.

Radar was officially "invented" in 1935 when Watson-Watt was asked by
the air ministry to calculate the possibility of using RF as a "death
ray" to cook an airplane pilot in flight. Some calculations were
performed which quickly determined that it was impossible. However,
he suggested that a similar system could be used to detect the
airplane by combining the range finding of ionospheric layers
techniques and the direction finding techniques used to detect
thunderstorms. At the time, there were also proposals for aircraft
detection using infrared and sound detection. Not wanting to lose
their funding, it was agreed that RF reflection was a good idea and
that research should continue on this different path.


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Jeff Liebermann
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