Westinghouse_experimental_700_MHz_transmitter_1932.jpg
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Summary
| Description |
English:
An experimental 700 MHz
microwave
transmitter
on the roof of the
Westinghouse
office building in 1932, part of early research that resulted in
microwave relay
systems by the 1940s. The 16 inch waves radiated by the vertical dipole
(right)
are focused into a beam by the cylindrical parabolic reflector, which is received by another parabolic antenna a mile away. The microwaves were probably generated by a
Split-anode magnetron
, an obsolete vacuum tube oscillator that was one of the few sources of microwaves at that time.
|
| Date | |
| Source | Retrieved March 19, 2015 from Short Wave Craft magazine, Popular Book Co., New York, Vol. 2, No. 6, April 1932, p. 378 on http://www.americanradiohistory.com |
| Author | Unknown author |
|
Permission
( Reusing this file ) |
This 1932 issue of Short Wave Craft magazine would have the copyright renewed in 1960. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here . Search of the Renewals for Periodicals for 1959, 1960, and 1961 show no renewal entries for Short Wave Craft . Therefore the copyright was not renewed and it is in the public domain. |
Licensing
|
This work is in the
public domain
because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the
copyright was not renewed
. For further explanation, see
Commons:Hirtle chart
and
the copyright renewal logs
. Note that it may still be copyrighted in jurisdictions that do not apply the
rule of the shorter term
for US works (depending on the date of the author's death), such as Canada (70 years
p.m.a.
), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
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