Dynatron_signal_generator_1931.jpg
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Summary
| Description |
English:
A
vacuum tube
signal generator
from 1931, the Model 303 made by Wireless Egert Engineering, New York. 10x8x7¼ inches. It uses a
dynatron oscillator
circuit, an uncommon circuit that uses the
negative resistance
of an early
tetrode
tube caused by an effect called
secondary emission
. The dynatron circuit was used in precision oscillators from about 1930 to 1945 because of its frequency stability, which reportedly was compared with crystal oscillators. Plug in coils
(one shown at bottom)
allowed it to cover the 165, 80, 40, and 20 meter bands, from 1.8 to 15 MHz. The meter was used to keep the space charge in the tube constant.
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| Date | |
| Source | Retrieved October 27, 2015 from Radio News magazine, Radio Science Publications, Inc., New York, Vol. 8, No. 1, July 1931, p. 54 on http://www.americanradiohistory.com |
| Author | Unknown author |
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Permission
( Reusing this file ) |
This 1931 issue of Radio News magazine would have the copyright renewed in 1959. 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 1958, 1959, and 1960 show no renewal entries for Radio News . 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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