Variometer.jpg
Summary
Description Variometer.jpg |
English:
A variometer, an adjustable air core
inductor
used in radio equipment, from a 1920 book on radio. It was widely used in radio receivers during the 1910s and 20s. Today it is mostly used in transmitter
antenna tuners
and matching sections for low frequency antennas, to match the transmission line to the antenna.
It consists of two coils of wire with the same number of turns, connected in series. The inner coil is mounted on a vertical shaft that allows its axis to be turned with respect to the outer coil. When the inner coil's axis is parallel to the outer coil and their magnetic fields are in the same direction, their magnetic fields add, so their inductance is maximum. When the inner coil is turned so that it's axis is at an angle to the other, the mutual inductance between them is smaller so the total inductance is less. When the inner coil is turned 180° so its axis is parallel with the outer but their magnetic fields are in opposite directions, they subtract so the total field, and thus the total inductance, is very small. Thus the inductance can be continuously adjusted over a wide range. |
Date | |
Source | Downloaded April 30, 2013 from Elmer Eustace Bucher (1920) The Wireless Experimenter's Manual , Wireless Press, Inc., New York, p. 189, fig. 150a on Google Books |
Author | Unknown author Unknown author |
Licensing
Public domain Public domain false false |
This media file is in the
public domain
in the
United States
. This applies to U.S. works where the copyright has expired, often because its first
publication
occurred prior to January 1, 1929, and if not then due to lack of notice or renewal. See
this page
for further explanation.
|
||
This image might not be in the public domain outside of the United States; this especially applies in the countries and areas that do not apply the
rule of the shorter term
for US works, such as Canada, Mainland China (not Hong Kong or Macao), Germany, Mexico, and Switzerland. The creator and year of publication are essential information and must be provided. See
Wikipedia:Public domain
and
Wikipedia:Copyrights
for more details.
|