GR tuning coil
Datecirca 1915
Inventory NumberRS0557
ClassificationTuning Coil
Subject
Maker
General Radio Company
1915-present
Maker
Clapp-Eastham Company
1906 - 1929
User
Cruft Laboratory, Harvard University
founded 1914
Cultural Region
Place of Origin
Place of Use
Dimensions12 x 12.5 x 10.5 cm (4 3/4 x 4 15/16 x 4 1/8 in.)
Material
DescriptionCoil encased in a cylindrical brass body with dark discoidal top panel. Large dial with 2 electrical connectors on top. The Dial has a scale 0-100 and it is turned with a long lever.
In Collection(s)
Signedon dial: GENERAL RADIO CO. / CAMBRIDGE, MA
Curatorial RemarksThe coil is described as as "Tuning coil, Clapp Eastham Co." but is signed General Radio. May have been manufactured by Clapp-Eastham around the time of the founding of General Radio.
FunctionThe frequency of transmission or reception of a radio circuit is inversely proportional to the square root of both its capacitance and inductance. Tuning coils are one of the methods used to alter a circuit's frequency, by altering the circuit's inductance.
In this particular case, the inductance of the coil (which would be part of the circuit) is changed by turning the lever, which makes one of the points of electric contact move to a different location on the coil wires, changing the effective size of the coil. Less wire and loops between the two electric contacts means a smaller inductance.
In this particular case, the inductance of the coil (which would be part of the circuit) is changed by turning the lever, which makes one of the points of electric contact move to a different location on the coil wires, changing the effective size of the coil. Less wire and loops between the two electric contacts means a smaller inductance.
ProvenanceFrom the Cruft Laboratory, Harvard University.
Historical AttributesCruft
Hearwell Radio Company
Date: ca. 1915-1930
Object number: RS0780
