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Loose Couplers

Also known as a "Receiving Transformer", loose couplers were used extensively in receivers built during the "teens". The coupler consists of two coils, a primary and a secondary. The primary coil is stationary and is usually provided with a slider for varying the inductance by single turns. The secondary coil slides in and out of the primary to vary the coupling, and is designed with several switch points in order to change its inductance.

Loose couplers were used as the primary tuning device in early receivers. The primary coil was attached to an antenna and ground (sometimes through a variable condenser.) The secondary was connected to a detector (typically a crystal detector in the early sets.. see detectors for more information.)


Simple crystal radio using loose coupler

By the early 20's the loose coupler had lost favor as a tuning element to variometers and variocouplers, 
with their advantage of smaller size and panel mounting. Below are some examples of loose couplers 
in my collection:


Chambers Loose Coupler


Murdock Loose Coupler

Arlington Receiving Transformer

Navy type Loose Coupler

Unidentified Loose Coupler
c.  1916

Adams Morgan #520

Clapp Eastham
Slide Coil Tuner

Unidentified Loose Coupler
c.  1916

Tel-Radion Loose Coupler
c.  1912

William B. Duck
Loose Coupler

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