QST/April 1916/Something for Everyone

< QST‎ | April 1916

This article appeared in the April 1916 issue of QST

A Device Used by the Marconi Company

 While visiting a friend learned the following simple method of increasing radia-

Chokes from the April 1916 QST.png

tion, reducing the safety gap sparking, and also preventing the puncturing of transformer secondaries: For a quarter to one kilowatt sets, wind two coils of No. 4 to 12 copper wire around a tube one inch in diameter, consisting of about ten turns each. Place these air choke coils on each terminal of the transformer secondary and connect to the high frequency condenser so that each is in series with one side of the charging circuit. This air choke prevents the charged condenser from backing its current into the transformer, provided that the choking effect is greater in the coils than in the closed oscillatory circuit. The coils should he air spaced and about ¾ of an inch in turn.

 To prove there is no backward discharge at the transformer, leave a small gap at the terminals of the transformer secondary and an arc will be formed instead of a crashing spark. This simple device by directing all the energy to the close circuit, increases radiation but does not effect the wave length. For a 2½ Kw. set, the writer uses two coils of No. 4 aluminum wire consisting of ten turns, two inches in diameter, and spaced one inch.

This work is in the public domain in the United States because it was published before January 1, 1926. It may be copyrighted outside the U.S. (see Help:Public domain).