Radio Broadcast (Nov. 1925-Apr 1926)

238 RADIO BROADCAST ADVERTISER To increase the effi' ciency of a receiver employing Resist' ance'Coupled Amplification, and to get the full measure of tone purity and faithfulness of reproduction, for which this method of amplification is noted, use Clear' tron Hi-Constron Tubes — Type 101A. IRON-CLAD GUARANTEE C-T 201 A C-T 199 Standard Base C-T 199 Small Base CTX 112 Power Tube $6.50 All Types Equipped With Genuine Bakelite Bases At All Reliable Dealers it Write for FREE six-page folder giving valuable information regarding radio tubes Cleartron Vacuum Tube Company Executive Offices 28 West 44th Street New York City factories West New York, N. J., U. S. A. Birmingham, England For Better. Reception Is Your Set How to Prevent Your Receiver Causing Interference and Thus Spoiling Your Neighbor's Reception CT^HERE are still many single-circuit bloopers in use, although the general trend in design, as far as commercially made receivers are concerned, seems to he toward receivers which are almost incapable of causing interference, however carelessly handled. The excellent instructions appearing helow have been specially prepared by the Radio Branch of the Department of Marine and Fisheries of the Dominion of Canada, for circular Ration among all Canadian broadcast listeners. On the back of all Canadian receiving licenses is the following note. " When using a receiver of the regenerative type for the reception of radio telephone programs, please avoid increasing regeneration to the point at which the receiver begins to oscillate, otherwise you will cause interference with neighboring receiving equipments. Are you doing your best to observe this?" The point is that many owners of receiving sets capable of radiating squeals, cause such interference purely from inadequate knowledge of the handling of their sets, and it was for their benefit that this circular was printed. These instructions should help many readers of Radio Broadcast who are looking for clear directions on how properly to use their regenerative sets. — The Editor. HOW MUCH INTERFERENCE A RECEIVER CAN CAUSE A RECENT survey of radio broadcast reception conditions in the more populated centers of the Dominion of Canada indicates that approximately fifty per cent, of the "preventable interference" which prevails, is caused through the incorrect operation o) regenerative receiving sets by the broadcast listeners themselves. The survey further indicates that most of the interference is due to a lack of knowledge of correct methods of adjusting a regenerative receiving set, and it is accordingly hoped that a material reduction in the same way may be effected if the broadcast listeners can be persuaded to cooperate in an endeavor to clear the air of regenerative whistles, and, with this end in view, the following instructions for operating this class of receiving set have been drafted. WHAT IS REGENERATION? Hp HE principle of regeneration, as used in radio receiving sets, is that a part of the output of the detector vacuum tube feeds back into its own input and thus greatly increases the volume of the signal. The electric waves reaching the receiving set from the transmitting station travel down the antenna wire through the primary coil in the set and so to earth down the ground wire. The weak electric current resulting from this influences the vacuum tube in such a way as to set it functioning. The resulting output from the plate circuit of this tube is fed back in such a manner as to set up a "field," or "influence," in the part of the circuit connected to the input (the grid) of the tube. This "field" induces in the input circuit a current of electricity of the same frequency as that of the received electric waves. The energy, therefore, which comes down the antenna wire is automatically strengthened by an impulse from the output of the detector lube. ■fa Tested and approved by Radio BROADCAST -^r