Radio Broadcast (Nov. 1925-Apr 1926)

230 RADIO BROADCAST ADVERTISER Helps to Land Everything You Catch The "Electrad" Lead-in meets that high quality standard set by all "Electrad's" products. There is a difference. The convenient lead-in. Now you need not scar or mar your walls or sash with unsightly holes or ugly porcelain tubes. This flat, highly insulated and waterproofed lead-in fits under locked windows and doors. The windows may be closed tightly — there need be no loss of heat in the room. Pliable, it bends into any shape — meeting your every need. Price 40c Other Guaranteed Electrad Radio Products which simplify construction, facilitate installation and improve reception of radio sets — Variohms, Lamp Socket Antenna, Certified Grid Leaks, Resistance Coupled Amplifier Kits and many others. At your dealer's, if he can't supply, write us. ELECTRAD, Inc. 428 Broadway New York City "ELECTRAD" AUDIOHM A necessary tone and quality controlling device. Placed across secondary of first audio transformer it eliminates distortion and transformer noises. Requires no drilling, soldering or tools to attach. Fits any transformer. $1.50 each. "ELECTRAD" LIGHTNING ARRESTER Price 50c. Indoor type. Approved by Underwriters. Should fire occur from lightning you will have insurance difficulties unless you have an approved arrester. ELECTRAD The Six Point Pressure Condenser The "Electrad" Certified Fixed Mica Condenser is a revelation in accuracy and design. Ingenious, rigid binding and firm riveting fastens parts securely at Six different points insuring positive electrical contact. Impervious to temperature and climatic variations. Exerts even pressure upon the largest possible surface — can't work loose. Binding strap and soldering lug in one piece. Accuracy and quietness assured always. Value guaranteed to remain within 10% of calibration. Standard capacities, 3 types. Licensed under Pat. No. 1,181,623 May 2, 1916 and applications pending. Price 30c to 75c in sealed dust and moisture proof packages. type of tubes, it will be necessary to change the radio-frequency transformers also, if equally efficient results are to be obtained. This is made necessary by the fact that the characteristics of the tubes vary according to their internal construction. In the uv-199 tube, the elements are very close together, making it possible and advantageous to use more wire on the primary of the transformer. The tendency for a vacuum tube having a tuned input circuit to oscillate, is proportional to the inductive load or the number of turns on the primary of the transformer in the plate circuit. If the tubes were replaced with the c-301-A or uv-201-A type, the circuit would become unstable and oscillate readily, due to the difference in construction of the elements of the latter type of tube. Fewer turns of wire should be used on the primary of the transformers. The curve of the transformer will fall off at one end of the scale and result in poor amplification of either the high or low waves, if the proper type of tube is not used. This is due to the capacity of the input circuit of the tube, which varies in different tubes. As this is shunted across the secondary winding, it has sufficient tuning effect on that winding to shift the area of maximum amplification from the desired band. When the tube characteristics are matched up with the correct amount of wire on the primary of the transformer, then the circuit will cover the whole wave band evenly, with good amplification. In some types the core of the transformer is filled with finely powdered iron or iron laminations. The use of iron in the core broadens tuning so that the transformer may be used over the entire wave band, without the need of a variable condenser for tuning. When Writing to the Grid — A TYPEWRITTEN letter, written on one side of the paper only, is to be preferred,as it aids in the quick formation of a satisfactory reply. Don't fail to send a stamped addressed envelope with your inquiry. Don't send a second inquiry about the first. Don't include questions on subscription orders or inquiries for other departments of Doubleday, Page & Company. In asking questions give us all the information that will aid in advising you. If the question relates to apparatus described in Radio Broadcast, give the issue, page number, and figure number of the circuit diagram, etc. Be explicit yet brief. GRID INQUIRY BLANK Editor, The Grid Radio Broadcast Garden City, T^eiy Tori^ Dear Sir, Please give me the fullest information on the attached questions. I enclose a stamped envelope. I I I am a subscriber to Radio Broadcast and therefore will receive this information free of charge. I I I am not a subscriber and enclose $1 to cover cost of answers. Name Address G. D. •jt Tested and anmoved by Radio BROADCAST