Radio Digest (Oct 1923-July 1924)

RADIO DIGES T— Illustrated October 20, 1923 RE-RADIATION PROBLEM tinned from pace 7") given from throe to ten sots in an immediate locality, all receiving a program from one particular station, it is a foregone conclusion si will be tuned just a little differently from all the others with the result that the entire hand of audible frequencies from this station is blanketed, and any super-sensitive in that neighborhood is completely and effectually barred by interference from receiving: this program. Furthermore, it is entirely too much to expect that these transmitting receiving set operators will all stick to the program from one station and send out a band of interference on that wave length alone. They will have different tastes, and divide their attention about equally between all stations within range which are broadcasting, thus blanketing all of them. The example of the effect upon a supersensitive receiving set is cited, because it foreshadows the dire result imminent unless the growth of this evil is checked and finally eliminated. The super-sensitive set will pick up an amount of interference today which the average set would not pick up for a year or two to come when the number of sets in operation is double or treble, and providing, of course, that retransmitting sets are then used in their present proportion. Concentration on One Station "?Vith the average set in operation today, a lot of dissatisfaction with the quality of transmission of programs from distant stations is directly due to distortion caused by interfering waves from neighboring re-transmitting receiving sets, and finally a lot of more or less momentary periods of inaudibility of programs from distant stations, which is generally attributed to the phenomenon of fading, is in reality caused by pronounced periods of interference as explained above, when a number of operators are concentrating on that particular broadcast. The idea is not supported by proof, and the suggestion would no doubt cause general surprise that possibly certain stations locally noted for pronounced fading may in reality be so near the middle ol the tuning range, and so popular, that they draw this concentrated fire of Radio receiver interference. Trouble due to fading from natural causes is serious enough at certain times of the day without its being increased by artificial means. The above indictment is written around the regenerative detector single tube or triple tube sets where two stages of audio RADIOTELEPHOTO FROM JAPAN This picture, which shows the ruins of the U. S. Embassy building at Tokio after the earthquake, reached Los Angeles by Radio from Honolulu, where the original arrived by steamer. It was then relayed by Radio from Los Angeles to New York * © P. & A. frequency amplification are employed, because they are by far the most numerous offenders, but retransmission is not confined to them entirely. Freely oscillating Radio frequency amplifiers, ahead of anytype of detector with or without audio frequency amplifiers, create disturbances of various degree, according to the size of the antenna or loop system used in conjunction with them. All of the above statements which are made positively are supported by fact. The questions raised are of extreme importance to all Radio enthusiasts and amateurs, and if you, for one, are not satisfied that they are true, then investigate until you are convinced, and govern yourself accordingly. It's Up to Fans Are we individually going to allow the Radio engineer or manufacturer of equipment to solve this problem for us? They can only take care of new installation and new equipment. We must take care of our own existing equipment, and call an immediate halt on this woeful impediment THE Tf.AOe MARK AUDIOPHONE RIG U. 3. MT. OFFICE Quality of reproduction such as only the original itself can equal. Speech that is so distinct that the voice heard is the actual voice of the speaker. Music that requires no tolerant imagination to be recognized as music of the finest type. Bristol's Single Stage Power Amplifier gives additional VOLUME with any two stage amplifier. No separate batteries required. It provides the additional volume necessary to bring in very distant stations on the loud speaker. Write for bulletin and address of the nearest dealer handling our instruments THE BRISTOL COMPANY WATERBURY, CONN. Boston New York Philadelphia Pittsburgh Detroit Chicago St. Louis San Francisco to progress. We must do it now for mutual protection, and not wait until the KELLOGG CONDENSER \fery true! rotor plates bolted at ends— no "shorts" Now when it comes to condensers real radio bugs can appreciate this: heavy aluminum plates securely bolted across to assure uniform air space between the plates; a five-plate vernier gives "clean cut" tuning; heavy Bakelite end pieces make a rigid mounting; no "shorts" because it is impossible for plates to touch. Here is a condenser that will be true to you. The price, which is always standard, is $8.75 for 43 plate and vernier but that does not prevent the real radio rascal from having it Wrapped up to take home — this very night. Another thing, this price includes dial and vernier knob. Use-Is the Test KELLOGC SWITCHBOARD 6 SUPPLY COMPANY CHICAGO whole structure of Radio business topples over from sheer lack of a sound foundation or defective first story. This citing of conditions, causes and effects, would not be complete without offering solutions to problems, and remedies for abnormalities. Your attention is imited to the opinions of various reputable Radio engineers and designers that the use of "neutrodyne" or compensating capacities across the elements of Radio frequency amplifier and regenerative detector tubes will prevent undesirable "feedback" or regeneration, and resultant retransmission. A single stage of transformer coupled Radio frequency amplification ahead of the ordinary regenerative detector will damp out to a great extent the retransmission of interference, and at the same time increase sensitivity to a marked degree. ."©RMICA^ Almhiui}l\iw]ir(m4nB31km Product . 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