NAB reports (Mar-Dec 1933)

tion you get in between synchronized stations. At times the reproduction is very distorted so that it is quite impos¬ sible to listen to a program without real discomfort. At other times it will improve and be good. A good deal of work has been done in studying what constitutes permissible value, and the ratio is four to one. Four times, the strength on the other side gives quite good reception. Careful tests made by skilled observers can get no distortion on such condi¬ tions but it is very probable that three to one is satisfactory in most eases. If the carrier frequencies of two stations differ slightly you get added effects, requiring a ratio of something like ten to one. “To synchronize stations in one region there cannot be any appreciable frequency difference in transmitting the same program. There is another great advantage to be obtained by the use of a linear detector, since that type of a receiver gives an independent carrier ratio on a detector — that is, unless you have automatic gain control. Automatic gain control af¬ fects this factor, sometimes. “In the early days of synchronization, it was very difficult to keep within a small fraction of a cycle and maintain con¬ trol of carrier frequencies over entirely indefinite periods. Two such systems are available and make it possible to hold in synchronism two stations which are a few miles apart. You may not, of course, have too much time delay between programs for the requirements are very rigid. A plan for synchronization is available and the problem is more one that is up to the industry to vote for commercial application than it is to the engineering division to further improve the technical aspects of the equipment, for they are well ahead of the game. “There has recently been discovered a synchronizing system whereby it is possible to limit the distortion between stations ten miles apart. That, I think is the present picture of the possibility of synchronization.” MR. HARMON : “As some of you know, the Westinghouse station has been operated since 1926 under certain circum¬ stances. The wire line systems used have a carrier frequency band of 27 k.e. We have very little difficulty in synchroniza¬ tion of these two stations and they are still being operated today.” MR. NELSON : “With regards to Mr. Aiken’s statements, I feel they may be lost in the large amount of very inter¬ esting discussions of the very interesting difficulties being en¬ countered in synchronization. There have been a large num¬ ber of organizations devoted to this particular problem and I hope it can be safely said that from a technical standpoint that what you need today is a synchronized job which can be made available and perfected to an extent for practical operation. The matter now becomes a problem of the indus¬ try to appreciate new instruments which would make it pos¬ sible for them to improve the amount of service they are giv¬ ing the country at large. There are two factors necessary for progress in this line. One problem that has to be worked out nonteehnically is that of assuring cooperation between the various stations involved on a given channel, for example, be¬ cause that is the soundest way to proceed. Certainly we can¬ not say that the time has arrived to give up the clear chan¬ nels for such purposes and the value of application where such stations must exist lies on the regional channels. Under the new deal, there ought to be no difficulty in securing syn¬ chronization along this line. The outlook for synchronization is very bright; the treatment is up to you.” MR. LOYET : “I would like to say a little bit on the synchronization plan. I would like to point out that we offered to do that when first synchronization was introduced and suggested with both diagrams and paper talk that you could discriminate against one station and another by means of ground loop or antenna and I don’t believe we ever re¬ ceived a letter from a single listener that they had improved a station. If he can get results, he isn’t going to put up a complicated lay-out to receive one station. He will be satis¬ fied with the rest of the stations he can get regardless of signals. So anybody offering use of the idea of changing receiver design in order to pick up stations is going to be laboring under difficulties.” CHAIRMAN: “Any further discussion?” MR, FOSS: “May I ask Dr. Jolliffe regarding this syn¬ chronization plan — if he has any comments to make as far as the Commission is concerned?” DR. JOLLIFFE: “I was hoping I was going to get out of this discussion. I wish to point out expressly what Mr. Nelson says. We are interested in bringing about a study of the systems of broadcasting. There are many individual cases which from an economy standpoint or listener’s standpoint might give better attention to the question without hurting too many people. These few people involve considerable pub¬ lic interest. “Consequently in applying this in allocation, we must watch New York and immediate service areas of stations of clear channel class. However, in the local channel class, there is the possibility of considerable improvement in the locations that were originally made and there are some bad spots. Many bad spots could be improved by improving the fre¬ quency control. A large amount of improvement was noted with respect to reducing the frequency control from 500 to 50 cycles. We now have further increases in the service area of some of these stations which must come about from their own efforts in further frequency control. If they can get frequency control they have improved their service area or added listeners to their improved service. In other words, in the regional or local class, synchronized experiments expand a station. On the dear channel synchronization, there is apt to be more than one station on, which will decrease the quality of that channel whether it be to a small number of people or to a large number of people. Synchronization comes about in the class of channel you are working on.” CHAIRMAN : “I think we will have to call a halt in the discussion of that. The next business is that of the North American Conference and Mr. J. W. Baldwin of the N.A.B. is going to tell us something about that.” NORTH AMERICAN CONFERENCE By JAMES W. BALDWIN MR. BALDWIN : “Gentlemen, there could not be a more opportune time than this to talk to a group of engineers who are seriously interested in the art of broadcasting. The duties of the station executives, embracing as they do, mat¬ ters concerning commercial accounts, program construction and public policy should never be minimized but the fact re¬ mains that radio engineers must provide the vehicle without which all other labor goes for naught. “Never in the history of American broadcasting have you gentlemen of the Engineering fraternity had so great a re¬ sponsibility for the future of American broadcasting as now. This fact has been forcefully emphasized at the meetings, which have been held in Washington, since late in February, preparatory to the Central and North American Radio Con¬ ference, which will convene in Mexico City on July 10th. “By reason of a strict injunction of secrecy imposed upon the participants by the Department of State, we have been unable to inform the membership concerning matters of great¬ est importance to every broadcaster in the United States. Our protests against the injunction of secrecy were unavail¬ ing. ‘•'At the outset we filed a statement of our position, declar¬ ing in substance, for a widening of the broadcast band so as to include 10 carrier frequencies below 550 k.c. and opposing the use of any frequencies above 1500 kc as compensation for frequencies in the band 550 k.e.— 1500 k.e. that may be given to other countries. Our statement was supported by all the technical data that could be made ready in the time allowed. “One of our most serious handicaps has been the lack of sufficient technical data to mould public policies. We know that the whole weight of scientific research favors the use of low frequencies for broadcasting. But it is nevertheless in¬ cumbent upon us to build a record of quantitative data that will be overwhelming in the minds of those whose responsi¬ bility it is to shape government policies. “Let me say to you at this point that the N.A.B. has at its headquarters a radio engineer of whom the membershiij can justly be proud. I know that I reflect the opinion of many when I say that J. C. McNary will travel far in the . Page ICS .