Supposing that transmitters of absolute constancy are concerned, the following band-widths may be accepted: Broadcasting (music), facsimile and telephotograph transmitters, total band-width, 20,000 periods per second. Multiple telephony, each conversation, 8,000. International telephony (one conversation) and black and white facsimile: 10,000. Telegraphy at 300 words a minute: 2,000. In the last case the method of counting is as follows: 300 words a minute represent 125 dots a second. The rectangular form of the modulation may be arranged in the form of Fourrier series: A frequency of 125 periods p/sec. It is supposed here that the higher harmonics have very small influence on the clearness of signals. It is recommended that, for keying, a pass filter of a limit of passage of less than 1,000 periods p/sec. should be used and placed between the relay and the transmitter, properly so-called; this, in order to avoid the "clicks" of the key. 75 DUTCH EAST INDIAN PROPOSAL CONCERNING TOPIC 8 OF THE PROGRAM PROTECTION OF LONG-DISTANCE SERVICES ON SHORT WAVES The development of short waves during recent years has shown that these waves play a very important part in long-distance work (more than 5,000 km). Long-distance traffic on short waves has greatly developed and has become of the first importance. In the near future an increase of this traffic is very probable and serious overcrowding of radio stations in the 6,000 to 23,000 kc/s band will be inevitable. The consequences of such overcrowding are at once intolerable interferences, which may cause serious disturbance to international services. The International Bureau at Berne has not the power to decide this matter finally and can only give notification of information received from the administrations. At the present moment, the situation is such that it seems difficult to find a solution in international conflicts. Means should be found to avoid these conflicts in the future and above all to protect services of a primary nature against disturbance and interference from less important services. The only decisive method will be to reserve for primary services a certain wave-band and to fix the frequencies of the various posts sufficiently far apart that they may not disturb one another, while two posts working on the same or about the same wave-length will not be tolerated. In the United States proposal the following rules are suggested for this case: (a) Frequencies from 6,000 to 9,000 kc/s (waves of 50 to 33 meters) are recognized as especially suitable for international work. These waves may be duplicated during the day, during periods in which the transmitting station is in full daylight. with the nearest sunrise or sunset wall at least one hour away. (b) Frequencies between 9,000 and 23,000 kc/s (wave-lengths 33 to 13 meters) must not in general be duplicated, save where it has been clearly shown that such duplication is possible without interference. Posts will be divided into three classes: 1. Primary-without any restriction. 2. Secondary-with the restriction that interference with the international work of a primary station must be avoided. 3. Tertiary-with the restriction that interference with primary and secondary stations must be avoided. The first class will be limited to long-distance services (more than 5,000 kilometers). With these rules long-distance services may for the moment be sufficiently protected. Unfortunately the division given in the Washington 1927 Regulations shows that the great importance of frequencies between 6,000 and 23,000 kc/s (wave-lengths 50 to 13 meters) for long-distance services has not yet been sufficiently considered. From a study of Fig. 1 it may be seen that for fixed services only a percentage of 59 per cent of the total is specially available for this service. Calculating on the basis that the total communication-band of a station can not be more than 0.1 per cent of the frequency, the number of posts possible in the bands, it will be found that in all 1,315 stations are available: 741 for the fixed service. 273 for the mobile service. 147 for the mobile and fixed service. 76 for the broadcasting. 68 for amateurs. Mixed bands are less desirable for long-distance services, owing to the greater possibility of interference in this band by mobile stations whose frequencies are less stable and which are often difficult to reach when they cause interference (ships, airplanes, mobile military stations). A change in this division will be very desirable shortly. As a preliminary suggestion in this respect, without in any way claiming that it should be decisive, the Dutch East Indies Administration recommends that (a) The mixed bands in the 6,000 to 23,000 series should be suppressed, and that these bands should be added to the fixed services. (b) Certain bands in the mobile services should be changed and certain of them should be suppressed; thus 8,550 8,900 (mixed band) to be given to fixed services. 12,825-13,350 (mixed band) to be added to fixed services. 17,100-17,750 (mixed band) to be added to fixed services. 22,300-23,000 (mixed band) to be given to fixed services. 21,550-22,300 (mobile services) to be added to fixed services. The result is given in Fig. 2. The advantages of this change would be: (a) Increase of frequencies for fixed services. (b) A rather more continuous and less complicated spectrum. The number of possible stations on the same basis of 0.1 per cent will be: 922 fixed stations. 239 mobile stations. 76 broadcasting stations. 68 amateur stations. There are also a certain number of other combinations possible. The Dutch East Indies Administration, although convinced that such changes are not within the competence of the C. C. I. Radio, thinks that the question is so important that 1. The assembly of the C. C. I. Radio should express a wish that this question may be placed on the program for the next international conference at Madrid in 1932. 2. This question should be submitted to suitable expert reporters. 76 DUTCH EAST INDIAN STATEMENT CONCERNING TOPIC 12 OF THE PROGRAM ALLOCATION OF WAVES TO AVIATION In the experience of the Royal Marine in the Netherland Colonies, waves above 335 kc/s (wave-lengths below 900 meters) are preferable. to reach when they cause interference (ships, airplanes, mobile military stations). A change in this division will be very desirable shortly. As a preliminary suggestion in this respect, without in any way claiming that it should be decisive, the Dutch East Indies Administration recommends that (a) The mixed bands in the 6,000 to 23,000 series should be suppressed, and that these bands should be added to the fixed services. (b) Certain bands in the mobile services should be changed and certain of them should be suppressed; thus 8,550 8,900 (mixed band) to be given to fixed services. 12,825-13,350 (mixed band) to be added to fixed services. 17,100-17,750 (mixed band) to be added to fixed services. 22,300-23,000 (mixed band) to be given to fixed services. 21,550-22,300 (mobile services) to be added to fixed services. The result is given in Fig. 2. The advantages of this change would be: (a) Increase of frequencies for fixed services. (b) A rather more continuous and less complicated spectrum. The number of possible stations on the same basis of 0.1 per cent will be: 922 fixed stations. 239 mobile stations. 76 broadcasting stations. 68 amateur stations. There are also a certain number of other combinations possible.. The Dutch East Indies Administration, although convinced that such changes are not within the competence of the C. C. I. Radio, thinks that the question is so important that— 1. The assembly of the C. C. I. Radio should express a wish that this question may be placed on the program for the next international conference at Madrid in 1932. 2. This question should be submitted to suitable expert reporters. 76 DUTCH EAST INDIAN STATEMENT CONCERNING TOPIC 12 OF THE PROGRAM ALLOCATION OF WAVES TO AVIATION In the experience of the Royal Marine in the Netherland Colonies, waves above 335 kc/s (wave-lengths below 900 meters) are preferable. |