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This paper presents a simulation study of a cellular highcapacity land-mobile radio system using the hybrid channel assignment scheme with Erlang- C service. The performance of this system in regard to the probability of queueing, the average queueing time, and the average number of queued calls is evaluated and compared with that of the systems employing either the fixed or the dynamic channel assignment scheme.

Since 1969, the Bell System has been conducting continuous rain attenuation experiments on earth-satellite paths. The experiments were carried out at four New Jersey sites by the radio basic research group of the Crawford Hill Laboratory, and at three Georgia sites, two Illinois sites, and two Colorado sites by the radio system engineering group of the Holmdel Laboratory. The measurement frequencies include 11.7, 13.6, 15.5, 17.8, 19, and 28.5 GHz. Interim results of the 10-year (1969–1978) experiments have been published in various technical journals and conference proceedings. For the convenience of system engineers, this paper summarizes the new results and the previously published results and discusses the implications of these data to the design of satellite radio communication systems. The summary includes the geographic dependence, the frequency dependence, the diurnal, monthly, and yearly variations of rain attenuation statistics, the diversity improvement factors, the fade duration distributions, the dynamic rain attenuation behavior, the long-term (20 years) rain rate distribution for U.S. locations, and a simple empirical model for rain attenuation.

Although for nearly four decades BBC radio appeared to be unchanging in a world of change, in recent years “aunty”; has undergone changes perhaps more violent than any other radio system has experienced. Dr. Colle, assistant professor of communication arts at Cornell University, researched this article in Great Britain in 1968.

GERALD PRATLEY has been with the Canadian Broadcasting Corporation since 1946 and at present is film reviewer for Canada's national radio system. His programs, broadcast weekly over the CBC's Trans-Canada and Dominion networks, are This Week at the Movies, The Movie Scene, Facts About Films, and Music From the Films. In addition to his work on films, he is director of both the Toronto Film Society and the Canadian Film Institute. He also contributes reviews to The Critic and Canadian Film News.

The effects of fading on the error-rate performance of a multihop line-of-sight PCM radio system, operated with or without diversity, are theoretically analyzed. A set of approximate formulas for the distribution of error probability has been established. These formulas can be used to determine the necessary carrier-to-noise power ratio in a noncoherent frequency-shift keying or coherent phase-shift keying system in order to meet the specified error probability and percent outage time.

A terminal for transmitting digital signals over TD-2 microwave radio relay routes has been designed and evaluated in a recent field trial. This paper details some of the radio system characteristics which influenced the design, describes the major features of the terminal, and reports the trial results. The terminal will be used in the toll network to provide intercity Picturephone® trunks and data circuits.

Starting from the general requirements imposed on the transmitting medium, this paper discusses the engineering of a radio system for television purposes and describes the radio facilities actually employed for the recent Bell System demonstration. The tests to which the system was submitted to determine its suitability are outlined and the measured frequency-response characteristics are shown. An interesting phenomenon due to multi-path transmission, the production of positive and negative secondary images, is reported. A brief series of experiments concerned with the transmission of both voice and image “on a single wave-length” is also described.

Winter floods in the willamette river Basin in Western Oregon wreak havoc and destruction from frequent flooding of a highly-populated and developed valley, 150 miles in length. Congress instructed the United States Corps of Engineers (USCE) to study the problem in the Willamette Valley and to make specific recommendations. As a result the Corps has recommended a system of 16 multiple-purpose reservoirs. These reservoirs were to be located on the major tributaries in the basin and would control a total of 3,200 square miles of the 11,200 square miles in the basin. At the present time five of the recommended reservoirs are in operation, two are under construction, and planning is under way on two more.

RADIO noise is the result of interaction among four components of the airplane, namely, electrical equipment, the radio receiver, the electric wiring, and the antennas. These components are produced by three different groups of manufacturers who have until recently made no effort to co-ordinate with each other on the radio-noise problem, the solution of which requires that these components be considered conjointly and that each party accept his part of the total responsibility. Until recently, this joint responsibility was not recognized, but each party was held to a rigid set of specifications which restricted them all to a very narrow line of behavior and made them responsible only for the meeting of some specific requirements. As a consequence, the various manufacturers considered their obligation as fulfilled when these specific requirements were met, whether the radio system was noise-free or not.

The l-2 control terminal which is described in this paper, is a basic element in a complete ?package? radio system. The system design is building block in nature with only a few building blocks required for a complete operating system that is devoid of frequently unnecessary embellishments. However, additional panels are available where more than the basic functions are required.

The bell telephone laboratories, inc., have recently completed the development of a microwave radio system to operate in the 11-kmc (kilomegacycle) band. The system is coded TJ and is designed for short-haul and medium-haul systems. One of the first systems was installed between Flagstaff and Phoenix, Ariz. It is hoped that a description of the system may be of interest to other engineers in the communications industry.

1. The UWL “Helgoland” system has been built with the rough sea conditions in the Southern North Sea in mind: wave periods up to 8 sec, wave heights up to 8 m, tidal currents up to 1 m/sec. 2. The main body can be towed at a velocity of up to 5 knots, and be lowered without the assistance of a floating crane. The system has a high degree of flexibility. 3. In order to withstand the oscillating forces caused by sea movements, a horizontal cylinder was chosen as main body. The main body is ballasted to a negative buoyancy of 16 t (more than for other comparable UWL systems). Four swords stabilize the UWL against horizontal forces. The main body acts as a self-righting body. 4. Emergency supply of food and energy allows complete surface independence for 10 days. 5. Rough surface conditions and poor underwater visibilities do not allow aquanaut activities on the sea bottom to be observed from the surface. A wireless system is used for diver communication on the sea bottom. Three communication systems connect the UWL main body to the supervising station on land: one TV and two radio systems. One radio system is used to transmit alarms to the land base, the other will be used in 1973 as transmission system for oceanological data. 6. Aquanauts cannot be transported from the habitat to the deck decompression chamber (DDC) during rough weather. Hence one room in the UWL main body serves as decompression chamber. 7. The surface energy station, a floating buoy, is a world first. The station operates automatically; it is controlled by aquanauts in the UWL. Electricity, compressed respiratory gases and fresh water are transported from the buoy to the UWL via an umbilical line. Due to tide and wave motion, the umbilical line is shaped in goose-neck fashion. Other suplies such as food and mail are brought to the UWL by supply containers without assistance from surface divers. Supplementary respiratory gas for the semi-closed diving apparatus is stored on the sea bottom; the same applies for nitrogen. 8. The first manned test period in August, 1969, and the subsequent 9-month unmanned period proved that the system is able to withstand rough sea conditions. 9. As a research base, UWL “Helgoland” has met the expectations. It is possible to work and to conduct research in the sea, even under the adverse conditions prevailing in the North Sea. In 1973, UWL “Helgoland” will operate again on the sea bottom near Helgoland.

This paper reports a two-hop system experiment, designed to demonstrate the viability of the concept described in previous papers. A single RF channel, instrumented in the 11 GHz common carrier band, is transmitted from a terminal to a repeater one and a half miles away. After passing through the repeater, the signal is transmitted back to the terminal. We discuss the system parameters in relation to the requirements of operation at frequencies above 10 GHz; we also describe design, construction, and performance, as well as the lessons learned from one year of operation.

This paper describes new variolosser circuits which are suitable for use in high quality broadband IF amplifiers operating at several hundred MHz, and offering substantial improvements in power consumption, temperature stability, bandshape stability, minimum attenuation and attenuation range. Three variolossers of this type are used in the automatic gain control for the IF amplifier used in the short hop radio system experiment. We present an analysis, a design procedure, and extensive measurements. As an example of the performance to be expected, one experimental vario-loser has a minimum attenuation of 1.35 dB, a maximum attenuation of 19.5 dB, and is flat to ±0.15 dB over a 40 percent band centered at 300 MHz.

The recently developed lenkurt type 74A microwave system is designed for a capacity of 240 telephone channels per radio circuit over short-haul routes. Economic considerations in systems planning were based upon achieving a cost per circuit-mile which would compare favorably with new toll cable installations. Fig. 1 shows two views of a basic terminal.

At the beginning of and during the war with Japan, the wide expansion of operations in the Pacific Theater over-taxed the Navy's radio communications to a point where the need of additional communication channels became acute. The adaptation of a 4-channel Western Union type multiplex to a single-channel frequency-shift radio system appeared to be the most logical way to solve this problem quickly. Improvements in the radio and the use of the multiplex enabled the Navy to set up communication channels between the United States and all the principal naval bases in the Pacific. A 4-channel circuit was established between Washington, D. C., and Honolulu, T. H., and San Francisco, Calif., and Honolulu within approximately nine months after the beginning of initial tests. Other systems followed in close succession.

Development of radio and electronic equipment for telemetering weather data from remote inaccessible locations has been greatly accelerated in recent years. In 1959 the Bonneville Power Administration completed the installation of an automatic precipitation-and temperature-reporting system utilizing standard detection devices, and including a unique telemetering and transmission system. This system was installed above the Hungry Horse Reservoir located on the south fork of the Flathead River in Montana. The Hungry Horse Reservoir, which was built by the Bureau of Reclamation in 1953, has a storage capacity of 3,500,000 acre-feet, of which nearly 3,000,000 are usable for power production. The Hungry Horse Project is designed primarily to increase system prime power on the U. S. Columbia River System and to control floods in the Flathead Valley in the vicinity of Kalispell, Mont., and on the main Columbia River farther downstream.

A radio system for upper-air weather soundings with small unmanned balloons is described. The balloon instrument comprises elements for measuring pressure, temperature, and humidity, and a miniature radio transmitter; the latter converts the response of the measuring instruments into characteristic signals modulating the emitted radio wave and sends this wave to a ground station where the signals are measured and recorded. Details of the system are given and a discussion is given of the accuracy of the upper-air observations obtained and of the tolerances permissible for component elements of the system.

This paper describes a V. H. F. radio system designed to provide communications for a Main Line railroad. It consists of 21 base stations, in 3 divisions; the stations in each division are connected by microwave channels to a District Dispatcher's office, and to a Hot Box Detection Center at one end of the line and communicating to Trains and Maintenance-of-Way crews.

THE southwest coast line of Oregon is rugged, primitive, and beautiful. From Gold Beach, near the Oregon-California border, the towns of Port Orford, Bandon, Coos Bay, Reedsport, and Mapleton lie on the sea at the foot of the coast range in a northward sweep of 144 miles.

In order to supply additional mobile-radio-telephone service to the public in the greater Los Angeles area, The Pacific Telephone and Telegraph Company applied for four 450-mc (megacycle) radio channels in June 1956. At that time there were only six channels available for the domestic public mobile-telephone service (MTS) in the 450?460-mc common-carrier radio-frequency (r-f) band.

This paper considers the noise which is introduced into the individual channels of a multichannel telephone system (frequency division multiplex) during transmission over a v.h.f. f.m. radio system due to various forms of distortion in the radio system. Formulae and curves are given for the computation of noise levels in systems of up to 60 channels and methods of measuring the parameters used in these formulae are discussed.

A six-hop radio system employing line-of-sight, diffraction, and tropospheric propagation modes, in the 4.4- to 5.0GHz band, has been installed in Korea. Received carrier levels and teleprinter error rates were recorded and analyzed, and the results extrapolated to predict minimum performance for 99 percent of all hours of the year. The carrier level measurements for the troposcatter links indicated more extreme seasonal variations than predicted by the NBS method. In measurements of the teleprinter error rates on the troposcatter links, it was found that for both dual and quadruple diversity, the advantage of pre-detection over postdetection combining was 4 to 6 dB for a teleprinter character-error-rate of 1 in 10 000.

This paper describes briefly the Western Electric type TJ microwave Radio System designed for operation in the 10.7 to ll.7-kMc frequency allocation, and covers the performance of this system since it was placed in service across Chesapeake Bay on February 1, 1959. This is the first TJ system to be placed in service in the territory of The Chesapeake and Potomac Telephone Company of Virginia, and operates between Hampton and Kiptopeke, Va., a distance of 22.5 statute miles. The over-water portion of this path has a length of 18.5 miles.

This paper points out the salient equipment and building considerations peculiar to the TH-3 radio system with emphasis on the ability to combine TH-3 with existing radio systems.

THIS paper presents a description of a radio system now operating between Seattle, Wash., and Victoria, British Columbia. The radio system employs the Lenkurt 72A equipment, the predecessor of the Lenkurt 72B radio described in an unpublished paper by Harp and Kebby of the Lenkurt Company. This application of 72A radio makes use of 33C Lenkurt carrier with a capacity of 24 channels in comparison to the Lenkurt-45-class carrier used with the 72B radio and having a capacity of 72 channels. The base band of the 72A is 160 kc as contrasted to the '300-kc base band of the 72B.

This article discusses the considerations governing the general over-all physical arrangements of the TH system, which lead to differing treatments for the radio equipment, FM terminals, and protection switching equipment. It describes the general mechanical features of these divisions, from the sliding-rack bay used for the radio equipment to the extensive use of plug-in units for protection switching.

GERALD PRATLEY has been with the Canadian Broadcasting Corporation since 1946 and at present is a film commentator and writer for Canada's national radio system. He has recently started a new series of Music from the Films broadcast weekly over the CBS's Trans-Canada network. In addition to his work on films, he is director of both the Toronto Film Society and the Canadian Film Institute. He also contributes reviews to The Critic and Canadian Film News.

To maintain the high performance objectives of the TH radio system under operating conditions requires the regular use of accurate field test equipment. The necessary test instruments are incorporated into mobile test consoles, one for each major subdivision of the TH system. Three of these are described in some detail in this article: 1) the broadband radio transmitter-receiver test set: 2) the FM terminal test set: and 3) the protection switching test set.

ALL essential data on operation, performance and stresses of a new‐model aircraft in flight test are picked up, transmitted and recorded automatically by a radio system developed and built by Vultec Aircraft Inc., of Downey, California. The indications of seventy‐two different instruments in the machine can be transmitted a distance of about 100 miles and recorded simultaneously at a ground station at a maximum speed of 100 instrument readings per second.

A miami-havana radio system, consisting of the wide-band over-the-horizon system discussed in another paper,1 together with TD-2 microwave links at each end, has recently been placed in service. This paper discusses the overall radio system, its method of operation, and some of the test results obtained during its initial line-up.

The paper describes a simplified procedure based on the use of the FCC F(50,50) signal strength charts to provide an approximate determination of the statistical coverage contours for a UHF base-to-mobile radio system operating over irregular terrain. Appropriate adjustments are included in the procedure to account for mobile antenna height-gain variations, signal strength reduction due to shrubbery, trees, etc. in the immediate vicinity of the mobile units, signal strength reduction due to terrain variations differing from a Δ h of 50 meters, and signal probability requirements differing from 50 percent. Procedures are also discussed for estimating the net signal-strength probability characteristics due to two or more contours of known probability.

Powered vehicles in industrial environments have long been accepted and their safety considerations have become standard. Low-speed, unmanned vehicles are now being introduced to office and similar situations, requiring a new approach to safety considerations. This paper describes a low-frequency radio system for collision avoidance.