Search

Three salient factors governing attenuation of 11-GHz waves propagating through rain on a terrestrial radio path are discussed: magnitude of attenuation as a function of rain rate, relationship between attenuation and path length, and dependence of attenuation on polarization. Background material is given pertinent to the companion papers in this issue which develop procedures useful for radio system design.

Four of the Bell System digital transmission systems, T1 Outstate, T2, 3A-RDS (radio system at TS rate), and T4M, have violation monitor and removers (vmrs) located at the receiving-end maintenance offices. Among other things, they monitor the lines, remove violations in the pulse transmission code, and generate alarms to initiate maintenance actions. This paper investigates the alarm statistics of the four types of vmr under the assumption that the information bits are statistically independent. It is found that all the vmrs have very sharp alarm thresholds. The results of the T4M vmr are presented in detail. Curves are given to show the various statistics obtained.

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.

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.

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.

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 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.

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.