Bell telephone magazine (1922) (14568436260)

Identifier: belltelephonemag00vol2930amerrich (find matches)

Title: Bell telephone magazine

Year: 1922 (1920s)

Authors: American Telephone and Telegraph Company American Telephone and Telegraph Company. Information Dept

Subjects: Telephone

Publisher: (New York, American Telephone and Telegraph Co., etc.)

Contributing Library: Prelinger Library

Digitizing Sponsor: Internet Archive

Text Appearing Before Image:

ons for usingthese frequencies is that television cir-cuits or large numbers of telephonecircuits need a very broad frequencyband—three or four million cycles ormore in width. In order to find spacein the spectrum where bands severalmillion cycles wide could be obtained,it was necessary to turn to the micro-wave frequencies. Selecting a Route A small army of people must co-ordinate their efforts in order to es- 1ZO Bell Telephone Magazine winter tablish a radio relay system. Once a must be taken into account in finding decision is reached to build such a line-of-sight paths, it is natural to system, engineers study the topog- seek elevated sites for repeater sta- raphy of the ground, using the best tions in order to extend the distance maps available, and pick a tentative between them and thus minimize the route.* Since the earths curvature number of stations required. Hill-tops are likely to make good repeater • See Radio Relay and Other Special Buildin*:-, Magazine, Spring 1950.

Text Appearing After Image:

The steel skeleton tone)- supports the an-tennas o>i its summity and carries theconnecting plumbing to them; the housecontains the radio equipment, the powersupply, and the emergency generator station locations. Elevations are de-sirable that will permit sending theradio frequencies about 30 miles onthe average. Remembering that the radio equip-ment has to be cared for, a site whichis inaccessible during the wintermonths will probably not be satisfac-tory, despite any other advantages itmay have. Remembering, too, thatmicrowave frequencies can be re-flected, relatively flat sections of theearths surface—including water-covered areas—must be avoided orelse crossed in such a way that, if re-flections do occur, no serious harmwill be done. When the map work is complete,crews go into the field to study thelocations selected from the maps. Insome areas, the only maps availableare based on surveys made more than60 years ago. In several cases, hillsappearing on these maps were found,o

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1922

Prelinger Library

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