File:The Bell System technical journal (1922) (14569525057).jpg

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English:

Identifier: bellsystemtechni18amerrich (find matches)
Title: The Bell System technical journal
Year: 1922 (1920s)
Authors: American Telephone and Telegraph Company
Subjects: Telecommunication Electric engineering Communication Electronics Science Technology
Publisher: (Short Hills, N.J., etc., American Telephone and Telegraph Co.)
Contributing Library: Prelinger Library
Digitizing Sponsor: Internet Archive

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made per second isimportant only when considering small altitudes. The height whichgives a value of unity for F^ corresponding to a frequency meter signalof IFm cycles per second is the minimum height which can be indicatedsince lower altitudes give the same reading. Lower altitudes causeonly a fraction of a cycle of frequency, Fd, to be generated per sweep,but since this fraction is repeated 2Fm times per second, it constitutesa signal of the same frequency 2Fm and is so counted by the frequencymeter. In order to make this minimum altitude small, it is necessarythat AF be large, since they are inversely proportional to each other.A frequency sweep of approximately 25 megacycles is required toprovide measurements down to the present minimum of about twentyfeet. If a high antenna efficiency is to be obtained over a band 25megacycles wide, it is necessary that the percentage variation from theaverage frequency during the modulation cycle be small. This A TERRAIN CLEARANCE INDICATOR 229
Text Appearing After Image:
be 230 BELL SYSTEM TECHNICAL JOURNAL percentage variation is made small by the use of an average frequencyof approximately 450 megacycles. The use of this ultra-high fre-quency has the additional advantage that the antennas can be bothsmall and efficient and cause little drag upon the airplane. Apparatus Figure 3 is a photograph of all the units of the altimeter, with theexception of the transmission lines used to connect the antennas totheir respective units. The units are as follows: left to right, receiver,power unit, and transmitter, with a junction box in the upper right.In the foreground are the two dipole antennas and the indicating meterwith its range-shift switch. The meter and one of these antennas areshown in larger scale in Fig, 4. The meter has two scales, the upper

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https://www.flickr.com/photos/internetarchivebookimages/14569525057/

Author Internet Archive Book Images
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Flickr tags
InfoField
  • bookid:bellsystemtechni18amerrich
  • bookyear:1922
  • bookdecade:1920
  • bookcentury:1900
  • bookauthor:American_Telephone_and_Telegraph_Company
  • booksubject:Telecommunication
  • booksubject:Electric_engineering
  • booksubject:Communication
  • booksubject:Electronics
  • booksubject:Science
  • booksubject:Technology
  • bookpublisher:_Short_Hills__N_J___etc___American_Telephone_and_Telegraph_Co__
  • bookcontributor:Prelinger_Library
  • booksponsor:Internet_Archive
  • bookleafnumber:246
  • bookcollection:prelinger_library
  • bookcollection:additional_collections
  • bookcollection:americana
  • BHL Collection
Flickr posted date
InfoField
27 July 2014



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current22:00, 26 August 2017Thumbnail for version as of 22:00, 26 August 20172,496 × 1,466 (1.52 MB)SteinsplitterBot (talk | contribs)Bot: Image rotated by 90°
14:06, 23 September 2015Thumbnail for version as of 14:06, 23 September 20151,466 × 2,504 (1.49 MB)Fæ (talk | contribs)== {{int:filedesc}} == {{information |description={{en|1=<br> '''Identifier''': bellsystemtechni18amerrich ([https://commons.wikimedia.org/w/index.php?title=Special%3ASearch&profile=default&fulltext=Search&search=insource%3A%2Fbellsystemtechni18amerric...

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