. The Bell System technical journal . a total of fifteen small condensers across the main condenserof the transmitter oscillator shifts the frequency in steps over anadjustable range. The contactor is rotated at the rate of nine re\-o-lutions a minute, which is sufficiently slow to show definite steps inthe oscillograph record. At the receiving end a local oscillator sup-plies a radio-frequency wave for beating the incoming frequenciesdown to values within the audible range. A long oscillograph record of this stepped frequency gives a sortof moving picture of the fading for the entire band cov
. The Bell System technical journal . a total of fifteen small condensers across the main condenserof the transmitter oscillator shifts the frequency in steps over anadjustable range. The contactor is rotated at the rate of nine re\-o-lutions a minute, which is sufficiently slow to show definite steps inthe oscillograph record. At the receiving end a local oscillator sup-plies a radio-frequency wave for beating the incoming frequenciesdown to values within the audible range. A long oscillograph record of this stepped frequency gives a sortof moving picture of the fading for the entire band covered. Asample of such a record is shown in Fig. 17 with alternate picturesin the series removed to simplify the relations, since by reason of. Fig. 17—Sample band fading record the two-way traversal of the frequency band successive picturesare reversed. If a series of such built-up pictures as these could betaken rapidly on moving picture film, and projected successivelyupon a screen we should have before us an animated view of bandfading. And according to the results of experimental investigationthe subject offers a lively theme for such a presentation. The peaksand depressions glide nervously back and forth across the successive pictures of Fig. 17 (which, by the way, weie selectedfor their half-tone reproduction possibilities rather than as firstclass examples of the records taken) illustrate a rather leisurelymovement of this sort. These ten built-up photographs cover aperiod of slightly more than one minute. In the first seven picturesa depression appears at the left, while in the last three this depressionseems to have made an exit followed by the simultaneous entrance ofanother from the opposite wing of
Size: 2166px × 1154px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
