. Il giornale tecnico Bell System m antenne sul tetto del Long LinesBuilding, 32 Avenue of the Americas, New York City. Queste antenne 450 piedi sopra terra. Uno degli attuali trans-mitter Mobile Service è stato utilizzato per i test 150-mc. Trasmissioni sperimentali speciali sono state allestite per i test 450, 900 e 3700-mc. Tutti erano capaci di modulazione in frequenza. L'unità mobile era un carro di stazione equipaggiato per ricevere e misurare segnali alle varie frequenze. L'apparecchiatura di ricezione era ar-varied per conversione rapida da 150 a 450 a 900 mc. La larghezza di banda (circa 50 kc) e il sistema
1260 x 1984 px | 21,3 x 33,6 cm | 8,4 x 13,2 inches | 150dpi
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. The Bell System technical journal . m antennas on the roof of the Long LinesBuilding, 32 Avenue of the Americas, New York City. These antennaswxre 450 feet above ground. One of the existing Mobile Service trans-mitters served for the 150-mc tests. Special experimental transmitterswere set up for the 450, 900, and 3700-mc tests. All were capable offrequency modulation. The mobile unit was a station wagon equipped to receive and measur-signals at the various frequencies. The receiving equipment was ar-ranged for rapid conversion from 150 to 450 to 900 mc. The bandwidth(about 50 kc) and system modulation (±10 kc) were identi(;al at allthree freciuencies (equal to the existing standards at 150 mc). The 3700-mc tests were handled separately. It was not possible to employ thesame bandwidth and deviation, but this does not invalidate the com-parison of signal propagation at the Aarious frequencies. A most useful tool in making these measurements was a device knownas a Level Distribution Recorder, or simply LDR. This was built. miomo CD lO a, ■ 1074 MOBILE RADIO TRANSMISSION 1075 especially for these tests and is similar to its foieninners which havebeen used in the past for measuring- atmospheric static noise. Tlie LDR, in combination with a caliliiated radio r(Meiver, is capable of taking asmany as twenty instantaneous sami)les of radio sij>;nal str(Mif>;th per sec-ond, sorting the samples by amplitude, and rendering infoiination on abatch of samples from which a statistical distribution (•ure can beplotted. The LDR was also us(xl for measuiing the statistical distributionof audio noise in the output of the radio receiver. The LDR was, in thiscase, associated with a special con-erter whose characteristics resemblethose of a 2B noise measuring set. No arrangements were made for measuring radio proi)agation frommobile unit to a land receiver. It was felt that the comparison by fre-quencies woidd be substantially the same as in the outward directionof transmiss
