NAB reports (Jan-Dec 1934)

Record Details:

Title:
NAB reports
Date:
Jan-Dec 1934
Publisher:
Washington D.C. : National Association of Broadcasters
Volume:
NAB reports (Jan-Dec 1934)
Leaf #:
000323
Language:
English
Subjects:
Broadcasters’ news bulletin, NAB member service","Radio broadcasting -- United States – Periodicals","Radio -- Law and legislation -- United States – Periodicals","Television broadcasting -- United States -- Periodicals","Television -- Law and legislation -- United States – Periodicals","National Association of Broadcasters -- Periodicals
Collection:
Broadcasting & Recorded Sound
Format:
Periodicals
Contributor:
University of Maryland College Park
Sponsor:
University of Maryland College Park
Coordinator:
Media History Digital Library
Date Added:
December 07, 2023
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and depict the net over-all result from the input to the recording amplifier to the output of the pickup. The curves on audio harmonic content are shown in Figure 1. The difference in harmonic content shown between transmitters of “composite” design and those of “standard” make should not be taken as either a disparagement of one or a recommendation of the other. The difference is accounted for by reason of the fact that the majority of composite transmitters were high-level modulated, and since, in most cases, the designers were not so sure of their ground, they installed a surplus of modulator capacity. On the other hand, almost all of the standard transmitters were of a type and design employing low-level modulation and two “linear” stages with tubes worked right up to their limit. In some power classifications, the tube used in the final amplifier was admittedly not capable of delivering the rated power fully modu¬ lated. Such a transmitter is difficult to keep properly adjusted with the checking and maintenance equipment usually available, which consists of a voltmeter and pocket knife both furnished by the operator. In passing, it might be noted that over-modulation was found to be very prevalent, especially among the composite transmitter group. In view of the interest among stations in Class B modulation, there is included in Figure 1 a curve (D showing the average dis¬ tortion in 8 transmitters so modulated. TABLE NO. 1 Composite Transmitters No. Power Modulation No ; Power Modulation 1 100 High 13 • 100 High 2 2S0 High 14 SOO High 3 1000 Low IS 250 Low 4 SOO High 16 100 High S 100 High 17 SOO High 6 1000 Low 18 SOO Low 7 2S0 Low 19 100 High S 100 High 20 100 High 9 100 High 21 100 Low 10 1000 Low 22 100 Low 11 SOO Low 23 100 High 12 500 High 24 100 Low Standard Transmitters No. Power Modulation No. Power Modulation 25 1000 High 31 2S0 High 26 5000 Low 32 SOO Low 27 100 Low 33 SOO Low 28 2 SOO Low •34 ' 1000 Low 29 1000 Low 35 250 Low 30 5000 Low 36 1000 Low TABLE NO. 2 Composite Equipment FREQUENCY Station No. 40 SO 60 80 100 200 500 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 1 + 2.0 + 2.0 -j 1.5 + 1.0 0 0 0 0 0 +1.0 —1.0 — 4.5 —11.0 —16.0 2 4 0.5 + 1.0 + 1.0 +1.0 +1.0 0 0 0 0 0 + 1.0 + 1.5 + 2.0 + 2.5 + 4.0 + 2.0 0 3 — s.o — 4.0 — 3.0 —1.0 0 0 0 0 0 0 0 — 3.0 — 6.0 — 7.0 — 8.0 4 —10.0 — 8.0 —6.0 —5.0 —2.0 —1.0 0 0 0 —1.0 — 4.0 —10.0 S — 3.0 — 2.0 —1.5 —1.0 0 0 0 0 0 +0.5 0 + 1.0 0 0 — 1.0 —3.0 6 0 + 6.0 +5.0 +3.5 0 0 0 0 +1.5 +2.5 + 3.5 + 2.0 — 6.0 7 —18.0 —12.0 —8.0 —6.0 —3.0 —1.5 0 0 0 —1.0 — 5.0 — 8.0 8 — 4.0 — 3.0 — 2.0 —1.0 —1.0 0 0 0 0 0 0 — 1.0 — 3.0 — 8.0 —13.0 9 — 3.0 — 0.5 — 3.0 —4.0 —3.0 —2.0 0 0 0 0 0 0 — 0.5 — 0.5 — 2.0 — 3.0 — 1.0 10 0 + i-o + 1.0 +0.75 +0.5 0 0 0 —1.5 —4.0 —8.0 —12.0 —16.0 11 0 -r 1.0 — 2.0 —2.0 —1.0 0 0 0 0 —1.0 —1.0 — 4.5 —12.0 12 — 9.0 — 6.0 —4.0 —3.0 —1.0 0 0 0 0 0 0 — 2.5 —10.0 13 — 2.0 — 2.5 — 3.0 —2.2 —2.2 —2.0 0 0 0 0 0 — 1.0 — 1.0 — 1.0 — 1.5 14 0 -) O.S + 1.0 +0.5 +0.5 0 0 0 0 0 0 0 • 0 — 1.0 — 1.0 — 2.0 —3.5 IS — 4.0 — 3.0 — 2.5 —2.0 —1.0 0 0 0 0 0 —1.0 — 3.0 — 5.0 — 9.0 16 — S.O — 4.S — 4.0 —3.0 —3.0 —1.5 0 0 0 +3.0 +4.0 + 4.5 + 4.0 + 3.0 + 2.0 17 — 9.0 — 8.0 — 7.0 —5.0 —4.0 —2.0 0 0 0 0 —2.0 — 3.0 — 5.0 18 —10.0 — 7.25 — 5.5 —2.0 —0.75 0 0 0 + 1.0 + 1.0 —0.5 — 2.75 — 6.0 —10.0 19 — 8.0 — 6.0 — 4.5 —3.0 —2.0 —0.5 0 0 0 —2.0 —3.0 — 4.5 — 6.0 — 7.5 — 9.0 —10.25 20 —9.5 —6.0 —1.0 0 0 0 —0.25 —1.25 — 3.5 — 7.0 21 — S.O —2.5 —1.5 0 0 0 —1.5 —1.0 0 — 8.0 22 —8.0 —6.5 —2.0 0 0 0 0 0 — 1.0 — 5.0 —10.75 23 — 5.0 — 3.5 —2.75 —1.25 0 0 0 0 0 0 0 0 — 1.0 — 1.1 — 1.5 —9.0 24 N. Station — 0.5 B.— No. — 0.25 0 0 0 0 0 0 0 —O.S 24 transmitter only without studio equipment. Standard Equipment —1.7 — 2.5 — 3.25 — 4.7 — 6.0 — 8.5 No. 40 50 60 80 100 200 500 1000 2000 3000 4000 ■ 5000 6000 7000 8000 9000 10000 25 — 3.0 — 2.0 — 2.0 —1.5 —1.25 0 0 0 0 0 0 0 0 0 0 — 1.0 —2.0 26 — 8.0 — 6.0 — 4.0 —2.0 —1.5 —1.25 0 0 + 1.0 +2.0 +1.0 0 — 1.0 — 3.0 —10.0 27 — 3.0 — 2.0 — 1.5 —0.75 0 0 0 0 0 0 0 0 0 0 0 — 0.5 —1.0 28 29 30 —11.0 — 8.5 — 5.0 —3.0 —2.0 0 0 0 0 0 —1.0 — 6.0 —12.0 —19.0 — 6.0 — 3.0 —2.5 —1.5 0 0 0 0 0 0 0 0 — 1.0 — 1.0 — 2.0 31 — 6.0 — 5.5 — 5.0 —1.5 0 0 0 0 0 0 0 0 — 2.5 — 3.0 — 1.0 32 — 8.0 — 4.75 — 3.5 — 1.5 0 0 0 -{“0.5 + 1.25 — 2.0 0 — 3.8 —10.0 33 — 4.0 — 1.5 —1.5 —1.5 — 0. / 5 0 0 + 1.0 +2.0 +3.0 — 2.0 — 3.50 —10.0 34 — 3.0 — 1.75 — 1.0 — 0.73 — 0.3 0 0 0 0 0 0 0 — 1.25 — 4.0 — 7.0 —10.0 35 — 9.S — 7.5 — 5.0 —3.75 —1.25 0 0 0 +0.5 + 1.5 +2.25 + 1.0 — 2.0 — 6.0 36 — 1.0 -) 5.0 + 3.25 +1.25 +0.25 0 0 0 +0.5 +2.0 + 3.5 + 2.0 + 0.75 — 1.5 — 2.75 —5.0 • Page 383 •