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Реферат: FM Broadcast Radio On The Old 45MHz

Название: FM Broadcast Radio On The Old 45MHz
Раздел: Топики по английскому языку
Тип: реферат Добавлен 06:07:14 25 октября 2010 Похожие работы
Просмотров: 8 Комментариев: 12 Оценило: 2 человек Средний балл: 5 Оценка: неизвестно     Скачать

Band Essay, Research Paper

The old 45MHz FM broadcast band

In 1945 the FCC decided that

FM would have to move from the established

42 – 49 megahertz pre-war band to a new band at 88 – 108 megahertz,

to make way for television.

Both in frequency spectra and

consumer dollars. Therefore, all radios with an FM band

of 88 to 108MHz are post-war.

RCA’s David Sarnoff in particular wanted FM to

“go away” so the public wouldn’t be distracted from

buying his latest up and coming product: televisions. Maybe if

Armstrong said to Sarnoff in the early days

that FM sound would be perfect for the television

soundtrack, they wouldn’t have become rivals.

Turns out modern TV doesn’t even use this spectra.

There was to be a channel 1 here. But co-channel interference

from stations in distant towns would occasionally happen. And

this would be worse for television than FM signals, as FM has

the FM capture ratio working in its favor. FM receivers

will capture a signal that is a few dB stronger than another

co-channel signal, without the weaker signal causing interference.

TV, being an AM type signal with one sideband partially suppressed,

would suffer more severe interference for the same given

signal strengths. Seems odd that the FCC

chose to replace FM with TV in this spectra, but they were more

politically motivated by RCA than scientifically.

Channel 1 was to be used by low power TV stations, and police and fire

users in areas without a channel 1 TV station. Interference to

a TV channel from a fire or police station would be particularly

objectionable when propagation was good.

TV channel 1 was dropped, and land-mobile fire and police now

use this spectra everywhere. These users would sometimes hear distant signals,

as the local signals are usually off.

They do not broadcast continuously like commercial stations.

FM Capture ratio doesn’t help you ignore weaker

signals if your local station isn’t

transmitting. Capture ratio is a feature of FM reception where

the stronger of two FM signals will dominate. The weaker signal

will not be heard at all. Fire and police departments in different

jurisdictions use differing audio tones

to help discriminate between each other. Some older

cordless phones can be heard on these frequencies. Commercial broadcast

would have been a better use of this band.

Because of this reallocation, more than half a million FM

receivers and

some 50 transmitting stations would be

rendered obsolete. One individual consumer once had a 45MHz

FM tuner, a Meissner 9-1047A,

that was also rendered obsolete. It tuned from 41.2 to 50.4MHz. He didn’t

receive any compensation or trade-in offers for his now useless radio he spent

his own money to purchase.

The Yankee Network of 45MHz stations in

New England did not survive the change.

But the worse fear for Edwin Armstrong (inventor of FM) would be a loss

of confidence in FM by the

growing number of faithful hi-fi listeners.

This move to higher frequencies, however, proved to be

only a temporary setback for FM. By 1950 there were over

600 FM stations on the air in the new band.


GE, Westinghouse, Temple and Stromberg Carlson, to

name a few paid patent

royalties to Edwin Armstrong for FM, but RCA wouldn’t.

Armstrong instituted a suit against RCA and NBC charging them with

infringing his five basic FM patents. RCA’s David

Sarnoff figured he could outlast Edwin Armstrong in court in patent

infringement lawsuits. Sarnoff wasn’t thrilled with FM

being selected by the FCC to carry sound for TV. RCA did outlast Armstrong, who went


Philcos with AM, SW, and the old prewar FM band,

marked with FM channel numbers 21 to 99 were made.

A Pilot AM/FM set with the old FM band was made. Note that the

FM band on this set is the old 45MHz band, and that the normal

AM band is also present. Possibly one of the first AM/FM

sets ever produced.

One may see FM radios with band markings from 201 to 300. These

aren’t MHz markings, but FCC channel numbers for the modern 100MHz

FM broadcast band. Channel 201 is 88.1MHz, 202 is 88.3MHz,

259 is 99.7MHz, etc.

Pre-war FM sets may be marked with numbers

like 21 to 99. These are channel numbers for the old 45MHz

FM band.

A partial listing of non-experimental stations on the old 45MHz

FM band. In rough order by state:

K45LA Don Lee Broadcasting System, Los Angeles 44.5

K49LA Hughes Tool Co, Los Angeles, 44.9

KALW Board of Education, San Francisco United School District San Francisco, 42.1

WTIC-FM Travelers B/c Service Corp. (WTIC), (45.3), Hartford W53H

WDRC-FM WDRC Inc. (WDRC), (46.5), Hartford W65H

WINX-FM WINX B/c Co. (WINX), (43.2), Washington DC

WTOP-FM/WHUR Jansky & Bailey, Washington DC 43.2

WOWO-FM Westinghouse Radio Stations (WOWO), (44.9 mc), Ft. Wayne

WABW Associated Broadcasters (WBBW), (47.3 mc), Indianapolis

W45V Evansville On the Air, Inc, Evansville IN, 44.5

W79C Oak Park Realty & Amusement, Chicago 47.9

WBEZ Board of Education, City of Chicago, Chicago, IL 42.5

WWZR/WEFM/WUSN Zenith Chicago W51C 45.1

WIUC University of Illinois, Urbana, IL 42.9

WBKY University of Kentucky, Lexington, KY, 42.9

WBZ-FM Westinghouse Radio Stations (WBZ), (46.7 mc), Boston W67B

WMNE Yankee Network (43.9 mc), Boston

WGTR Yankee Network (WNAC), (44.3 mc), Boston W43B

WMTW-FM Yankee Network, Boston W39B

WBZA-FM Westinghouse Radio Stations (WBZA), (48.1 mc), Springfield

WENA Evening News Assn. (WWJ), (44.5 mc), Detroit

W77XL WJIM Inc, Lansing, 47.7

W81SP Westinghouse Radio Stations, Inc, Springfield MO, 48.1

KMBC-FM Midland B/c Co. (KMBC), (46.5 mc), Kansas City

WFMN Edwin H. Armstrong (44.1 mc), Alpine, NJ

WNBF-FM Wylie B. Jones Adv. Agency (WNBF), (44.9 mc), Binghamton

WQXQ Interstate B/c Co. (WQXR), (45.9 mc), New York

WABF Metropolitan Television Inc. (47.5 mc), New York

WEAF-FM/WNBC-FM National Broadcasting Co, New York 42.6

WABC W67NY Columbia Broadcasting System Inc, NY, 46.7

W99NY Frequency Broadcasting Corp, NY, 49.9

WHNF W63NY Marcus Loew Booking Agency, NY, 46.3

W55NY William G. H. Finch, NY, 45.5

WNYC-FM City of New York, Municipal Broadcasting Co, 43.9

WOR-FM Bamberger Broadcasting Service, New York 43.4, 47.1

WGYN W47NY Muzak Corp, New York, 44.7

WHFM Stromberg-Carlson Co. (WHAM), (45.1 mc), Rochester W51R

WHEF WHEC Inc. (WHEC), (44.7 mc), Rochester W43R

WTAG-FM Telegram Publishing Co, Worcester ???

WGFM General Electric Co. (WGY), (48.5 mc), Schenectady

WBCA Capitol B/c Co. (44.7 mc), Schenectady

WMIT Gordon Gray (WSJS), (44.1 mc), Winston-Salem, NC

WELD RadiOhio Inc. (WBNS), (44.5 mc), Columbus W45CM

WBOE Cleveland City Board of Education, Cleveland, OH 42.5

KYW-FM Westinghouse Radio Stations (KYW), (45.7 mc), Philadelphia

KDKA-FM Westinghouse Radio Stations (KDKA), (47.5 mc), Pittsburgh

W81PH Seaboard Radio Broadcasting Corp, Philadelphia 48.1

WSM-FM National Life & Accident Insurance Co. Nasvhille 44.7

K47SL Radio Service Corp. of Utah, Salt Lake City 44.7

WTMJ-FM Journal Co. (WTMJ), (45.5 mc), Milwaukee W55M

WEBC-FM Head of the Lakes Broadcasting Co, Superior, Wi 43

Source, and more info on early FM is at:

Jeff Miller’s

Broadcasting History Pages

One can use an old mechanically tuned UHF tuner from an

old TV set to act as a downconverter of UHF TV channel sound

carriers to feed into a set with the 45MHz FM band. Connect

a UHF antenna to the tuner input, and a coax cable to the

(usually) RCA jack that is the IF output. And a power supply

to run the tuner. Tune the radio to about 43MHz, and tune

around on the UHF tuner and you should be able to hear the soundtrack of

UHF TV stations of your area on the radio. Also cell phones

around channel 80, but don’t listen to them!

Japan has their FM broadcast band

between 76 and 92MHz. And television channels occupy the rest

of what would be the American FM band.

The Russian FM band goes from 66 to 73MHz.

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.02:40:11 27 августа 2019
.02:40:11 27 августа 2019
.02:40:10 27 августа 2019
.02:40:09 27 августа 2019

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