"F-M" Put on Commercial Basis August/September
1940 National Radio News Article
Aug/Sep 1940 National Radio News
of Contents] These articles are scanned and OCRed from old editions of the National Radio Newsmagazine. Here is a list of the
National Radio News articles I have already posted. All copyrights are hereby acknowledged.
Edwin H. Armstrong demonstrated the viability of FM
(frequency modulation) for long distance broadcasting
in January of 1940, the U.S. FCC (Federal Communications
Commission) allocated spectrum to it in the 42-50 MHz band. Armstrong
had introduced the FCC to FM originally in 1936. The new modulation scheme was popular
due to its immunity to amplitude related noise like that generated by motors,
automobile ignition systems, and lightning.
However, World War II broke out a little over a year later and most commercial
radio advancements were put on hold. This article from a 1940 edition of National
Radio News could not have predicted that, or the FCC's decision to relocate
the FM spectrum to 88-108 MHz in 1945 in the closing days of WWII. Some speculate
that the spectrum shift was a ploy by RCA chairman
David Sarnoff to undermine the advantage Armstrong had with
his established FM radio production. Nah, it couldn't be so because government bureaucrats
have never done favors for the benefit of friends/acquaintances for political favor
"F-M" Put on Commercial Basis
This article was released to National Radio News by the Federal Communications
Commission, Washington, D. C.
Hailing frequency modulation as "one of the most significant" contributions to
radio in recent years and declaring that f-m broadcasting on a commercial basis
is desirable in the public interest, the Federal Communications Commission recently
announced the availability of the frequency band of 42,000 to 50,000 kilocycles
for that purpose. This will provide 40 f-m channels, each 200 kilocycles wide -
35 to regular high-frequency broadcast stations and 5 to noncommercial educational
"Frequency modulation is highly developed," declares the Commission in unanimous
report. "It is ready to move forward on a broad scale and on a full commercial basis.
On this point there is complete agreement among the engineers of both the manufacturing
and the broadcasting industries. A substantial demand for f-m transmitting stations
for full operation exists today. A comparable public demand for receiving sets is
predicted. It can be expected, therefore, that this advancement in the broadcast
an will create employment for thousands of person in the manufacturing, installation
and maintenance of transmitting and receiving equipment and the programming of such
At the same time the Commission points out that there was agreement among witnesses
at its recent hearing that this new service will not supplant the service of standard
broadcast stations generally and that, therefore. f-m will not make obsolete the
receiver now in use. Standard broadcasting is on an entirely different frequency
band from that to be occupied by frequency modulation. F-m will not interfere with
it. Present standard broadcasting will continue, and certainly for a number of years
will render full service. The extent to which in future years the listeners will
be attracted away from the standard band cannot be predicted. Testimony at the hearing
indicated that manufacturers will provide receiving sets capable of receiving both
The chief claims for f-m are that it gives more fidelity and less interference
than standard broadcast. The principle of frequency modulation has long been known
but it practical use was not demonstrated until recently.
There was unanimous agreement at the March hearing that f-m is superior to amplitude
modulation for broadcasting on frequencies above 25,000 kilocycles. The use of a
wide band of frequencies makes possible a reduction of noise to a greater extent
than attained with narrow-band standard broadcast. There was testimony that a band
width of less than 200 kilocycles can be used for f-m, but this lessens the noise-discriminating
quality which has been established by experimental operation with the wide channel.
Testimony advocating the narrower band width was not supported by experience in
program service. Moreover, the narrower band width would jeopardize use of facsimile
transmission on the same channel. The Commission believes that regular program service
should begin on a 200-kilocycle band basis which can be conveniently reduced if
developments warrant. By adopting the wide-band f-m channels at this time, it will
be possible for the public to continue the use of receivers designed for wide-band
reception even though narrower channels may later be authorized.
The opening of a new band for commercial broadcast will help to correct numerous
defects and inequalities now existing in the standard broadcast system. These inequalities
result from the scarcity of frequencies, their technical characteristics, and the
early growth of broadcasting without technical regulation. There is today a lack
of stations in some communities, and other communities do not have sufficient choice
of program service. The establishment of the new broadcast band in the higher frequencies
will enable many communities to have their own broadcast stations.
Experimental operations show that f-m stations can operate on the same channel
without objectionable interference with much less mileage than is possible with
standard broadcast stations. F-m has the ability to exclude all except the strongest
signal Also, f-m stations require much less mileage separation than do standard
broadcast stations. The service range of f-m stations, though limited, will in many
cases be greater than obtained from the primary service of comparable standard broadcast
The licensing of classes of standard broadcast stations in the same area with
different frequencies and different power has resulted in a wide disparity in the
extent of service to the public. The system of classification now employed for standard
broadcast stations will not be used for f-m stations. The rules and regulations
and engineering standards to be issued for f-m in the near future will enable applications
to be made for facilities to serve a specified area. F-m stations will be rated
on the basis of coverage rather than power. Competitive stations in the same center
of population will be licensed to serve the same area.
The present situation of certain standard broadcast stations having large daytime
coverage and restricted nighttime coverage on duplicated channels will be avoided.
The coverage of f-m stations will be substantially the same both day and night.
However, f-m stations do not have the long-distance coverage of the present high-powered
clear-channel standard broadcast stations. The latter may be required indefinitely,
for widespread rural coverage, But for covering centers of population and trade
areas, the new class of station offers a distinct improvement.
The Commission deems it in the public interest to allocate a contiguous band
of frequencies to accommodate both commercial and educational f-m stations. The
band between 42,000 and 50,000 kilocycles is particularly suited for this service.
Under the new allocation, the same number of frequencies heretofore assigned to
non-commercial educational stations has been retained, the only change being that
the position of such stations has been moved 1,000 kilocycles higher in the spectrum.
This arrangement permits the same receiver to be used for the two services. The
three educational institutions now authorized to use amplitude modulation in the
non-commercial band can continue to do so, but the Commission hopes that subsequent
applicants for non-commercial educational broadcast facilities will find it economic
and otherwise preferable to utilize f-m.
How Frequencies Were Reallocated
Readjustment of the ultra-high radio frequencies to provide the 40 f-m channels
between 40,000 and 50,000 kilocycles, as well as seven channels below 108,000 kilocycles
for television service, is pursuant to allocations contained in Commission Order
The solution to finding space in the crowded radio spectrum for the needs of
these two services was achieved with the cooperation of the Interdepartment Radio
Advisory Committee in Shifting Government frequencies. This committee, representing
13 Federal agencies, advises the President in allocating radio channels for Government
The arrangement gives private services priority rights between 60,000 and 66,000
kilocycles and between 118,000 and 119,000 kilocycles in exchange for relinquishment
to the Government of the bands 41,000 to 42,000 kilocycles and 132,000 to 140,000
In addition, the Commission discontinued television service in the present television
channels Nos. 1 and 8 (44,000-50,000 kilocycles and 156,000-162,000 kilocycles respectively).
Accordingly, old television channel No.2 will be renumbered television Channel No.1;
and a new television channel No.2 will be assigned from 60,000 to 66,000 kilocycles.
Former television channel No. 8 (156,000-162,000 kilocycles), together with frequencies
between 116,000 and 119,000 kilocycles, will be used to replace the assignments
in the band 132,000 to 140,000 kilocycles. There is no change in the other eleven
channels comprising the 162,000 to 300,000 television band.
Unlimited Operation May Be Authorized After January First
The new allocations become effective immediately on a limited basis. After January
1, unlimited operation may be authorized. Regular commercial service employing wide-band
f-m, which may include the multiplexing of facsimile transmission simultaneously
with aural broadcasting, will use the 43,000 to 50,000 kilocycle band, and non-commercial
educational broadcasting stations are given the new frequencies 42,100, 42,300,
42,500, 42,700 and 42,900 kilocycles. This provides a continuous band for f-m, thus
assuring a degree of uniformity in the quality of the different frequency modulation
channels and tending toward simplicity and economy of f-m receiving sets.
The rearrangement permits the Commission to maintain seven television channels
below 108,000 kilocycles and at the same time provide an adequate number of channels
for frequency modulation. It expects these and other services to benefit by the
It points out that sky wave interference on frequencies immediately below 50,000
kilocycles is greater than on the higher frequencies. While it likewise recognizes
that shadows and fading become more pronounced as the frequency increases, it nevertheless
believes that such factors are not substantially different on frequencies in the
vicinity of 60,000 kilocycles. Furthermore, it is generally conceded that the problem
of diathermy interference is now most acute on frequencies immediately below 50,000
Thus, by allocating 60,000 to 66,000 kilocycles instead of 44,000 to 50,000 kilocycles
to the television service, a good balance has been achieved between the effects
of sky wave and diathermy interference on the lower frequencies and the effects
of shadows and fading on the higher bands.
The miscellaneous radio services now assigned frequencies between 132,000 and
140,000 kilocycles will benefit by the changes in that 9,000 kilocycles are now
allocated where formerly only 8,000 kilocycles were available. This can provide
70 channels as compared with 57 channels in the past. The change has the further
advantage of providing two large blocks of frequencies for experimentation with
different propagation characteristics.
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