Nationwide commercial television broadcasting companies wasted no
time stringing coaxial cable and microwave towers from sea to shining
sea once the NTSC format standard was adopted and manufacturers
had spooled up production after World War II. Adoption of cable
services was slow because a fee was involved, but once purely cable
channels started being added the perceived value increase convinced
consumers to open their wallets. Eventually cable eclipsed over-the-air
broadcasts for all but extremely rural areas that were not serviced
by cable. Along came satellite TV to take care of filling that void.
Once a small, inexpensive, unobtrusive Ka-band antenna replaced
the huge S-band backyard parabolic dishes and subscription prices
dropped significantly, suburbanites and city dwellers picked it
up. Soon, cable companies were feeling the pinch as their customer
bases shrunk. Not ones to sit and take the loss, 'cable' exploited
the rapidly falling landline subscriber base due to cellular service
by pushing VoIP via cable to the point where in some areas you cannot
even get legacy twisted pair telephone service. A recent
news headline reports that satellite TV subscribers are switching
to Internet streaming even though not all the same content is available
on the Web, which has caused a troubling scenario for satellite
Networks for Television
By Jordan McQuay
The technical status and future of video networks for inter-city
programming of multiple stations.
Fig. 1 - Cross-section of 8-conductor cable used
for transcontinental installation currently under construction by
The horizon represents a strong challenge to the television broadcasting
industry, because it localizes every television station. The extremely
high operating frequencies of a sight-and-sound transmitter are
effectively lost when they pass the horizon, thus limiting the area
of a station's usefulness and contributing to its remoteness.
To send televised programs to other cities or distant geographical
regions or, conversely, to obtain programs originated elsewhere,
some sort of inter-city network is required to pierce the restricting
horizon and link together any number of widely separated local television
An even stronger reason for such multiple-station programming
is the matter of economics.
Television broadcasting is a costly enterprise. It requires considerable
financial backing, from both the technical and program standpoints.
While the purchase of technical equipment is recognized as a tangible
investment in material, the high cost of operating and programming
a television station is both alarming in magnitude and intangible
The principal factor in the present retarded growth of television
broadcasting is not a shortage of equipment, but a general unwillingness
of the industry to spend large sums of money for good television
When a single production of perhaps an hour requires from 60
to 80 people - actors, actresses, set designers, carpenters, electricians,
prop men, grip men, cameramen, sound men, video operators, control
monitors, directors, producers, etc. - with rehearsals consuming
from 6 to 20 hours or more, some idea of the cost can be estimated.
But more particularly, this televised program is available only
to a local audience - perhaps only a few thousand sets. So great
is the cost of producing large-scale or lavish programs - lengthy
plays and musicals, requiring many changes of settings, props, lights,
etc. - that few existing television stations can afford to stage
and photograph good entertainment for such a restricted number of
listener-viewers. And good entertainment is defined as that on a
quality scale comparable to theater motion pictures.
This comparison with the cinema art is important, because television
must compare favorably with theater motion pictures, if television
is to succeed as both an art and an industry.
Television is also in need of a mass audience, so that commercial
advertisers will take an interest in the medium.
The only method of lowering the enormous cost of individual programs
produced for a local or limited audience is the syndication of such
programs, as in radio broadcasting, by means of multiple-station
distribution networks. Also, this is the only method of reaching
and developing a mass audience, for commercial purposes. To prevent
duplication of local service, such television networks must be inter-city,
as well as inter-regional.
Thus, the economic factor of television broadcasting is closely
integrated with the technical aspects of the new industry.
Confronted with this urgent need of the television industry,
practically all of the larger, technical communications corporations,
as well as equipment manufacturers, have responded with extensive
research and development toward systems of network-linkage for television
There are three principal methods of multiple-station programming
for television, and each is a billion-dollar enterprise in itself.
The three basic systems to be considered are: 1. Coaxial cable (multi-service
type); 2. Radio relay (microwave); 3. Film (prepared for television
The first two systems have not been developed entirely for the
exclusive use of television, since it is intended for both coaxial
cable and microwave radio links to also transmit carrier telephony,
telegraphy, telephoto, tele-printer, ticker and high-speed business
machine signals, facsimile signals, and other services.
Fig. 2 - Map shows existing and proposed routes
of coaxial cables.
Although not a network in the physical sense, film of the motion-picture
type but prepared exclusively and especially for television is included
in this analysis, because of its inevitable use as an economical
substitute (for the first two systems mentioned) during the next
decade of television - and, perhaps, the next decade after that!
All of the three systems are as yet in various stages of experimental
testing or initial construction. An important time element - of
from 6 months to 1 year - permits more careful consideration of
each system by the television industry prior to the adoption of
one or more. And the cost of each service is a significant factor
in this competition.
Of the three network 'systems, only one, coaxial cable, is now
in use as a limited regional network on the East Coast.
The idea of wire or cable transmission of a wide band of frequencies
is not new, since a workable system was developed and put in operation
by the Bell System over ten years ago to provide limited television
program service between New York and Philadelphia. The wide-band
system of transmission proved feasible, not only for occasional
television programs but, more particularly, for handling a large
number of carrier telephone channels continuously and simultaneously.
An energetic research and development program was then put into
effect by the Bell System, eventually resulting in the highly efficient
coaxial cable system of the present day.
Fig. 3 - One of the seven relay stations in the
new microwave system connecting Boston and New York, located atop
Jackie Jones Mountain near Haverstraw, N. Y. A pair of shielded
lens antennas provides two-way transmission with 1-watt beamed waves
at 4000 mc. Developed by Bell Laboratories, the radio relay system
provides wide-band communications link for television.
A section of this transmission cable (Fig. 1) actually contains
eight independent concentric cables - together with 49 paper insulated
wires for testing and maintenance purposes. The insulating discs,
separating outer and inner conductors of each cable, are constructed
of low-loss polyethylene and spaced about one inch apart. A long
section of a cable - with repeaters or boosting amplifiers, and
other gear - has a bandwidth of approximately 2.8 megacycles, which
is adequate for most monochrome video signals. Impedance is about
75 ohms at the higher frequencies of operation.
The complete cable is buried directly underground by enormous,
mobile, cable-laying apparatus (Fig. 5), which plows a suitable
burying trench, deposits the cable in place (Fig. 7), and then covers
the excavation, in a continuous operation.
Originally scheduled for only 6000 miles in 1944, the Bell System's
present cable construction program now calls for 12,000 route miles
of this broad-band facility to be in service by the end of 1950.
The map (Fig. 2) shows the cable network now in place or now under
construction (all solid lines) and extensions to be completed within
the next three years (dotted lines). These installations, it should
be noted, follow the major telephone traffic routes of the country.
Two complete coaxial cables have been installed between Washington
and New York, which is the heaviest telephone traffic route in the
Repeaters for the coaxial cable system are built around a small,
high-gain video amplifier tube, somewhat similar to the type 6AK5.
The wideband amplifier consists of three stages with feedback, giving
an over-all gain of 50 db. at the high frequencies of operation.
Each amplifier is adjusted to provide just sufficient gain to equal
the loss in a fixed equalizer - plus the natural loss of the cable.
Each stage is equipped with parallel tubes, so that if one tube
in any stage fails to function, operation of the amplifier will
not be affected. A repeater (amplifier) is inserted in a coaxial
line about every 6 or 8 miles.
Fig. 4 - Parabolic reflector antennas in use
with two-way experimental radio relay system for television.
The 8-conductor cable (Fig. 1) normally provides 480 carrier
telephone circuits simultaneously,. using r.f. modulation with crystal
control. This is the primary purpose for which the coaxial cable
was designed and developed; to increase the number of available
long distance telephone circuits, and not, as many suppose, for
carrying television programs.
Two normal channels are combined, by means of suitable terminal
equipment, to provide for transmission of high-quality audio programs,
as required for radio network distribution (for later broadcasting).
The cable thus provides audio program channels of greater frequency
bandwidth than that needed for ordinary telephone conversations.
Telegraph transmission by coaxial cable requires much narrower
frequency bands than those normally used for long distance telephony,
and suitable terminal equipment divides a single channel into either
12 or 18 separate telegraph transmission channels.
Use of the coaxial cable for video or television signals, however,
requires the entire usable frequency bandwidth, about 2.8 megacycles,
of all channels of the cable system. Thus, transmission of a single
television program over any given section of coaxial cable prevents
the use of that cable section for any other of the multiple services
(telephone, telegraph, facsimile, etc.) which it is otherwise capable
Since development began, experimental television transmission
over the inter-city coaxial cables between Washington and New York
was furnished free to television broadcasters. Now, however, these
facilities are available only on a commercial basis! Recent publications
of the tariffs created a near-panic in the television industry.
The charges averaged better than $40 per circuit mile of cable linking
New York, Philadelphia, Baltimore, and Washington. The rate of inter-city
movement of television programs now costs almost ten times the rate
to send audio network programs (for later broadcast) between the
same cities. Higher rate for television facilities is justified,
however, by the technical difficulties involved in handling video
signals and the limited number of cable conductors between cities
which must be shared with telephone, telegraph, and other services.
But from the operational standpoint, this high cost probably will
prevent many television stations from accepting programs originating
in other cities. For example: A television station in Washington
would pay a minimum of $9500 monthly for video program service from
New York, and vice versa.
Fig. 5 - A giant cable plow used for laying coaxial
cable is shown in operation. Line runs from Baltimore to Washington.
While the effective bandwidth of this coaxial cable system is
entirely adequate for most television work, it places a pronounced
limitation on the degree of picture fidelity. For the transmission
of chromatic television, requiring a bandwidth of at least 6 megacycles,
the coaxial cable is useless.
Nevertheless, limited facilities for inter-city distribution
of television programs are now in existence (Fig. 2) and extensive
facilities for national network coverage will be available within
a few years - at a price. However, considering the economic factor,
it's extremely doubtful that the demands of television will ever
become so strong financially as to force the Telephone Company to
lease any sizable proportion of its coaxial cable facilities, because
these facilities will yield higher revenue when used for other communications
Seeking to avoid excessive cable tolls, some television broadcasters
and manufacturers have turned hopefully to fixed, point-to-point,
microwave radio relay systems.
The development of microwave techniques for selective communication
makes these tiny radio waves ideally suited for highly directional,
overland point-to-point transmission of video signals. Because of
the nature of these waves, low-power but stable radiation is possible
at operating frequencies of thousands of megacycles with virtual
elimination of noise and other interference.
The portion of the frequency spectrum between 1 meter and 1 centimeter
is relatively unused by other radio services. In that range there
is instantly available nearly 10,000 channels (3-mc. wide) for transmission
of monochrome television, or nearly 5000 channels (6 mc. wide) for
radio-relay transmission of chromatic (color) television programs.
These figures can be amplified to almost any number, since distance
limitations permit many stations to operate on the same channel
frequency within relatively small distances of each other.
Much of the effectiveness of a microwave radio-relay system is
due to the characteristics of such waves. Microwaves are extremely
short in length, and behave much in the manner of light waves. Radiated
energy from a microwave transmitter can be concentrated toward a
distant receiving point by means of a highly directional antenna.
At the receiving point, such radiations are "collected" by another,
similar antenna. Microwaves, like light waves, travel in straight
lines and do not follow the curvature of the earth, thus the receiving
point must be within view of the transmitter. Such a group, of transmitter
and distant receiver, is known as one link of a relay system.
By feeding the output of the receiver to another transmitter
and its antenna, at the receiving site but facing oppositely, the
microwave signal is reradiated and can then be picked up by another,
distant receiver. In this manner, by arranging successive links
in tandem, the microwave beam of concentrated energy can be relayed
to any desired, distant point of reception. The process is practically
instantaneous; almost at the speed of light.
Although the distance range of a single link is limited to the
line-of-sight or optical distance between transmitter and receiver,
two or three frequency assignments can be used and reused by successive
links of the system.
The microwave beam is modulated by the wide-band or video signal,
and the factor of bandwidth is just as important as for the coaxial
cable. Two-way operation of a relay system over the same path requires
a double beam, one directed oppositely to the other. Thus, a single
relay point is equipped with two directional antennas for each of
the two links of the relay circuit; one for transmission of one
beam, one for reception of the other beam. For centimeter operation,
these usually consist of parabolic reflectors (Fig. 4) or horn or
lens antennas (Fig. 3).
A microwave radio relay system has several advantages over coaxial
cable for television networks. Very little time is required to locate
or relocate towers or other antenna structures. Difficulties of
construction over water, deserts, rocky regions, and mountains are
greatly reduced. When all links of the relay system are adjusted
and functioning properly, the general quality of video transmission
is much improved. All maintenance is concentrated at the antenna
towers or buildings, instead of being distributed along the length
of a cable buried underground.
Main disadvantage of microwave radio relay systems is their inherent
ability to generate and amplify noise and similar interference.
Improved circuit design of amplifiers is likely to overcome this
important objection. While operational and maintenance costs are
low, the initial cost of this equipment is considerable, since a
great many relay points are required to link cities separated by
an appreciable distance.
Fig. 6 -A. T. & T.'s radio relay system operating
between New York and Boston.
Relay towers are generally constructed as high as is compatible
with structural safety, and the transmitting and receiving antennas
are mounted somewhere near the tops of the towers. Equipment at
all relay points is standardized, and individual stations operate
unattended. Maintenance personnel is stationed at main terminal
points, equipped with precision, fault-finding apparatus.
Cost of constructing a microwave radio relay system of any appreciable
circuit length (over 50 miles) is considerable, and increases with
distance at a greater rate than coaxial cable facilities.
Again, the operational cost figures heavily against television.
Because of the expense of such installations, it is far more profitable
for the microwave relay system to be used by the other communications
services, telephone, telegraph, wirephoto, etc., who are prepared
to pay high rates for use of the facilities. Resultant revenue would
be far in excess of that obtained from a single television or video
service over the same system.
After five years of extensive experience in the operation of
a commercial radio relay system between Philadelphia and New York,
RCA has developed a 1-centimeter radio relay system for Western
Union, having a bandwidth (received) of 4 megacycles occupied by
32 channels for carrier telephone, telegraph, facsimile, and similar
services. There is no provision for television service in the Western
Unless a radio relay system is owned and operated, or its operations
directly controlled, by individuals or corporations within the television
industry, it is unlikely that television programs will be transmitted
by such a system, because of the economic factors involved.
Philco, Raytheon, and a few other radio manufacturers have inaugurated
extensive programs covering research and development of new microwave
radio relay systems. But detailed data on their technical accomplishments,
if any have been made, are not available.
Fig. 7 - Coaxial cable on reel (at right) is
guided into cable plow (left) and buried in earth, as plow is drawn
Effectively competing with itself in at least one aspect - coaxial
cable - the Bell System has also entered into active development
of microwave radio relay equipment with some very promising results.
Construction work begun a year ago on a Boston-New York relay circuit
(Fig. 6) has just been completed. The system consists of two main
terminals, and seven relay stations. One of them is shown in Fig.
3. Average distance between relay points is about 27 miles; distance
of the total circuit is about 230 miles. The system operates with
a frequency in the vicinity of 4000 megacycles, using two channels
in each direction of transmission. A usable frequency bandwidth
of almost 4 megacycles is available for television service, but
all channels are to be used normally for carrier telephone operation.
At each relay point, radiation and reception is accomplished by
electromagnetic horns (Fig. 3) with 10x10 foot apertures, and equipped
with a metal lens to focus the microwaves into a highly directional
A similar radio relay circuit between New York and Chicago will
soon be under construction, also by the Bell System, requiring more
than 40 relay points between terminal stations. Three years will
be needed to complete the work, at an estimated cost of seven million
One other type of radio relay system called "Stratovision" is
worthy of mention, only because of its unique nature and purely
theoretical possibilities. This system of television broadcasting
- from a specially equipped, high-altitude plane in flight over
a service area - was publicized widely a few years ago. But despite
a few tests made under ideal conditions, the system has yet to be
Video programs originating on earth are transmitted - via microwaves
- to a stratoliner, flying above an area in continuous circles at
an altitude of about six miles. There the television signals are
received, and then broadcast toward the earth with a more-or-less
conventional television transmitter. In this way, limiting effects
of the horizon are overcome and, theoretically at least, a vast
area on earth could receive the radiated programs. The originator
(Westinghouse) claims that 78 percent of the population from coast-to-coast
would be able to receive guaranteed, (sic) clear reception and sharp
images. Main difficulty with this theory of operation, is that airplanes
characteristically deflect television signals causing momentary
interference and, occasionally, ghost images at the point of reception.
Exhaustive tests are said to have been made during the past year,
but no results have been published or made available to the public.
Quite apart from the economic limitations and any technical
inefficacies of the types of network systems previously described,
there is an important element of availability of these systems,
which should certainly be considered.
Even after completion of the proposed coaxial cable network,
it may be of no practical use for television if the industry is
expected to lease sections of the cable at a price in proportion
to the number of channels required for transmission. With a swing
to higher definition or, eventually, to chromatic pictures, in either
event the coaxial cable will be obsolete.
Most potential hope for television networks are microwave radio
relay systems, if they are owned and operated by those within the
television industry. However, it will take many years to construct
sufficient beam circuits to reach all centers of large population.
Television is in need of a mass audience today! And unless a
definite audience is assured, advertisers will not spend money for
television programs-a station's only source of revenue.
Solution of the immediate problem of a television network is
film. Not ordinary theater motion-picture film, but motion-picture-type
film - made for, and used by, television broadcasting stations only.
Though not strictly a "physical" television network, the use of
television film is the most practical and immediate means of inter-city
Film could be produced much more economically than the installation
costs of coaxial cable or radio relay equipment. Film would be equal
to, or a considerable improvement over, a "live" presentation of
the same program, because the television film could be edited just
as motion-picture or theater film. Since the film is exclusively
for video reproduction, all aspects of its production are specifically
designed for television's small screen and gray shading.
Only film guarantees adequate lighting of scenes, flawless dialogue,
absolute focus, and repeat performances of uniform quality. Time-zone
differences-such as exist between New York and California - would
be unimportant if the video program was on film.
The technical aspects of film production more correctly belong
in the category of motion pictures, since only the lighting, directing,
and general philosophy are changed when making films exclusively
for television. For this reason, technical data on film production
is not included in this system's analysis.
Film size most likely to be used for television will be 16 mm,
which is more practical and economical than larger motion-picture
theater film. The speed of television film, 30 frames per second,
requires special projection equipment, but general operation is
identical to theater technique. Operating costs of a film "network"
Entertainment, not spontaneity, is an important factor in television
program appeal. And from the economic standpoint, as shown, the
cost is very low. Until suitable coaxial cable or radio relay network
systems are established, requiring at least a decade for national
coverage, the logical and economical method of multiple-station
television programming is by means of film.
Posted August 21, 2015