[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Craft,
published 1929 - 1953. All copyrights are hereby acknowledged.
When this story was published in
1938 in Radio−Craft magazine, India was a country of roughly 2 million
square miles, while the 48 United States had about 3.1 million square miles. Radio
station growth in the U.S. already had a three-decade head start in establishing a nationwide
network of broadcast and receiving stations. Manufacturing of the required equipment
was well established within our borders. India, by contrast, relied heavily on outside
sources for equipment and the training of operators and servicemen. The U.S. never
has had and still does not have an official "state radio" as was All−India Radio.
A nice feature of the system was inclusion of a time-keeping signal that would allow
anyone within the reception of a clear signal to synchronize clocks. The included
map shows where the first four 10 kW main shortwave transmitters were installed
in key population areas. The terms "direct−ray" and "indirect-ray" were used at
the time to describe non−skip and atmospheric skip, respectively, propagation.
India's New Network of Radio Broadcasting
Fig. A - Reproduction of the cover painting showing the
8,000-V. Philips rectifier tube to be used in the new All-India Radio Broadcasting
A new radio system, with broadcast band and short-wave transmitters and time
clock operated, pre-tuned receivers in key villages, furthers India's plan for eventual
complete coverage. An unusual feature of this new All-India Radio system is that
the pre-tuned receivers are dial-less and padlocked; and that the 8,000-volt power-supply
tubes use mica "lampshades" to reduce possibility of "backfire."
The technical problem that now confronts the Broadcasting Department of the Government
of India, All-India Radio, is that of providing a service over an area of nearly
2,000,000 square miles with the limited funds available, official announcements
In the development of broadcasting in India it has been accepted by All-India
Radio as a fundamental precept that a satisfactory broadcasting system must provide
a measure of service to the whole country. This immediately determines the principle
of operating transmitting stations on the short wave-lengths. At the same time,
it is admitted that this is not a final solution. Simultaneously with the provision
of a short-wave or "second-grade" service to the whole area, a medium-wave or "first-grade"
service is necessary for the large towns. The basic principle of broadcasting development
in India, therefore, is to provide a short-wave service to the whole country and
to support this by a continual expansion of the area served by medium-wave stations
as funds become available.
10 Transmitters Ordered
Fig. B - View of some of the power supply equipment for
the transmitters. At the right is the bank of four 8,000 V. Philips rectifier tubes.
To this end 10 transmitters have been ordered. Four short-wave "key" stations
will be established at Delhi, Bombay, Calcutta, and Madras, and will be of 10-kw.
(aerial) power. A second short-wave transmitter of 5-kw. power is also to be provided
at Delhi for special purposes. The development program does not envisage any future
increase in the number of short-wave stations. These short-wave stations will provide
a "second-grade" service to the whole of India.
At the same time, 5 medium-wave stations have been ordered, and will be situated
at Lahore, Lucknow, Trichinopoly, Dacca, and Madras, the first 4 stations having
a power of 5 kw. The Madras medium-wave station will have a power of 250 watts,
and will service the city only, as Madras will also be provided with a 10-kw. short-wave
transmitter. With these stations, and the existing medium-wave stations at Delhi,
Bombay, Calcutta, and Peshawar, All-India Radio will have in operation 5 short-wave
stations and 9 medium-wave stations. Two of the new stations are expected to be
in operation by the end of the year: the 10-kw. short-wave station at Delhi and
the 5-kw. medium-wave station at Lahore.
Choice of Short Wavelengths
It is expected that the Indian short-wave stations will normally operate in the
daytime on the 30-meter and 49-meter bands and at night principally on the new 60-meter
and 90-meter bands for broadcasting which will be proposed at the forthcoming Cairo
It is considered that there should be no interference between the Indian short-wave
stations operating an internal service and the European and the other short-wave
stations operating an international service, as the Indian day wavelengths are the
European night wavelengths, and the Indian night wavelengths are not used by the
broadcasting stations operating an international service.
Fig. C - The map of India showing the locations of both
the existing and the contemplated short-wave and medium-wave broadcasting stations.
Only strategic spots, from the good-reception angle, were chosen.
Fig. D - Impressive view of the short-wave transmitters
to be used in the new All-India Radio broadcasting system. Other transmitters will
operate in the medium-wave band, thus providing day and night broadcasting.
Direct and Indirect "Ray" Service
The distinction which has previously been drawn between the use of medium wavelengths
and short wavelengths for broadcasting in India is based on the principle that the
technically "perfect" broadcasting service can be given only by use of the "direct
ray". The range of the direct ray on the medium-wavelengths is, however, small,
especially in India, where severe atmospherics are present for large periods of
the year. In actual fact the area which will be covered by a first-grade direct-ray
service when all the medium-wave stations envisaged in the development program are
in operation will be approximately 2% of the total area of India. The fundamental
importance of the short-wave, indirect-ray service is therefore very evident.
It may be asked why indirect-ray transmission is not satisfactory on the medium
waves. In Europe good long-distance, indirect-ray reception is sometimes obtained,
but this is possible only because of the relative absence of atmospheric disturbances.
These depend upon wavelength and their strength is, in general. proportional to
wavelength: the shorter the wavelength, the less the atmospheric disturbance. It
is desirable, therefore, to choose as short a wavelength as possible to avoid atmospheric
disturbances, and this is limited only by the intervention of the phenomenon of
Sets for Village are padlocked!
An unusual requirement in receiving-sets for India which deserves special mention
is provided for by the special receivers that have been developed by the Research
Department of All-India Radio for community reception in Indian villages. These
receivers are mounted in metal cases and padlocked. No controls appear outside service.
the box. The receiver is left tuned to the local station. A clockwork time-switch
mounted in the box turns the set on and off at the correct time for the "Village
Hour". The only attention required is a visit once every 3 weeks, when the car-type
storage battery which operates the receiver is changed and the clock rewound.
Village-receiver schemes are now in operation in the service areas of each :
of the existing medium-wave stations, and a number of new projects will come into
existence as soon as the new stations are in operation. (The foregoing material
was supplied by Radio Press Service. Paris, France)
The 8,000-V. Rectifiers
Fig. 1(B) - fundamental circuit of the Philips' 8,000-volt rectifier.
Fig. 1 - At (A) pictorial view of Philips' 8,000-volt rectifier.
The new rectifier, which constitutes such a major contribution to the efficiency
and effectiveness of the All-India Radio system, is the cover subject for this month's
issue of Radio-Craft. This tube has a far lower internal resistance (and therefore,
higher efficiency) than the vacuum rectifiers customarily employed. This feature
also makes its cooling less of a problem.
Figure 1A is a view of the tube pictured in Fig. A and on the cover and
shows the essential elements. A schematic representation of the tube, and the means
by which the rectifier can be controlled and regulated without making or breaking
any mechanical contacts in the high tension circuit, are shown in Fig. 1B.
One weakness of the tube was its liability to "backfire" under certain conditions,
when the glow-discharge arcs over. This is remedied by placing the anode and cathode
in separate chambers, with a third chamber between them. The mica "lampshade" above
the tube keeps the upper chamber warm and prevents the condensation or mercury vapor
at the anode which, incidentally, is made of graphite, a material which has low
Posted November 17, 2023
(updated from original post on 2/20/2017)