June 1958 Radio-Electronics
[Table of Contents]
Wax nostalgic about and learn from the history of early electronics.
See articles from Radio-Electronics,
published 1930-1988. All copyrights hereby acknowledged.
That Hugo Gernsback was a
profound and prolific visionary is obvious by anybody's estimation. Throughout the
early and middle 20th century, the man both predicted and participated in as many
technical creations as any of his contemporaries. Being a publisher of both science
fiction and science fact books and magazines, Gernsback wrote of fantastic inventions
ranging from weapons to medical equipment to space travel (and the vehicles that
would shuttle mankind about in his quests). Just as Arthur C. Clarke's talents
extended beyond sci-fi adventures to include devising a scheme for
geosynchronous orbit satellite communications, Hugo Gernsback
designed and sold many electronics experimenters' kits, instruments, components,
and even proposed a method for determining the rotational period of cloud-covered
Venus. Because of Venus' perpetual atmospheric shroud of sulfuric acid which is
impenetrable by visible light, radar is needed to map the planet's surface and determine
when a full rotation has occurred. Gernsback describes his method here, which he
first proposed in February 1927.
Radio Signals to Venus
... Radio to the Planets Is Now Assured ...
The idea of bouncing radio signals from
heavenly bodies is not new. It originated with the writer in an article entitled
"Can We Radio the Planets?" in the February, 1927, issue of Radio News. It was then
proposed to send a radio signal from the earth to the moon and back via short waves.
The calculated elapsed time of the signal transit was 2.5 seconds to cover the two-way
distance - twice 238,854 miles, or 477,708 miles, to and from the moon. Nineteen
years later, on Jan. 10, 1946, Lt. Col. John H. DeWitt and associated scientists
of the US Signal Corps first established actual radio contact with the moon. The
elapsed time was 2.4 seconds. Our original predicted time was 2.5 seconds, an error
of 0.1 second. In the article mentioned, we also spoke of signaling Mars and Venus,
but refrained from giving elapsed signal time, because of the extreme complexity
of the problem. In 1927, we had little practical knowledge of the penetration of
short waves beyond the earth's atmosphere and into space, as well as eventual reflection
of the returning high-frequency waves on the Heaviside layer.
It is gratifying to note that in the fall of 1959 man will at last attempt to
signal the planets - Venus and Mars, not as a stunt but for serious astronomic and
scientific purposes. British radio astronomers, using the world's largest radio
telescope at the Jodrell Bank radio observatory, intend to radio-contact Venus first.
The scientists state that they will have a power output 3,000 times greater than
the average military or air field radar installation! Many new and important facts
will be learned from such a series of experiments in bouncing signals off Venus.
One will be the rotation of Venus on its axis, not known now. Our closest sister
planet is constantly shrouded in dense clouds. Hence man has so far not seen the
surface of Venus. Its rotation period is thought to be 20 to 30 days - a guess at
best. Radio astronomy via reflected signals may give us a clue to Venus' exact time
Let us now consider how the scientists will "shoot" Venus at its inferior conjunction
in the fall of 1959, when Venus will approach within 30,000,000 miles of the earth.
(The closest approach was 26 million miles on Jan. 28, 1958.) At the speed of 186,000
miles a second, the radio signal will take 5.36 minutes to cover the distance out
and back between the two planets (2.68 minutes to go to Venus, 2.68 minutes to return).
The inherent difficulty with the present-day state of the art of radio is our
inability to concentrate a beam of radio-frequency signals - the diffusion is too
great. The same is true of light. With the tremendous distances with which we have
to work, the beam spreads. It is as if we aimed a high-pressure stream of water
at a distant large football. Most of the water will not hit the object. A large
part of that which hits will splash and reflect at different angles and only a comparatively
minute amount will come back in the direction of the nozzle.
It is for this reason that the British scientists must use a large power output
if they hope to get back an intelligible radio echo signal from Venus.
The Jodrell Observatory radio telescope, the largest known in the world today,
has a great advantage in making these experiments. On account of its large size,
it can concentrate the transmitter power output into a narrower beam and, again
due to its large size, it concentrates the weak echo of the returned signal more
If in the future it should become possible to concentrate and narrow the radio
beam further, much less power would be required to contact the various planets.
Obviously, the greater the distance between earth and the outlying planets, the
more difficult the problem of bouncing back signals.
It can be seen from the above that as earth and Venus pull apart, the distance
between them increases rapidly, until at maximum separation - at superior conjunction
- the distance is 161 million miles. Here it would take the round-trip signal 28.8
minutes to bridge the space. But now the sun would become an obstacle, partly blocking
the path of the signal.
Would the signal be absorbed by the sun? Yes. Another interesting and perhaps
far-reaching test would be the effect of the sun's gravitational attraction on the
returning radio echo. This is known as the Einstein shift. If, before or after superior
conjunction of Venus, we send a signal to Venus in such a manner that the return
signal comes close to the sun, the signal should be bent toward the sun. The Einstein
shift has been confirmed with light rays, but not with radio waves up to now. This,
however, at the present time can only remain a theoretical consideration. The experiment
could not possibly be conducted with present radio frequencies unless we had a radio-astronomical
bowl transmitting and receiving antenna at least 60 miles in diameter!
In the future when we can produce super high frequencies of the electron optical
variety, which approach the frequency of light, it will be possible to record the
Einstein shift electronically.
There will not be very much practical difference when we try to signal Mars,
because the distances between our two planets are not too great at nearest approach
- about 35 million miles for Mars, 26 million for Venus. We can therefore look forward
to an early radio contact with Mars, too.
What about the further outlying planets? Possible, but increasingly difficult
the further out we go. To bounce a radio signal off Jupiter will take 1 hour and
10 minutes for the two-way transit; 2 hour 22 seconds for Saturn; 12 hours, 50 minutes
for Pluto. To hit squarely such a distant planet, say Neptune, 2,677 million miles
away at its closest is in itself a difficult feat; for the signal to return earth
without missing it altogether would be an achievement of a high order - at least
at the present state of the art. -H.G.
Posted November 17, 2020(original 6/8/2014)