Post on 24-Apr-2018
Radio JOVE Project at
Western State College
byAlan Piquette
Colorado Space Grant SymposiumApril 6, 2002
SubmittedMarch 22, 2002
RADIO JOVE PROJECT AT WESTERN STATE COLLEGE
Abstract
People have been studying the skies since the beginning of humanity, but until the 20th
Century all they could observe was the part of the universe that emitted visible radiation. Few
suspected that, beyond their range of vision, a richer and more complete cosmos was waiting to
be discovered. This paper discusses radio astronomy as a means to broaden our perspective of
the universe in which we live. The Radio JOVE Project is an educational outreach effort of
NASA, the University of Florida, and others, whose purpose is to educate people about planetary
and solar radio astronomy, space physics, and the scientific method by providing teachers and
students with a hands-on radio astronomy exercise. The specific scientific goal is to monitor
20.1 MHz radio emissions from Jupiter and the Sun using the Radio JOVE Project antenna and
receiver. The data collected by observers all over the Earth are sent to a central location for
analysis and comparison. The JOVE receiver kit and antenna can be assembled by anyone with
a moderate background in electronics and some soldering experience. The receiver put together
for this project required approximately 16 hours of construction time. Testing is now in progress
and data collection will hopefully soon follow.
Introduction
A Brief History of Radio and Radio Astronomy: Most people know that astronomy is
the study of the universe and the objects in it. When many of them hear the word astronomy,
however, they automatically assume that a form of optical science is being discussed. In other
words, images of telescopes and eyepieces come to mind, but the study of the cosmos is not
limited to visual means alone. While the visible sky contains all the familiar constellations and
the faint glow of our own Milky Way galaxy, there is another window to the universe open to
anyone with the proper equipment. This window can be thought of as the "radio sky," which is
filled with radio sources that only rarely match the positions of visible stars (Thurber, 1995).
The branch of science that deals with the detection and study of those sources is radio
astronomy.
Similarly when people consider of the word radio, they usually think of sound. While
everyday experience and Hollywood movies make people think of sounds when they see the
words radio waves, radio astronomers do not actually listen to noises. First, sound and radio
waves are different phenomena. Sound consists of pressure variations in matter, such as air or
water (Lea & Burke, 1997). Sound will not travel through a vacuum. Radio waves, like visible
light, infrared, ultraviolet, X-rays, and gamma rays, are electromagnetic waves that do travel
through a vacuum. When you turn on a radio you hear sounds because the transmitter at the
radio station has changed the characteristics of the radio waves to make them carry information
about the sound of voices and music. An AM/FM radio receives the radio waves, deciphers this
information and changes it back into audible sounds.
Following Guglielmo Marconi's successful transatlantic communications in 1901,
commercial use of radio mushroomed (Bracher, 2000). Ships were equipped with radio, huge
commercial stations were set up to handle intercontinental messages, and many other uses were
found for the new technology. In those days, it was thought that the only really useful
frequencies for long-range communication were the very low frequencies, or the very long
wavelengths (Thompson et al., 1991). Thus, when the first government regulations were
imposed on radio in 1912, the amateur operators (hams), whose interest in radio was personal
and experimental, rather than commercial, received the use of undesirable frequencies. They
were given the use of wavelengths of 200 meters and shorter, roughly the frequencies above the
current AM broadcast band. These were generally thought useless for long-range
communication (Bracher, 2000).
The wavelength restrictions were rather loosely enforced prior to U.S. entry into World
War I in 1917, when all amateur and other non-government use of radio was shut down. When
amateur operations resumed in 1919, it was much more imperative to abide by the rules, so the
hams had to find out just what they could do with the short waves (Thurber, 1995).
Starting in 1921, amateurs made concerted, organized efforts to communicate across the
Atlantic with short waves. In December of 1921, an amateur station in Connecticut was heard
by an American amateur sent to Scotland with state-of-the-art receiving equipment (Cornell,
1981). On November 27, 1923, amateurs in the U.S. and France made the first transatlantic two-
way contacts on shortwave frequencies. In the following two months 13 European and 17
American amateur stations had made two-way transatlantic shortwave contacts (Thurber, 1995).
Within a year, amateurs had communicated between North and South America, South America
and New Zealand, North America and New Zealand, and London and New Zealand.
These accomplishments proved beyond a doubt that ionospheric refraction could enable
worldwide communication by shortwave radio (Brinks & Dahlem, 1996). Further amateur
experiments showed that, by using a variety of frequencies in the shortwave region (3-30 MHz),
long-range communication could be maintained both day and night. In addition, the shortwave
communications were accomplished with transmitters of only modest power, unlike the giant,
many-kilowatt transmitters needed for long-range communication at the lower frequencies
(Thurber, 1995).
Naturally, once the hams showed the value of shortwave radio, many commercial firms
became interested. One of these commercial interests was the telephone company, which
thought that shortwave links might be used to carry intercontinental telephone calls, saving the
expense of laying cable on the ocean floor (Thurber, 1995). However, as any ham or shortwave
listener today knows, shortwave communication is subject to much noise and static. The
telephone company sought to identify and find ways to lessen or eliminate this noise.
In the early 1930’s, a radio engineer named Karl G. Jansky tried to determine the causes
of radio communications static on transoceanic telephone connections for Bell Telephone
Laboratories (Bracher, 2000). Jansky did not locate any specific source of the static and
interference. However, he did note that as he turned his antenna toward the galactic plane of the
Milky Way, he recorded an increase in static hiss. After much testing and verification, he
concluded that the source of the interference was from the direction of the center of the Milky
Way (Thurber, 1995). Jansky's discovery did not convincingly establish the existence of radio
emissions from the sky, and the broad beam of his antenna only vaguely suggested any details of
those emissions at 20.5 MHz. As a result, his work did not appear to create much interest, and
Jansky did not immediately have the opportunity to pursue his discovery in depth (Bracher,
2000).
Then, beginning in 1937 and continuing into the 1940’s, an amateur radio operator,
Grote Reber, built a 31-foot parabolic dish antenna in his back yard to continue Jansky's work.
By observing VHF and UHF as high as 500 MHz, Reber discovered particular regions of intense
radio emissions, or static hiss. Reber then plotted regions of the sky according to the intensity of
the radio sources. He eventually published a map in 1944 of a large part of the sky based on his
work (Thurber, 1995). Jansky's and Reber's efforts are considered by many to represent the
foundations of modern radio astronomy.
Thus, the accidental discovery of cosmic radio emissions was a direct result of radio
amateurs' success in developing shortwave communications. Then, for several years after this
original discovery, the only people following up with systematic and well-designed radio
astronomy observations were radio amateurs. Today, the connection between radio astronomy
and amateur radio remains strong. Many prominent radio astronomers first became interested in
science through involvement with amateur radio in their youth (Bracher, 2000).
The Basics of Radio Astronomy: Radio astronomy is the study of distant objects in
the universe by collecting and analyzing the radio waves emitted by those objects. Just as
optical astronomers make images using the visible light emitted by celestial objects such as stars
and galaxies, radio astronomers can make “images” using the radio waves emitted by such
objects, as well as by gas, dust and very energetic particles in the space between the stars. Radio
astronomy has been a major factor in revolutionizing our concepts of the universe and how it
works. Radio observations have provided a whole new outlook on objects we already knew,
such as galaxies, while revealing exciting objects such as pulsars and quasars that had been
completely unexpected (Harwit, 1984).
One of the primary sources of cosmic radio emission is the electron. Electrons, like other
charged particles, emit photons when they lose energy. For example, an electron can lose energy
when it decelerates or changes direction. The photons carry away the energy that the electrons
have lost, just as hot brake pads carry away the energy a car loses when the driver brakes (Brinks
& Dahlem, 1996). If the electrons lose only a small amount of their energy, they emit the
weakest type of photons: radio photons.
Not all radio photons are identically emitted. Their properties depend on where the
electrons are. In neutral gases, such as air, practically all electrons are bound. They are trapped
in orbit around the nuclei of atoms or molecules. In a bound system, an electron is not free to
move at will. It is forced into one of a limited number of stable orbits, each corresponding to a
certain amount of energy. When the electron drops from one orbit to a lower orbit, the photon
that it emits carries away the difference in energy between the two orbits (Atkins, 1999).
There are several types of galactic radio emissions. The first type, discovered in 1932 by
Jansky, is spread over a wide band of radio frequencies. It is produced when free electrons are
scattered by collisions with heavier ions in the ionized interstellar gases surrounding hot, bright
stars (Thurber, 1995). A second type, synchrotron radiation, is emitted by energetic electrons as
they quickly spiral within the strong magnetic fields in the surroundings of super-nova remnants
(Brinks & Dahlem, 1996; Thurber, 1995). A third type originates in interstellar matter, which
radiates at discrete frequencies characteristic of the quantum jumps made by electrons in atoms
and molecules, such as hydrogen and helium (Thurber, 1995).
Radio waves also come from beyond the Milky Way. Some extra-galactic radio sources
are detected only by their radio emissions, while others are correlated with optically observed
galaxies and other objects. Radio sources produce either continuum radiation, which covers a
broad range of wavelengths, or line radiation that is radiated at one specific wavelength, much
like an optical spectral line (Brinks & Dahlem, 1996).
Besides localized radio sources, there is also uniform low-level cosmic radio noise
coming from every direction in the sky. That cosmic background radiation (CBR) lends support
to the theory that the universe began with an explosive big bang, rather than always having
existed in an unchanging state having an isotropic (uniform in all directions) property (Thurber,
1995).
The antennas and receivers used in present-day radio astronomy vary widely, so it is
difficult to describe a typical arrangement. However, in general, the antenna intercepts and
collects the radio signal from the celestial source. After preamplification at the feed-point, the
signal is carried by cable to the main receiver, where it is selected according to frequency and
amplified. The intercepted signal is amplified further, detected, and integrated, and the output is
displayed on an analog recorder or other device. It also can be recorded in digital form on
magnetic tape for further processing by computers (Thurber, 1995).
The radio signals arriving on Earth from astronomical objects are extremely weak,
millions (or billions) of times weaker than the signals used by communication systems. For
example, a cellular telephone located on the moon would produce a signal on earth that radio
astronomers consider quite strong (Thompson et al., 1991). Because the cosmic radio sources
are so weak, they are easily masked by man-made interference. Possibly even worse than
complete masking, weaker interfering signals can contaminate the data collected by radio
telescopes, potentially leading astronomers to erroneous interpretations (Fridman, 2000).
By international agreement, radio frequencies are divided into bands designated for
different types of uses. For example, FM radio stations all are within a certain range of
frequencies that is different from the band of frequencies in which AM stations operate (Lazio &
Nordgren, 2001). Similarly, TV stations use different frequencies than police radios. These
international frequency designations are designed to prevent one type of station from interfering
with stations of another type.
A number of frequency bands are allocated to radio astronomy. Because radio
astronomers do their work with extremely sensitive receiving equipment, transmitting is
generally prohibited in the radio astronomy bands (Thurber, 1995). However, transmitters using
frequencies near those assigned to radio astronomy can cause interference to radio telescopes.
This occurs when the transmitter's output is excessively broad, crossing over into the radio
astronomy frequencies, or when the transmitter emits frequencies outside its intended range.
Other interference arises because radio transmitters often unintentionally emit signals at
multiples of their intended frequency (Fridman, 2000).
As use of radio for devices such as cellular telephones, wireless computer networks,
garage door openers, and a whole host of other uses continues to increase, the threats to radio
astronomy from inadequately engineered transmitters increases. A prime threat comes from
transmitters in orbiting Earth satellites, since those transmitters are located overhead, precisely
where radio astronomers must aim their telescopes to study the universe. In addition, many
types of equipment not normally considered to be radio transmitters, particularly computers or
systems incorporating microprocessors, emit undesirable radio signals (Thompson et al., 1991).
Good engineering can prevent or minimize interference to radio astronomy. Spillover
from overly broad transmitters and other unintended signals do nothing to improve the
performance of a communication system. Technology readily available to radio engineers can
eliminate or drastically reduce these unwanted signals that threaten radio astronomy. It is
especially important that such interference-reducing technology be included in orbiting satellites
(Thurber, 1995). Radio astronomers do much on their own to minimize the effect of interfering
signals, from locating radio telescopes far from urban centers whenever possible to designing
their antennas and electronic equipment with features that reduce interference.
Communication between radio astronomers and other users of the radio spectrum is vital.
Engineers at radio telescope facilities often can help with suggestions for ways to minimize
interference. There are numerous examples of situations in which a radio observatory and a
transmitting facility have cooperated to implement a technical solution allowing both to achieve
their objectives (Thurber, 1995).
Importance of Radio Astronomy: The purpose of a radio astronomer is to do
fundamental research on the nature of the universe in which we live (Finley, NRAO). This
research hopes to answer some of the biggest questions we can ask, such as how did the universe
begin (if it did begin), how big is it, how old is it, and how will it end (or will it end)?
Astronomy provides the background knowledge of where we, and the planet on which we live,
fit into the universe, which suggests it is a vital part of the culture of all mankind. A person
deprived of the broad aspects of astronomical knowledge is as culturally disadvantaged as one
never exposed to history, literature, music or art (Finley, NRAO). As astronomers make known
new discoveries about the universe, they potentially enrich the lives of millions.
From the dawn of civilization, astronomy has provided important stepping stones for
human progress. Our calendar and system of time-keeping came from astronomy (Funk &
Walls, 1995). Many of today's mathematics are the result of astronomical research. Hipparchus,
a Greek astronomer, invented trigonometry. The adoption of logarithms was driven by the needs
of astronomical calculations. Sir Isaac Newton invented calculus, the basis of modern science
and engineering, primarily for astronomical calculations (Finley, NRAO). Astronomy provided
the navigational techniques that allowed sailors and aviators to explore our planet. The space
age, which brought the communication and weather satellites upon which we depend each day,
would have been impossible without the knowledge of gravity and orbits discovered in part by
astronomers (Funk & Walls, 1995). Radio astronomers led to the development of low-noise
radio receivers that made possible the satellite communications industry. Image-processing
techniques developed by astronomers now are part of the medical imaging systems that allow
non-invasive examination of internal organs (Finley, NRAO).
From revealing the remains of the Big Bang to suggesting the existence of neutron stars,
radio observers have provided science with insights unobtainable with other types of telescopes.
Of the ten astronomers who have won the Nobel Prize in Physics, six of them used radio
telescopes for the work that won them the Nobel (Thurber, 1995). Radio telescopes today are
among the most powerful tools available for astronomers studying nearly every type of object
known in the universe.
It seems that astronomy has much still to offer to human knowledge and advancement.
From the space shuttle to the transistor, from television to lasers, the developments of the 20th
Century were based on the study of matter and energy. Astronomy offers scientists a wide range
of backgrounds with a virtually infinite variety of cosmic laboratories for observing physical
phenomena (Finley, NRAO). It is not likely that any laboratory on this planet will ever produce
gravity as strong as that of a black hole, matter as dense as that of a neutron star, or temperatures
as hot as inside a supernova.
The Radio JOVE Project: The Radio JOVE Project is an educational project developed
by NASA, the University of Florida, and others, whose purpose is to educate people about
planetary and solar radio astronomy. The JOVE project provides teachers and students with a
hands-on radio astronomy exercise that demonstrates the scientific method and is a good
introduction to space physics in general (http://radiojove.gsfc.nasa.gov). The primary goal is to
monitor radio emissions from Jupiter and the Sun using the Radio JOVE Project antenna and
receiver. Since monitoring Jupiter (associated with the term Jovian) is one of the specific goals,
it is clear to see why the project title is Radio JOVE. The JOVE receiver kit and antenna can be
obtained and assembled by anyone with a moderate electronics background, which includes
some soldering experience. The receiver put together for this project required approximately 16
hours of construction time and about one hour of testing and aligning. Upon successful
completion of the antenna/receiver kits, the JOVE detection system provides a means to detect,
amplify, and record radio emissions from Jupiter and the Sun having a frequency of 20.1 MHz.
It is important to study the radio emissions of both Jupiter and the Sun to better
understand their magnetic fields and their plasma environments (http://radiojove.gsfc.nasa.gov).
Studying other planets helps us advance our understanding of Earth. Earth also emits radio
waves by a process similar to that of Jupiter, which means we can better understand this
emission process on Earth by monitoring Jupiter with all sorts of radio antennas. Not only can
we learn about why the radio waves are created and how they move through space, but we can
also learn about Jupiter’s interior and about its moons (http://radiojove.gsfc.nasa.gov). Jupiter
radiates radio waves because the planet has a magnetic field, and this magnetic field originates
deep in the interior. The overall strength of the magnetic field directly affects the type of radio
emission. Knowing this type of information assists us with the theory of how the magnetic field
is created and in determining the composition of the various interior layers. The satellite Io is
close enough to Jupiter that they interact electromagnetically with each other
(http://radiojove.gsfc.nasa.gov). It is, therefore, possible to learn more about Io and the other
Jovian satellites as well.
By monitoring the radio emissions from the Sun, it will hopefully allow us to learn more
about other stars in general. Studying the Sun, using radio astronomy, allows us to find out
more about how the Sun affects the Earth and the other planets of the Solar System.
The remainder of this paper will deal with the construction of the Radio JOVE receiver
and antenna, and how the JOVE system detects, manipulates, and displays radio emission data.
Experimental
The Radio JOVE Receiver: The Radio JOVE receiver is a short-wave receiver that
detects radio signals from the planet Jupiter and also from the Sun. The JOVE receiver contains
more than 100 electronic components such as resistors, capacitors, inductors, and integrated
circuits (IC’s) as well as some other various pieces of hardware. Thus, as one might guess,
construction of the receiver included the handling of small, delicate, electronic parts, most of
which were mounted and soldered on a printed circuit (PC) board.
Radio signals from Jupiter are rather weak. In fact, they produce less than a millionth of
a volt at the antenna terminals of the receiver. Thus, these weak radio frequency (RF) signals
must be amplified by the JOVE receiver and converted to audio signals of adequate strength to
drive headphones or a loudspeaker (Flagg, 1999). The receiver also contains and acts as a
narrow filter, which is tuned to a specific frequency so as to hear Jupiter while at the same time
blocking out strong Earth-based radio stations on other frequencies. The receiver and its
accompanying antenna are designed to operate over a narrow range of short-wave frequencies
centered on 20.1 MHz. This frequency range is optimum for hearing Jupiter signals (Flagg,
1999). Before discussing the major electrical components and what they do, it would be
beneficial to take a brief look at the overall receiver in the form of a block diagram (Figure 1 in
the appendix).
The antenna, which will be discussed in more detail in the next section, intercepts weak
electromagnetic waves, which have traveled roughly one-half billion miles from Jupiter to the
Earth (Frazier, 1985). When this electromagnetic radiation strikes the wire antenna, a small RF
voltage is created at the terminals of the antenna (Flagg, 1999). Signals from the antenna are
delivered to the receiver by a coaxial-cable transmission line.
Signals from the antenna are filtered to reject strong out-of-band interference and are
then amplified using a junction field effect transistor (JFET) (Flagg, 1999). The RF bandpass
filter and RF preamplifier perform these filtering and amplification processes. This transistor as
well as some other nearby circuitry provide additional filtering and amplify incoming signals by
a factor of approximately ten. The receiver-input circuit is designed to efficiently transfer power
from the antenna to the receiver while producing a minimum amount of noise within the receiver
itself (Flagg, 1999).
The local oscillator (LO) and mixer carryout the significant task of converting the desired
radio frequency signals to the range of audio frequencies. The LO generates a sinusoidal voltage
waveform at a frequency in the vicinity of 20.1 MHz (Flagg, 1999). The exact frequency is set
by the tuning control on the front panel. The amplified RF signal from the antenna and the LO
frequency are both fed into the mixer, which develops a new signal that is the mathematical
difference between the LO and the incoming signal frequency. An example that is used by
Flagg (1999) in the JOVE receiver instruction manual is: suppose the desired signal is at 20.101
MHz and the LO is tuned to 20.100 MHz. The difference in frequency is therefore 20.101-
20.100 = .001 MHz, which is the audio frequency of 1 kilohertz. If a signal were at 20.110
MHz, it would be converted to an audio frequency of 10kHz. Since the RF signal is converted
directly to audio, the radio is known as a direct conversion receiver (Flagg, 1999).
To get rid of interfering stations at nearby frequencies, the JOVE receiver uses a low pass
filter that is similar to a window a few kilohertz wide through which signals from Jupiter can
enter. When listening for Jupiter or the Sun, the radio will be tuned to find a clear channel.
Since frequencies more than a few kilohertz away from the center frequency may contain
interfering signals, these higher frequencies must be eliminated, which is the purpose of the low
pass filter (Flagg, 1999). The low pass filter passes low frequencies up to approximately 3.5
kHz and does not pass higher frequencies.
The audio amplifiers that follow the low-pass filter take the very weak audio signal from
the mixer and amplify it enough to drive either a set of headphones or some form of an external
amplified speaker system directly. The information that is sent to the headphones or speaker can
also be sent to a computer with the proper software and put in the form of a graph.
The key to successful fabrication of the JOVE receiver kit is the builder’s ability to
solder. The PC board should be populated according to Figure 2 in the appendix. The soldering
process was (and is) best accomplished by installing the larger parts first, leaving the small,
delicate devices until last. This particular assembly order gives the builder a chance to sharpen
his or her soldering skills before getting to the integrated circuits and transistors, which may be
damaged by excess heat. It was important to mount the components as close to the PC board as
possible without putting large amounts of strain on the leads. Some of the component leads
matched the PC-board hole spacing and the components went in flush with the board. In other
instances, the leads had to be formed to align with the holes.
Upon soldering all of the electric components and encasing the circuit board, it was
necessary to test and align the receiver. There are four ways to test and align the JOVE receiver,
some of which are more sophisticated than others. The first method is to simply listen to the
output of the receiver with headphones or an amplified speaker. The goal is to adjust some
variable capacitors, inductors, and resistors to obtain the loudest signal at a certain frequency.
The other methods are similar except rather than trusting human ears, a voltmeter, an
oscilloscope, or the JOVE strip-chart recorder software was used to measure the output. For the
receiver used in this project, an oscilloscope was used to test and align the receiver.
The Radio JOVE instruction manual suggests that eleven hours is sufficient time to
construct, test, and align the receiver (Flagg, 1999). However, it took roughly sixteen hours to
assemble the receiver for this research project and an additional hour to test and align the
receiver.
The Radio JOVE Antenna: The Radio JOVE antenna intercepts weak electromagnetic
waves that have traveled roughly 500 million miles from Jupiter to the Earth or 93 million miles
from the Sun. When this electromagnetic radiation strikes the wire antenna, a small RF voltage
is developed at the antenna terminals. Signals from each single dipole antenna are brought
together with a power combiner by means of two pieces of coaxial cable. The output of the
power combiner is delivered to the receiver by another section of coaxial transmission line
(Higgins et al., 1999).
The antenna consists of several types of components including wire, coaxial cable,
connectors, insulators, rope, supports, and hardware (See Figure 3). The antenna was
constructed from two identical half-wave dipole antennas and phasing them together with feed
line. The entire length of the dipole is therefore, equal to the length of 1/2 of the wavelength ()
of radiation to be detected. Thus each side of the dipole antenna is 1/4 wavelength long. Since
the Radio JOVE receiver is tuned to the frequency of 20.1 MHz, the wavelength is 14.925
meters (48.968 feet). A useful formula for calculating the half-wavelength for an ideal dipole in
free space for a specific frequency is:
/2 (in feet) = 492 / frequency (in MHz)
/2 (in meters) = 150 / frequency (in MHz).
For practical antennas, however, the measured values are smaller than the ideal values. This is a
result of resistance in the wire and end effects of the dipole. These two properties effectively
shorten the length at which the wire will most effectively receive radiation at a frequency of 20.1
MHz. To calculate the practical half-wavelength of antenna use the formula:
/2 (in feet) = 468 / frequency (in MHz)
/2 (in meters) = 142.5 / frequency (in MHz).
For the antenna to be an effective receptor of signals, the wire dipoles must be mounted
horizontally above the ground by about /4 feet (2.44 - 3.66 m is acceptable). This is
accomplished by attaching the wire to poles held up by support rope (Higgins et al., 1999).
The purpose of the coaxial transmission cable used in the antenna is to feed the
intercepted signal by the antenna to the receiver (Higgins et al., 1999). Therefore the coaxial
cable was attached to the antenna wire by solder joints. The coaxial cable has a center conductor
surrounded by a dielectric insulator and a copper braided shielding. These help conduct the
signal from the antenna to the receiver with a minimum loss of signal. Because the cable is not a
perfect conductor, the speed at which the signal propagates along the wire depends on the type
of dielectric insulation used in the cable. For the coax included in the JOVE kit, the velocity
factor is 66% (Higgins et al., 1999). Therefore, the proper lengths for cutting the coax must take
this factor into account.
The connectors used for the Radio JOVE are called F-type connectors and were manually
twisted onto the ends of the coax line. These connectors were used to connect the cables to the
power combiner and to the antenna input on the JOVE receiver (Higgins et al., 1999). Insulators
are needed to keep the antenna from shorting the received signals to ground. Six insulators were
needed for the antenna, one in the middle of each dipole, and one on each end. Insulators are
usually plastic or ceramic cylinders with holes cut in each end for the wire and rope supports.
The insulators included in the JOVE kit assembled for this project were plastic. PVC piping was
used for the antenna support poles. PVC is a cheap and lightweight support structure that is
portable and effective. Rope, toroids, and basic hardware such as nuts and bolts were also used
in the JOVE antenna. The magnetic toroids are needed for the antenna assembly to restrict
current flow along the outer surface of the coaxial cable shielding. This allows for optimal
reception by creating a better antenna pattern (Higgins et al., 1999).
It is important to find an acceptable area in which to setup the antenna after it has been
assembled: measure and cut the wire and rope, wrap the insulators, prepare and solder the
coaxial cable, install the connectors and toroids, and assemble the mounting structure. The
antenna system requires a relatively large area for proper setup. The minimum site requirements
are a 25 x 35 ft. flat area that has soil suitable for putting tent stakes into the ground. Because
the antenna system is sensitive to noise it is best not to set it up near any high-tension power
lines or close to buildings. Additionally, for safety reasons, it is best to keep the antenna away
from power lines during construction and operation (Higgins et al., 1999). A prime location is
in rural settings where the interference is minor. Due to the fact that many of the observations
occur at night, it is sensible to practice setting up the antenna during the day to make sure the
site is safe and easily accessible.
The Radio JOVE instruction manual suggests that construction time for the antenna and
to setup the antenna system the first time takes a little under five hours (Higgins et al., 1999).
However, for this project, the antenna construction alone took longer than the suggested time.
Results and Discussion
Due to the fact that this researcher did not begin the Radio JOVE project until recently,
no data have been collected with the newly constructed receiver and antenna. However, the
JOVE website has numerous examples of data that have been sent in from around the globe by
people who have all ready assembled their JOVE radio telescopes. A few of these examples will
be presented to illustrate what will, hopefully, result when data collection begins.
The first example of data is a comparison of a Solar burst that took place on June 20,
2001 (Figure 4 in the appendix). One of the graphs came from Maryland while the other came
from Hawaii. It is clear to see that the graphs compare rather well. While this is only one case,
the comparison is indicative that the JOVE radio telescope is a reliable astronomical tool. The
horizontal axis for both graphs in the figure represents time (UT = Universal time) and the
vertical axis can be thought of as a measure of the relative amount of intercepted radiation with a
frequency of 20.1 MHz. Another comparison of a different burst is shown in Figure 5.
The data shown in Figure 6 is a graph that was obtained at a community college in
Hawaii on February 3, 2001. The data displays radio emission activity of Jupiter and Io-B. The
final two figures in the appendix (Figures 7 and 8) illustrate Jupiter S-bursts on March 3, 2002.
Figure 8 is simply a continuation of figure 7.
Conclusion
Some of the most amazing scientific discoveries in the last 100 hundred years are the
direct result of radio astronomy. From phenomena as bizarre as black holes and quasars to the
development of low-noise radio receivers used by the satellite communications industry, radio
astronomers have contributed an immeasurable amount to the scientific community as well as
the human race as a whole. It would be absurd to assume that there is nothing more to gain from
radio astronomy, which is why it is important to continue studying the topic. The Radio JOVE
Project is an educational undertaking that provides students, teachers, amateurs, and others with
an excellent hands-on radio astronomy exercise while instilling some of the most basic skills
needed by professionals in the radio astronomy field. At a relatively low cost, anyone who has a
moderate background in electrical physics with some soldering experience can assemble the
Radio JOVE telescope to monitor 20.1 MHz radio emissions from Jupiter and the Sun.
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http://radiojove.gsfc.nasa.gov
APPENDIX OF FIGURES
Figure 1: Block Diagram of the Radio JOVE Receiver (from the Instructions Manual).
Figure 2: Electrical Component Population of the PC board
Figure 3: Radio JOVE Antenna (From the Instructions Manual).
Figure 4: JOVE Solar Burst Data (From the JOVE website).
Figure 5: Another Comparison of JOVE data (From the website).
Figure 6: Radio Emission data at 20.6 MHZ of Jupiter and Io-B (JOVE website).
Figure 7: S-Bursts from Jupiter on March 3, 2002 (JOVE website).
Figure 8: A continuation of Figure 7.