JOVE RJ1.1 User manual
Assembly Manual
JOVE
RJ1.1 Receiver Kit
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JOVE
RJ1.1 Receiver Kit
Assembly Manual
March 1999
Receiver Kit and Manual
developed for NASA JOVE Project
by
Richard S. Flagg, RF Associates
1721-I Young Street
Honolulu, Hawaii 96826
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Contents
Theory of Operation .......................................................................................1
Components ....................................................................................................2
Circuit Diagrams.............................................................................................7
Tools .............................................................................................................12
Soldering.......................................................................................................13
The Work Area..............................................................................................13
Identifying Parts ...........................................................................................13
Assembling the Enclosure ............................................................................18
Wiring the PC Board ....................................................................................21
Assembly of the PC Board and Enclosure....................................................24
Testing and Alignment..................................................................................28
Troubleshooting ............................................................................................34
Appendix A: Soldering Techniques ..............................................................39
Appendix B: Resistor Color Code ................................................................41
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1
Radio JOVE
You are about to embark on building a short-wave receiver which will pick
up radio signals from the planet Jupiter and also from the Sun. This receiver
contains over 100 electronic components and pieces of hardware. Fabrica-
tion will include the handling of small, delicate, electronic parts, most of
which will be mounted and soldered on a printed circuit (PC) board.
The radio uses many different types of electronic components, with each
part performing a different job. However, before discussing these compo-
nents and what they do, we will look at the overall receiver (depicted in the
block diagram in Figure 1).
CONSTRUCTION TIME ESTIMATES
Part Identification approx. 1 hr.
Receiver Construction approx. 9 hrs.
Testing and Alignment approx. 1 hr.
Total Time approx. 11 hrs.
THEORY OF OPERATION
Radio signals from Jupiter are very weak—they produce less than a mil-
lionth of a volt (1 microvolt, 1µV) at the antenna terminals of the receiver.
These weak radio frequency (RF) signals must be amplified by the receiver
and converted to audio signals of sufficient strength to drive headphones or a
loudspeaker. The receiver also serves as a narrow filter, tuned to a specific
frequency to hear Jupiter while at the same time blocking out strong earth
based radio stations on other frequencies. The receiver and its accompany-
ing antenna are designed to operate over a narrow range of short-wave fre-
quencies centered on 20.1 MHz (megahertz). This frequency range is opti-
mum for hearing Jupiter signals.
Antenna
The antenna intercepts weak electromagnetic waves which have traveled
some 500 million miles from Jupiter to the Earth. When these electromag-
netic waves strike the wire antenna, a tiny RF voltage is developed at the
2
antenna terminals. Signals from the antenna are delivered to the antenna
terminals of the receiver by a coaxial transmission line.
RF Bandpass Filter and Preamplifier
Signals from the antenna are filtered to reject strong out-of-band interference
and are then amplified using a junction field effect transistor (JFET). This
transistor and its associated circuitry provide additional filtering and amplify
incoming signals by a factor of 10. The receiver input circuit is designed to
efficiently transfer power from the antenna to the receiver while developing
a minimum of noise within the receiver itself.
Local Oscillator and Mixer
The local oscillator (LO) and mixer perform the important task of converting
the desired radio frequency signals down to the range of audio frequencies.
The local oscillator generates a sinusoidal voltage wave form at a frequency
in the vicinity of 20.1 MHz. The exact frequency is set by the front panel
tuning control. Both the amplified RF signal from the antenna and the LO
frequency are fed into the mixer. The mixer develops a new signal which is
the arithmetic difference between the LO and the incoming signal frequency.
Suppose the desired signal is at 20.101 MHz and the LO is tuned to 20.100
MHz. The difference 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.
Low Pass Filter
To eliminate interfering stations at nearby frequencies, we use a filter which
is like a window a few kilohertz wide through which Jupiter signals 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. This is the purpose of the low pass filter following the
mixer. It passes low (audio) frequencies up to about 3.5 kHz and attenuates
higher frequencies.
Audio Amplifiers
The purpose of the audio amplifiers following the low-pass filter is to take
3
RF
Preamp
J310
LO / Mixer
NE602
Audio
Preamp
LM387
5 Pole
Low Pass
Filter
RF
Bandpass
Filter
Antenna
Volume
Tuning
(20.1 MHz +/- 150 kHz)
JOVE RJ1.1
Jupiter Receiver
Block Diagram
Audio
Amp
Audio
Out 1
External
Amplified
Speaker
20.000 MHz
Test
Oscillator
Audio
Out 2
Figure 1. JOVE receiver block diagram
4
the very weak audio signal from the mixer and amplify it enough to drive
headphones directly, or to drive an external amplified speaker assembly.
COMPONENTS
The JOVE receiver uses many different electronic components (Figure 2)
including wires, resistors, capacitors, inductors, diodes, transistors and inte-
grated circuits. Each performs different functions.
Wires are made of conducting metal—they direct the flow of electrical
current from one place to another. Since wire is a good conductor, it has a
low resistance to the flow of electricity. The printed circuit (PC) board used
in this kit uses traces of copper etched on an insulating fiberglass back plane
in place of individual wires.
Resistors conduct electrical current, but they are designed to impede the
flow of electrons. This characteristic of resistance limits the amount of
current flow according to Ohm’s law. Resistors dissipate electrical power by
generating heat. The value of a resistor is given in Ohms (Ω), while its
maximum power dissipation is given in watts. There are fixed resistors and
variable resistors. Two variable resistors are used in this kit—one as the
volume control and the other as the tuning control. The fixed resistors in this
kit have several different values of resistance, but they are all 1/4 watt size.
See Appendix B for reading resistor value color codes.
Capacitors appear as an open circuit to direct current (DC) but pass audio
and radio frequency signals. The value of a capacitor is given in Farads (F),
although it is most common to use capacitors with values in the range of
microFarads (µF) or picoFarads (pF). Since the capacitor is physically made
of two conducting plates separated by a very thin layer of insulation, it is
possible for an electrical voltage to arc between the plates and destroy the
capacitor. For this reason capacitors have a maximum voltage rating. Ca-
pacitors store energy in the electrical field between the plates but do not
dissipate power like resistors.
Inductors are simply coils of wire which pass direct current and have the
property of resisting changes in current flow. The value of inductance is the
Henry (H), although it is most common to use coils whose inductance is
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