June 1964 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.
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One of the nice things
about these "What's Your EQ?" challenges that appeared in Radio-Electronics
magazine is that they tax your ability to recall basic electronics circuit
theory. The first one in the June 1964 issue requires you (spoiler here) to
apply Thévenin's theorem in order to arrive at the solution. You also need to
know about maximum power transfer which (another spoiler) requires the load
impedance to be the complex conjugate of the source impedance. "No Volts"
will make you very appreciative of today's high input impedance voltmeters; the
problem statement itself made my head hurt. Being aware of such issues often
meant the difference between success and failure when assessing television and
radio circuits. "Music-Intercom Trouble" almost certainly was inspired by a 1960
Electronics World
episode of "Mac's Radio Service Shop," entitled "Technician
or Consulting Engineer?." Have at it.
What's Your EQ?
Conducted by E. D. Clark
Three puzzlers for the student, theoretician and practical man. Simple? Double-check
your answers before you soy you've solved them. If you have an interesting or unusual
puzzle (with an answer) send it to us. We will pay $10 for each one accepted. We're
especially interested in service stinkers or engineering stumpers on actual electronic
equipment. We get so many letters we can't answer individual ones, but we'll print
the more interesting solutions - ones the original authors never thought of.
Write EQ Editor, Radio-Electronics, 154 West 14th Street, New York, N. Y. 10011
Maximum Power
Load RO is matched for maximum power output from the generator or
battery. However, it is desired to obtain maximum power in a new load to be connected
between A and B. What must be the value of the new load, and what is the power it
expends?
- H. D. Varadarajan
No Volts
A full-wave power supply has two silicon rectifiers in series on each side. Each
diode has a PIV rating of 400 volts. A 1,000-ohms-per-volt, rectifier type ac voltmeter
on its 300-volt range, with the hot test lead plugged into the OUTPUT jack to block
the dc component, is connected in turn across each diode to determine whether the
ac voltages across the two diodes are equal. They seem to be: the meter reads zero
across each diode. Why?
- Basil Barbee
Music-Intercom Trouble
In a combination background music and intercom system, the speaker is connected
so that when switch S1 is depressed it will stop the music and connect the speaker
to the input of the intercom amplifier to initiate a call. However, the circuit
as shown here is not usable in the CALL position. What is the trouble symptom and
why does it happen? What can be done to correct it?
Capacitance effects of wiring and switches are unobjectionable. For simplicity,
switching for talkback from the intercom is not shown.
- Wayne Lemons
Quizzes from vintage electronics magazines such as Popular
Electronics, Electronics-World, QST,
Radio-Electronics, and Radio News
were published over the years - some really simple and others not so simple. Robert P. Balin
created most of the quizzes for Popular Electronics. This is a listing
of all I have posted thus far.
- RF Cafe Quiz #71:
Tech Headlines for Week of 3/13/2023
- RF Cafe Quiz #70:
Analog &
RF Filter Basics
- RF Cafe Quiz #69:
RF
Electronics Basics
- RF Cafe Quiz #68:
RF & Analog Company Mergers & Acquisitions in 2017
- RF Cafe Quiz #67:
RF & Microwave Company Name Change History
- RF Cafe Quiz #66:
Spectrum and Network Measurements
- RF Cafe Quiz #65:
Troubleshooting & Repairing Commercial Electrical Equipment
- RF Cafe Quiz #64:
Space-Time Adaptive Processing for Radar
- RF Cafe Quiz #63:
Envelope Tracking Power Amplifiers
- RF Cafe Quiz #62:
Stimson's Introduction to Airborne Radar
- RF Cafe Quiz #61:
Practical Microwave Circuits
- RF Cafe Quiz #60:
Ten Essential Skills for Electrical Engineers
- RF Cafe Quiz #59:
Microwave Circulator Design
- RF Cafe Quiz #58:
Microwave and Millimeter-Wave Electronic Packaging
- RF Cafe Quiz #57:
Frequency-Agile Antennas for Wireless Communications
- RF Cafe Quiz #56:
Tube Testers
and Electron Tube Equipment
- RF Cafe Quiz #55:
Conquer
Radio Frequency
- RF Cafe Quiz #54:
Microwave Mixer Technology and Applications
- RF Cafe Quiz #53:
Chipless RFID Reader Architecture
- RF Cafe Quiz #52:
RF and Microwave Power Amplifiers
- RF Cafe Quiz #51:
Antennas and Site Engineering for Mobile Radio Networks
- RF Cafe Quiz #50:
Microstrip Lines and Slotlines
- RF Cafe Quiz #49:
High-Frequency Integrated Circuits
- RF Cafe Quiz #48:
Introduction to Infrared and Electro-Optical Systems
- RF Cafe Quiz #47:
LCP for Microwave Packages and Modules
- RF Cafe Quiz #46:
RF, Microwave, and Millimeter-Wave Components
- RF Cafe Quiz #45:
Dielectric and Thermal Properties of Materials at Microwave Frequencies
- RF Cafe Quiz #44:
Monopulse Principles and Techniques
- RF Cafe Quiz #43:
Plasma Antennas
- RF Cafe Quiz #42: The Micro-Doppler
Effect in Radar
- RF Cafe Quiz #41: Introduction
to RF Design Using EM Simulators
- RF Cafe Quiz #40: Introduction
to Antenna Analysis Using EM Simulation
- RF Cafe Quiz #39: Emerging
Wireless Technologies and the Future Mobile Internet
- RF Cafe Quiz #38: Klystrons,
Traveling Wave Tubes, Magnetrons, Crossed-Field Amplifiers, and Gyrotrons
- RF Cafe Quiz #37: Component
Reliability for Electronic Systems
- RF Cafe Quiz #36: Advanced
RF MEMS
- RF Cafe Quiz #35: Frequency
Synthesizers: Concept to Product
- RF Cafe Quiz #34: Multi-Gigabit
Microwave and Millimeter-Wave Wireless Communications
- RF Cafe Quiz #33: Battlespace
Technologies: Network-Enabled Information Dominance
- RF Cafe Quiz #32: Modern Communications
Receiver Design and Technology
- RF Cafe Quiz #31: Quantum
Mechanics of Nanostructures
- RF Cafe Quiz #30: OFDMA System
Analysis and Design
- RF Cafe Quiz #29: Cognitive
Radar
- RF Cafe Quiz #28: Human-Centered
Information Fusion
- RF Cafe Quiz #27: Remarkable
Engineers
- RF Cafe Quiz #26: Substrate
Noise Coupling in Analog/RF Circuits
- RF Cafe Quiz #25: Component
Reliability for Electronic Systems
- RF Cafe Quiz #24: Ultra Low
Power Bioelectronics
- RF Cafe Quiz #23: Digital
Communications Basics
- RF Cafe Quiz #22: Remember
the Basics?
- RF Cafe Quiz #21: Wireless
Standards Knowledge
- RF Cafe Quiz #20: Famous First
Names
- RF Cafe Quiz #19: Basic Circuit
Theory
- RF Cafe Quiz #18: Archaic
Scientific Words & Definitions
- RF Cafe Quiz #17: Inventors &
Their Inventions
- RF Cafe Quiz #16: Antennas
- RF Cafe Quiz #15: Numerical
Constants
- RF Cafe Quiz #14: Oscillators
- RF Cafe Quiz #13: General
Knowledge
- RF Cafe Quiz #12: Electronics
Corporations Headquarters
- RF Cafe Quiz #11: Famous Inventors &
Scientists
- RF Cafe Quiz #10: A Sampling
of RF & Wireless Topics
- RF Cafe Quiz #9: A Smorgasbord
of RF Topics
- RF Cafe Quiz #8: Hallmark Decades
in Electronics
- RF Cafe Quiz #7: Radar Fundamentals
- RF Cafe Quiz #6: Wireless Communications
Fundamentals
- RF Cafe Quiz #5: Company Logo
Recognition
- RF Cafe Quiz #4: General RF
Topics
- RF Cafe Quiz #3: General RF/Microwave
Topics
- RF Cafe Quiz #2: General RF
Topics
- RF Cafe Quiz #1: General RF
Knowledge
- Vacuum Tube Quiz,
February 1961 Popular Electronics
- Kool-Keeping Kwiz, June
1970 Popular Electronics
- Find the Brightest
Bulb Quiz, April 1960 Popular Electronics
-
Where Do the Scientists Belong? - Feb 19, 1949 Saturday Evening Post
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-
What's
Your EQ? - February 1962 Radio-Electronics
-
What's
Your EQ? - March 1962 Radio-Electronics
-
What's
Your EQ? - July 1961 Radio-Electronics
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What's
Your EQ? - August 1961 Radio-Electronics
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Can You
Name These Strange Electronic Effects? - August 1962 Radio-Electronics
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What's
Your EQ? - September 1961 Radio-Electronics
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What's
Your EQ? - September 1962 Radio-Electronics
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What's Your EQ? - October 1961 Radio-Electronics
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What's Your EQ? - November 1961 Radio-Electronics
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What's Your EQ? - March 1964 Radio-Electronics
-
What's Your EQ? - April 1962 Radio-Electronics
-
What's Your EQ? - May 1962 Radio-Electronics
-
What's Your EQ? - June 1962 Radio-Electronics
-
What's Your EQ? - April 1967 Radio-Electronics
-
What's Your EQ? - March 1967 Radio-Electronics
-
What's Your EQ? - December 1964 Radio-Electronics
-
What's Your EQ? - January 1967 Radio-Electronics
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Wanted: 50,000 Engineers - January 1953 Popular Mechanics
-
What's Your EQ? - August 1964 Radio-Electronics
- Voltage Quiz
- December 1961 Popular Electronics
-
What is It? - June 1941 Popular Science
- What Do You Know
About Resistors? - April 1974 Popular Electronics
-
What's Your EQ? - September 1963 Radio-Electronics
- Potentiometer Quiz - September
1962 Popular Electronics
-
Mathematical Bafflers - March 1965 Mechanix Illustrated
- Op Amp Quiz -
October 1968 Popular Electronics
- Electronic "A"
Quiz - April 1968 Popular Electronics
-
What's Your EQ? - May 1961 Radio-Electronics
-
Popular Science Question Bee - February 1939 Popular Science
-
What is It? - A Question Bee in Photographs - June 1941 Popular Science
-
What's Your EQ? - June 1961 Radio-Electronics
-
What's Your EQ? - June 1964 Radio-Electronics
-
What's Your EQ? - May 1964 Radio-Electronics
-
What's Your EQ? - August 1963 Radio-Electronics
-
What's Your EQ? - May 1963 Radio-Electronics
- Bridge
Function Quiz - September 1969 Radio-Electronics
-
What's Your EQ? - March 1963 Radio-Electronics
-
What's Your EQ? - February 1967 Radio-Electronics
-
Circuit Quiz - June 1966 Radio-Electronics
-
What's Your EQ? - June 1966 Radio-Electronics
- Electronics
Mathematics Quiz - June 1969 Popular Electronics
- Brightest
Light Quiz - April 1964 Popular Electronics
-
What's Your EQ? - April 1963 Radio-Electronics
- Electronics "B" Quiz
- July 1969 Popular Electronics
- Ohm's Law Quiz
- March 1969 Popular Electronics
-
Antenna Quiz - November 1962 Electronics World
- Color Code Quiz
- November 1967 Popular Electronics
- CapaciQuiz
- August 1961 Popular Electronics
- Transformer
Winding Quiz - December 1964 Popular Electronics
-
Audiophile Quiz - November 1957 Radio-electronics
- Capacitor
Function Quiz - March 1962 Popular Electronics
- Greek Alphabet
Quiz - December 1963 Popular Electronics
- Circuit
Designer's Name Quiz - July 1968 Popular Electronics
-
Sawtooth Sticklers Quiz - November 1960 Radio-Electronics
-
Elementary
Radio Quiz - December 1947 Radio-Craft
- Hi-Fi
Quiz - October 1955 Radio & Television News
- Electronics Physics
Quiz - March 1974 Popular Electronics
- A Baffling Quiz
- January 1968 Popular Electronics
- Electronics IQ
Quiz - May 1967 Popular Electronics
- Plug and Jack
Quiz - December 1967 Popular Electronics
- Electronic
Switching Quiz - October 1967 Popular Electronics
- Electronic
Angle Quiz - September 1967 Popular Electronics
- International
Electronics Quiz - July 1967 Popular Electronics
- FM Radio
Quiz - April 1950 Radio & Television News
- Bridge Circuit
Quiz -December 1966 Popular Electronics
- Diode Function
Quiz - August 1965 Popular Electronics
- Diagram Quiz,
August 1966 Popular Electronics
- Quist Quiz - November
1953 QST
- TV Trouble Quiz,
July 1966 Popular Electronics
- Electronics History Quiz,
December 1965 Popular Electronics
- Scope-Trace Quiz,
March 1965 Popular Electronics
-
Electronic
Circuit Analogy Quiz, April 1973
-
Test Your Knowledge of Semiconductors, August 1972 Popular Electronics
- Ganged Switching
Quiz, April 1972 Popular Electronics
- Lamp Brightness
Quiz, January 1969 Popular Electronics
- Lissajous
Pattern Quiz, September 1963 Popular Electronics
- Electronic
Quizoo, October 1962 Popular Electronics
- Electronic
Photo Album Quiz, March 1963 Popular Electronics
- Electronic
Alphabet Quiz, May 1963 Popular Electronics
- Quiz: Resistive?
Inductive? or Capacitive?, October 1960 Popular Electronics
- Vector-Circuit
Matching Quiz, June 1970 Popular Electronics
- Inductance
Quiz, September 1961 Popular Electronics
- RC Circuit Quiz,
June 1963 Popular Electronics
- Diode Quiz, July
1961 Popular Electronics
- Electronic
Curves Quiz, February 1963 Popular Electronics
- Electronic
Numbers Quiz, December 1962 Popular Electronics
- Energy Conversion
Quiz, April 1963 Popular Electronics
- Coil Function
Quiz, June 1962 Popular Electronics
-
Co-Inventors Quiz - January 1965 Electronics World
-
"-Tron" Teasers Quiz - October 1963 Electronics World
- Polarity Quiz
- March 1968 Popular Electronics
-
Television
I.Q. Quiz - October 1948 Radio & Television News
- Amplifier Quiz
Part I - February 1964 Popular Electronics
- Semiconductor
Quiz - February 1967 Popular Electronics
- Unknown
Frequency Quiz - September 1965 Popular Electronics
- Electronics
Metals Quiz - October 1964 Popular Electronics
- Electronics
Measurement Quiz - August 1967 Popular Electronics
- Meter-Reading
Quiz, June 1966 Popular Electronics
- Electronic
Geometry Quiz, January 1965 Popular Electronics
- Electronic
Factor Quiz, November 1966 Popular Electronics
- Electronics
Math Quiz, November 1965 Popular Electronics
- Series Circuit
Quiz, May 1966 Popular Electronics
- Electrochemistry
Quiz, March 1966 Popular Electronics
- Biz
Quiz: Test Your Sales Ability - April 1947 Radio News
- Electronic
Analogy Quiz, November 1961 Popular Electronics
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Answers to What's Your EQ?
Maximum Power
The first operation is to reduce the circuit to its equivalent Thévenin generator.
To do this, we first find the Thévenin voltage at point A.
EA = E x 10/(10 + 10) = 50 volts = ETH
Next, looking back into the circuit from points A and B, with E reduced to zero,
we see RO and RInt in parallel.
(10 x 10)/(10 + 10) = 5 ohms = RTH
Since the "internal resistance" is now 5 ohms, the new load must be 5 ohms for
maximum power transfer. Using any of the power formulas, (I2R, for instance)
the power in the new load is now found to be:
P = (50/10)2 x 5 = 125 watts
No Volts
Silicon diodes have a very high back resistance, much higher than the 300,000-ohm
resistance of the meter. The diode of a series pair that is not shunted by the meter
has to withstand virtually all of the drop, since its back resistance is so much
higher than that of the meter. The shunted diode then has a negligible drop across
it. While the PIV rating of the unshunted diode is temporarily exceeded during the
test, it is undamaged due to its conservative rating.
Music-Intercom Trouble
Background music will overload the intercom amplifier when S is in CALL position.
This occurs because of a built-in ground loop and the all-too-prevalent idea that
a common or ground lead is "cold" just because it happens to be in the return circuit.
To make it easier to see how this ground loop occurs, we have taken the circuit
and substituted a battery for the background music amplifier and a voltmeter for
the intercom amplifier. Resistors are substituted for the speaker loads. With the
arbitrary values shown, we can see that at point A there is a 1-volt drop across
the parallel resistances of the ground wires. With the switch in the CALL position,
this voltage drop will be indicated on the meter.
In the music-intercom system this voltage is fed directly into the intercom amplifier
and amplified several hundred times.
The obvious and simple solution is to use a DPDT switch for S so that both sides
of the speaker will be disconnected when a call is made.
Posted July 24, 2023
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