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What's Your EQ?May 1964 Radio-Electronics

 May 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.

All three questions in the May 1964 Radio-Electronics magazine "What's Your EQ?" challenge should not be too difficult for most RF Cafe visitors. EQ, by the way, stands for "Electronics Quotient." For the first one, you might want to make use of the Delta-Wye converter in the newly released (and free) Espresso Engineering Workbook™. With the Voltage Divider, don't bother trying to write multiple equations in multiple unknowns. By inspection you can deduce what the voltage drop across the 2.5 kΩ resistor are, then knowing that the current through all resistors is the same, figure out the required values of R1 and R3. Finally, sum all the resistances and multiply by the current. Done. I have to admit to not getting the Doodle answer. If I had time, I'd do the oscilloscope thing to verify the author's solution.

What's Your EQ?

Three puzzlers for the student, theoretician and practical mono Simple? Double-check your answers before you say 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

Untermination

Fig. 1 shows an unterminated tee network and Fig. 2 shows an unterminated pi network. Can you determine the electrical characteristic that the two networks have in common? - K. Collins

Voltage Divider

In the diagram (to the left), R2 and R4 are each 2,500 ohms. Readings taken with voltmeters (V) assumed to have infinite impedance show 70 volts across R1 plus R2, and 30 volts across R2 plus R3. What is the input voltage (EIN)? - Harold J. Turner, Jr.

Doodles

How do you produce this waveform on an oscilloscope? - Lee H. Stanton

Answers shown below

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 Quizzes 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 Vintage Electronics Magazine Quizzes Quiz on AC Circuit Theory, December 1970 Popular Electronics Magnetic Phenomena Quiz, February 1962 Popular Electronics Electronics Geography Quiz, April 1970 Popular Electronics Electronic Menu Quiz, August 1963 Popular Electronics Electronic Noise Quiz, August 1962 Popular Electronics Electronic Current Quiz, October 1963 Popular Electronics Electronic Inventors Quiz, November 1963 Popular Electronics Resistor Function Quiz, January 1962 Popular Electronics Electronic Measurement Quiz, January 1963 Popular Electronics Vintage Electronics Magazine Quizzes Electronic Coupling Quiz, August 1973 Popular Electronics Electronics Analogy Quiz, August 1960 Popular Electronics Audio Quiz, April 1955 Popular Electronics Electronic Unit Quiz, May 1962 Popular Electronics Capacitor Circuit Quiz, June 1968 Popular Electronics Vintage Electronics Magazine Quizzes What's Your EQ? - September 1961 Radio-Electronics What's Your EQ? - September 1962 Radio-Electronics What's Your EQ? - October 1961 Radio-Electronics What's Your EQ? - November 1961 Radio-Electronics 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 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 19680 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

Untermination

Each network has a characteristic impedance of 600 ohms. This can be determined by connecting a 600-ohm load resistor across the output terminals of each and measuring the effective resistance between the input terminals of each network. Both networks will have an input resistance of 600 ohms. Since this is the same value as the load resistance, the characteristic impedance of each network is said to be 600 ohms.

In the tee network, the 600-ohm load resistor is in series with the 200 ohm resistor on the right-hand side of the network, making the equivalent of 800 ohms. This resistance is in combination with the 800-ohm shunt resistor, making a series-shunt combination that equals 400 ohms. By adding the left-hand resistance of 200 ohms to 400 ohms, the resistance between the input terminals is found to be 600 ohms. Since this is the same value as the load resistor, the characteristic impedance of the tee network is 600 ohms.

In the pi network, a 600-ohm load resistor is in parallel with the right-hand 1,800-ohm shunt resistor. This combination equals 450 ohms and is in series with the 450-ohm network resistor, making a total of 900 ohms. The left-hand shunt resistance of 1,800 ohms is now in parallel with 900 ohms, which makes the input resistance across the input terminals 600 ohms. Since the load resistance of 600 ohms equals the input resistance, the characteristic impedance of the pi network is 600 ohms.

Note:

By using the Wye-Delta or Delta-Wye transformation, it can also be shown that the two networks are equivalent. The tee and pi networks are examples of Wye and Delta networks respectively. - Editor

Download the Espresso Engineering Workbook™ for a Delta-Wye converter.

Voltage Divider

This puzzle is not as hard as it seems at first glance. Since the four resistors are connected in series, the same current must flow through each. We see that R4 has the same resistance as R2. Therefore the drop across R3 plus R4 is the same as the drop across R2 plus R3 - 30 volts. The total input voltage is 100.

Doodles

If the horizontal input of your scope is not disconnected from the horizontal amplifier when using internal sweep (about 10 or 12 cycles), simply connect the 60-cycle test signal to the vertical input, and also to the horizontal input through a small capacitor for a 90° phase shift.

If the horizontal input is disconnected when using internal sweep, connect the capacitor from the 60-cycle test to the horizontal amplifier internally with a clip lead.

An additional solution for "Doodles" was included in the August 1964 issue:

Doodles in May

The scope trace in the May 1964 issue can also be produced by quickly moving the HORIZONTAL POSITION knob when the same frequency is put into both horizontal and vertical inputs, out of phase so as to produce a circular Lissajous figure. By noting whether the cusps are up or down, you can figure out whether the spot is moving clock-wise or counterclockwise. Thus you can tell which input, horizontal or vertical, is leading and which is lagging. I have generated this pattern for the purpose many times.

- Paul Penfield, Jr.

Posted July 7, 2023