# Unknown Frequency QuizSeptember 1965 Popular Electronics

 September 1965 Popular Electronics Table of Contents Wax nostalgic about and learn from the history of early electronics. See articles from Popular Electronics, published October 1954 - April 1985. All copyrights are hereby acknowledged.

Lots of old-time sci-fi movies and TV shows liked to display Lissajous patterns on oscilloscopes when an authentic high tech look was needed in a scene. Every engineer, technician, and physicist in the world - me included - roll his or her eyes at the sight of such a lame attempt to impress the public. Of course the truth is the first time I saw a Lissajous pattern gyrating on an o-scope screen, I was mesmerized. The need to crank on the signal generator knobs and take control of the electroluminescent object d'art was overwhelming. Now, in the same manner that watching the first couple Space Shuttle launches was a thrill not to be missed and then became just another launch, so, too, is watching a live Lissajous pattern on a scope - it's just another Lissajous. Except, well, that's not quite so - at least for me. I always eagerly viewed Shuttle launches and landings (in the good old days when the U.S. had a manned space program), and I still can't pass up the opportunity to play with Lissajous patterns on an oscilloscope.

Unknown Frequency Quiz

By Robert P. Balin

An unknown frequency can be accurately determined by analyzing the Lissajous pattern it forms when combined with a known frequency. Lissajous patterns can quickly tell you the ratio of the frequencies applied to the vertical and horizontal inputs of an oscilloscope. See if you can do problems 1-10. Ratios and unknown frequencies are given on page 95.

(Hint) : In problem 1, for example, there are three-and-one-half vertical cycles as indicated by the peaks at the top and bottom of the pattern, and two horizontal cycles as indicated by the peaks on either side. This combination or vertical-to-horizontal frequency ratio is 3.5 to 2, or 7 to 4. Therefore, if the vertical frequency is 2800 cycles, the unknown horizontal frequency must be 1600 cycles to produce the pattern shown.

Popular Electronics published many quizzes over the years - some really simple and others not so simple. Robert Balin created many of the quizzes. This is a listing of all I have posted thus far.

 Electronics IQ Quiz - May 1967 Plug and Jack Quiz - December 1967 Electronic Switching Quiz - October 1967 Electronic Angle Quiz - September 1967 International Electronics Quiz - July 1967 Bridge Circuit Quiz -December 1966 Diode Function Quiz - August 1965 Diagram Quiz, August 1966 TV Trouble Quiz, July 1966 Electronics History Quiz, December 1965 Scope-Trace Quiz, March 1965 Electronic Circuit Analogy Quiz, April 1973 Test Your Knowledge of Semiconductors, August 1972 Ganged Switching Quiz, April 1972 Lamp Brightness Quiz, January 1969 Lissajous Pattern Quiz, September 1963 Electronic Quizoo, October 1962 Electronic Photo Album Quiz, March 1963 Electronic Alphabet Quiz, May 1963 Quiz: Resistive? Inductive? or Capacitive?, October 1960 Vector-Circuit Matching Quiz, June 1970 Inductance Quiz, September 1961 RC Circuit Quiz, June 1963 Diode Quiz, July 1961 Electronic Curves Quiz, February 1963 Electronic Numbers Quiz, December 1962 Energy Conversion Quiz, April 1963 Coil Function Quiz, June 1962 Semiconductor Quiz - February 1967 Unknown Frequency Quiz - September 1965 Electronics Metals Quiz - October 1964 Electronics Measurement Quiz - August 1967 Meter-Reading Quiz, June 1966 Electronic Geometry Quiz, January 1965 Electronic Factor Quiz, November 1966 Electronics Math Quiz, November 1965 Series Circuit Quiz, May 1966 Electrochemistry Quiz, March 1966 Electronic Analogy Quiz, November 1961 Electronic Coupling Quiz, August 1973 Electronics Analogy Quiz, August 1960 Audio Quiz, April 1955 Electronic Unit Quiz, May 1962 Capacitor Circuit Quiz, June 1968 Quiz on AC Circuit Theory, December 1970 Magnetic Phenomena Quiz, February 1962 Electronics Geography Quiz, April 1970 Electronic Menu Quiz, August 1963 Electronic Noise Quiz, August 1962 Electronic Current Quiz, October 1963 Electronic Inventors Quiz, November 1963 Resistor Function Quiz, January 1962 Electronic Measurement Quiz, January 1963 Vacuum Tube Quiz, February 1961 Kool-Keeping Kwiz, June 1970

1)  7:4, 1600 cycles

2)  3:2, 750 cycles

3)  7:3, 600 cycles

4)  9:4, 540 cycles

5)  5:6, 1200 cycles

6)  4:5, 48 cycles

7)  7:6, 3600 cycles

8)  4:3, 160 cycles

9)  5:7, 4900 cycles

10)  8:3, 2400 cycles

Posted September 21, 2018

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