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Electronic Puzzle Square
January 1945 Radio-Craft

January 1945 Radio-Craft

Janaury 1945 Radio Craft Cover - RF Cafe[Table of Contents]

Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Craft, published 1929 - 1953. All copyrights are hereby acknowledged.

This Electronic Puzzle Square, compliments of Lt. C.K. Johnson, appeared in the January 1945 issue of Radio-Craft magazine. It consists of electronics-related numerical questions whose answers, if correct, create a 4x4 matrix whose columns, rows, and long diagonals all add up to 45. Non-integer answers need to be rounded according to standard rules (do not just truncate). In case you left your slide rule at the office, a link is provided to assist with Q2. The biggest head scratcher question is Q4, since it requires the conversion from polar to rectangular coordinates, but hey, you're an engineer (or a crack technician). Having Euclid on-hand for Q5 might be helpful. A link is provided to a copper wire parameter table for Q9. Have fun.

Here is another Electronic Puzzle Square from the July 1945 issue.

Electronic Puzzle Square

Electronic Puzzle Square, January 1945, Radio-Craft - RF CafeBy Lt. C. K. Johnson

Here is a new idea in a Magic Square. Work problem No. 1 and put the answer in square No. 1. The answer to problem 2 goes in square 2, etc. When all 16 problems are completed, the rows, columns diagonals and various other combinations will total a number which is the type number of a popular power amplifier triode frequently used push-pull to give a power output of about 18 watts with 275 volts on the plate.

The numbers add up to 45 in every direction, if answers are correct.


1. The total resistance between A and B is ____ ohms.

Electronic Puzzle Square Q1 - RF Cafe

2. On a slide rule, 64 on the right hand side of the A scale is directly over ____ on the D scale.

3. The pentode is a ____ element tube.

4. 21.18/8.1° would equal ____ +3j in rectangular coordinates.

5. If a regular hexagon is inscribed in a circle whose radius is one inch, the perimeter of the hexagon is ____ inches.

6. What is the voltage between A and B?

Electronic Puzzle Square Q6 - RF Cafe

7. Two 12 volt batteries hooked in parallel will give ____ volts.

8. 0.142857 is the reciprocal of _____.

9. B&S gage bare copper wire No. ____ has a circular mil area of 1,288 and at 25 °C. has a resistance of 8.1 ohms per 1,000 feet. (see table here)

10. To find wavelength in meters when frequency in kilocycles is known, we have a formula λ = (c x 105)/f . What digit does "c" replace?

11. In the R.M.A. color code, silver represents a tolerance of what percent?

12. What is the total capacitance in mfd. between A and B?

Electronic Puzzle Square Q12 - RF Cafe

13. Effective voltage (in alternating current of sine-wave form) is to average voltage as 10 is to ____ .

14. What will be the voltage across the 1-megohm resistor exactly 1.967 seconds after the switch (S1) is closed, allowing current to enter the resistor-condenser combination?

Electronic Puzzle Square Q14 - RF Cafe

15. In this circuit the problem is to find the current in milliamperes if 1.62 watts is dissipated in the 500-ohm resistor.

16. Yellow is ____ in the color code.





















Posted  February 25, 2021

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Copyright: 1996 - 2024


    Kirt Blattenberger,


RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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