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What's Your EQ?
November 1964 Radio-Electronics

November 1964 Radio-Electronics

November 1964 Radio-Electronics Cover - RF Cafe[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.

I have to admit to not feeling up to taking the challenge on all of these "What's Your EQ?" circuits appearing in Radio-Electronics magazine. Usually, I dive right in and give them a shot. The first is just an explanation for a problem which appeared in an article the June 1964 issue entitled "Double Bridge Sensitivity." You can read it at the link provided. Ferris Wheel is simple enough if you carefully note the connections. Don't make it more difficult than it really is (hint: add voltages). "Two Meters" is worded a bit deceivingly by stating "two pulsating contacts," when it would be more helpful to call it a single set of pulsating contacts. That's it. Good luck to you.

What's Your EQ?

What's Your EQ (Electronics Quotient)?, November 1964 Radio-Electronics - RF CafeConducted by E. D. Clark

Three puzzlers for the student, theoretician and practical man. 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.

Answers to this month's puzzle are on page 95.

Double Bridge Sensitivity - RF Cafe

Double Bridge Sensitivity

Mr. E. D. Clark, our EQ editor, comments on the item of the above article title which was on page 36 of the June issue (I do not have it posted): A bridge with two variable arms will yield double the output of a bridge with a single variable arm, if the detector has infinite resistance. If the detector is a current-operated device such as a d'Arsonval voltmeter or ammeter (that is, doesn't have infinite resistance), the output ratio is greater than 2:1! Using the same values as in the original EQ and reducing each circuit to its Thévénin equivalent, we get simplified schematics like the ones in the diagram. For instance, a 1-volt, 100-ohm-per-volt voltmeter or 10-ma (100-ohm) milliammeter would yield the following readings: 

The ratio is slightly greater than 2:1. Now, going to the extreme, using a "perfect" (zero-resistance) ammeter:

The output ratio is now 2.5: 1.

- E. D. Clark

 

Ferris Wheel - RF CafeFerris Wheel

This network has six resistors connected as shown to six independent 2-volt sources (considered ideal). What is the voltage at the junction V1?

- E. D. Clark

 

Two Meters - RF CafeTwo Meters

The diagram shows a series circuit which includes two pulsing contacts, a dc ammeter (d'Arsonval type), an ac ammeter (rf type), and a 12-ohm resistor. The circuit has a total dc resistance of 12 ohms and no residual reactance. If the contacts are adjusted to open and close at the rate of 60 pulses per second, and pulse width is 2/300 second, what reading will be shown on each ammeter?

- Kendall Collins

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

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Vintage Electronics Magazine Quizzes

Answers to What's Your q?

This month's puzzles are on page 57

Ferris Wheel

From Kirchhoff's current law, we see that the algebraic sum of the currents into any junction is equal to zero. As the outer end of all resistors is at a fixed voltage, V1 is the only unknown. Assuming V1 to be 1 volt (any value would do), the current directions are assigned as shown. The equation for the junction currents is now written:

Using LCD of 12, then eliminating denominators:

Collecting terms:    66 - 22V1 = 0    V1 = 3

All branch currents, if needed, now fall easily into place.

 

Two Meters Solution - RF CafeTwo Meters  

The dc ammeter indicates average-current values while the ac ammeter indicates effective or rms-current values. The straight-line graph is used to illustrate their difference. The graph shows a complete cycle of rectangular pulse current in relation to a time base of five 1/300-second intervals. Referring to the figure, the following equation expresses average current, or the dc ammeter reading:

dc ammeter reading = [pulse width] x [peak current] / [total cycle time]

Thus: dc ammeter reading =

(2/300 x 5)/(5/300) = 2 ampere

The ac ammeter reading is determined by finding the square root of the average value of the squares of the current during the time divisions of one cycle. The current values are: 5, 5, 0, 0, and 0; the sum of their squares 50, and the average 10 amperes. The ac ammeter reading is the square root of 10, or 3.162 amperes.

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Webmaster: Kirt Blattenberger,
   BSEE - KB3UON - AMA92498

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 lady's voice announced "You've Got Mail" when a new message arrived...

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