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Mr. E.D. Clark added these three circuit posers to his increasingly large number of "What's Your EQ?" series of columns, this one appearing in the June 1962 issue of Radio-Electronics magazine. While many can be real head-scratchers, the first problem is not too much of a challenge. The resistor and capacitive reactance circuit should also be a piece of cake for even a first-year student. It's a standard voltage divider except you need to account for the phase shift (-90°) of the capacitor, which requires using the magnitude of the series combination. I had to admit that the author's solution to the 1 μs pulse from a 2 μs using only a simple passive device eluded me. I was thinking in terms of an RC differentiating circuit of some sort with phase delays, but a much simpler method is possible. You'll need to think "out of the box" - the spare parts box, that is.

By E. D. Clark

It's stumper time again. Here are three little beauties that will give you a run for the money. They may look simple, but double-check your answers before you say you've solved them. For those that get stuck, or think that it can't be done, see the answers next month. If you've got an interesting or unusual answer send it to us. We are getting so many letters we can't answer individual ones, but we'll print the more interesting solutions (the ones the original authors never thought of). Also, we're in the market for puzzles and will pay \$10 and up for each one accepted. Write EQ Editor, Radio-Electronics, 154 West 14th St., New York, N. Y.

Control Board Problem

A control board monitors five fuel (or water) valves. Each valve actuates an spdt relay (or switch) when closed. The switches light a red light when all valves are open and a green one when all valves are closed. How are the switches wired?

- Arnold A. Paarmam.

What's The Output?

An ac generator supplies current to a voltage divider consisting of a capacitor of 1-ohm reactance and a 1-ohm resistor. What is the output voltage? (This one is, of course, for beginners. Every technician knows the answer - or does he?)

- Bruce Ehrlichanam.

A Shapely Problem

A pulse-shaping circuit requires a positive 1-micro-second pulse to trigger it. The only trigger available is 2 microseconds wide. What is the simplest passive circuit that will reduce the pulse width to 1 microsecond ?

- David M. Nilson

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.

June Solutions

Control-Board Problem

The circuit is as shown. A similar but slightly more complex hookup can be made for an even number of valves, six for instance.

What's the Output?

An ac generator supplies voltage to a voltage divider network, as indicated in Fig. 1. At first glance the output might seem to be 0.5 volt. It is actually roughly 0.7 volt, since ein = √ ec2 + er2. See the vector diagram (Fig. 2).

Shapely Problem

The simplest circuit is a shorted 0.5-microsecond delay line across the shaper input terminals. The 2-microsecond trigger would then be reduced to 1 microsecond as the negative reflection returning from the delay line cancelled the second half of the original pulse. See sketch.

Posted May 22, 2024