Here is an unusual twist in waveform recognition presented by Radio-Electronics' and Popular Electronics' quizmaster, Robert Balin. If you happen to be a former analog television repairman, then you will probably recognize the answers based on your many years of diagnosing faulty horizontal or vertical sweep circuits. If not, then you might need to strain the "little gray cells" a bit, as Agatha Christie's premier sleuth Hercule Poirot might say. The instructions say to assume that if you choose the horizontal sweep sawtooth to be the errant signal, then assume the vertical sweep sawtooth is correct, and vice versa. Right off the bat, waveform 8 is unique enough to easily identify the sweep that would produce it since only one has two repeating components. Most of the others can be readily deduced, too, by mentally following the x and y points as the "correct" sweep moves across the screen. If I had more time, I would set up my oscilloscope and signal generators to feed the x- and y-axis inputs to prove the associations. That is left as an exercise for the reader ;-) Have fun.

Sawtooth Sticklers

This quiz will show how good you are at associating waveform distortion with the distortion of a circle on a TV screen.

By Robert P. Balin

Sawtooth vertical and horizontal deflection waveforms in your television receiver control the picture's appearance. A sawtooth with a straight slope beginning and ending with the correct amplitude produces a linear sweep. This, in turn, will reproduce a circle, for example, that not only looks perfectly round but is also centered correctly. If the sawtooth is distorted because of defective components, the circle becomes distorted and displaced.

Fortunately, every waveform distortion produces a predictable change in the shape of the circle. A good trouble-shooter can tell what one will look like by looking at the other.

Can you match the distorted waveforms shown by solid lines with the resulting circles they will produce on the TV screen? It is to be assumed that a linear sawtooth (such as that shown by the dotted lines) will produce a normal centered circle on the screen. When the distortion pictured is in the vertical waveform, the horizontal waveform is assumed to be normal. The reverse is also true. In either case, however, video reception (required to produce the circle) is not affected in any way. The deflection waveforms shown can represent either vertical or horizontal waveforms.

The problem: Find the distorted waveform that will produce a circle having the appearance shown. For each circle, there is a corresponding waveform.

Answers are at the bottom of the page.

Quizzes from vintage electronics magazines such as Popular Electronics, Electronics-World, QST, 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.