The concept of a “photo finish” has been around for a century, as shown by this Illustration in the November, 1923, issue of Science and Invention.
This setup was in place at the Maisons-Laffitte Racecourse near Paris. The horses crossing the finish line broke a thread, which would trip the shutter of the cameras above. The photos would be ready in four minutes to decide a close race.
We previously reported the construction, in 1921, of a radiotelephone link between California and Santa Catalina Island, 26 miles across the sea (40 kilometers, for those in leaky old boats). That link was in use for only two years, as reported here in the November 1923 issue of Popular Science.
In 1923, a cable was installed for both telegraph and telephone connections, both of which were multiplexed to allow multiple conversations. One advantage of the new system, alluded to in the original article, was that radio conversations could be listened in to. While some scrambling was put in place, the signals were transmitted over the air. In addition, the radio license was surrendered, and that wavelength made available for broadcasting.
Today, we have another science fair project suitable for students who like to use dangerous chemicals. It’s a homemade photoelectric cell. It won’t provide large amounts of current, but it is measurable, and it can probably be used to receive a signal from a modulated beam of light, simply by connecting it to an audio amplifier (similar to this previous project).
The cell consists of a beaker of water in which a “pinch” of salt has been added. Into this are inserted strips made of copper and lead. The copper is heated with a torch to oxidize it, after which it is scrubbed with nitric acid. There is some current even in darkness, but when the copper strip is exposed to light, the current increases.
The project appeared in the November 1948 issue of Practical Wireless.
The plans for this two-tube British bedside portable appeared 75 years ago this month in the November 1948 issue of Practical Wireless. The set was designed to pull in the BBC Light and Home Service programs with loudspeaker volume, using commonly available components. It ran on battery power, and used two tubes. Because a small frame antenna would be used, the author realized that at least one stage of RF amplification would be necessary. Therefore, the first tube was a dual tube, servicing as RF amplifier and detector. Another tube served as AF amplifier to drive the speaker.
If Junior is looking for a simple science fair project, albeit one that probably can’t be whipped together at 10:00 PM the night before it’s due, he or she can’t go wrong with this simple AC generator from the November 1963 issue of Electronics Illustrated.
The design is very straightforward. To avoid having to worry about brushes, the coil stays stationary, and the permanent magnet turns. The coil consists of 800 turns of number 28 or 30 enameled wire on a 2 or 3 inch iron bolt.
The magazine recommends using a DC ammeter, with the calibration set so that 0 is mid-scale. As the crank is turned slowly, the needle will deflect first one direction, and then the other.
Another possibility would be two LED’s in parallel, each pointing a different direction. As Junior slowly cranks the handle, the lights will alternate, and as the speed picks up, they will both appear lit.
For more projects, some of which can be whipped together at the last minute, browse our other science fair ideas.
If you were looking for radio supplies in Omaha a hundred years ago, the Brandeis department store was the place to go, as shown in this ad in the Omaha Bee, November 24, 1923.
You could get a complete Radiolet crystal set, normally a $10 value, for only $6.95. That included everything you needed to start pulling in stations, since it included the headphones and antenna.
And they knew that the secret of selling radios was to get the kids campaigning for a set. So in addition to their normal radio department on the main floor, they were to be set up in the toy department on Saturday so that the kids could make sure Santa knew the family needed a radio.
Happy Thanksgiving from OneTubeRadio.com!
As you serve your Thanksgiving dinner, you very well might have the radio playing in the background, and, if so, you are part of a century long tradition. This ad, from the October 28, 1923 Washington Sunday Star, for the Lansburgh and Brother Department Store, 420-430 7th St. NW, displays various accoutrements you’ll need for Thanksgiving dinner, such as an electric percolator for only $12.
But the close-up below shows how to really impress your guests. There were sure to be special Thanksgiving broadcasts, and you could entertain your guests with them with a brand new Radiola IV for only $275. It would be a wonderful source of pleasure for your home.
In America 80 years ago, a knock on the door, even when you are listening to the radio, meant that a friend had come to call.
But as this RCA ad in the November 22, 1943, issue of Life magazine reminded readers, things weren’t the same in the Axis countries. It could mean the Gestapo and death if they knocked when you were listening to an American or British broadcast.
In America, you could even listen to enemy propaganda without worry, and it was often good for a hearty laugh. For now, American manufacturers such as RCA were supporting the war effort exclusively. But the ad reminds Americans that they would soon be back with fine radios and other electronic products.
It’s quite possible that the stealth antenna had its genesis a hundred years ago today, as seen from this banner headline in the November 20, 1923, issue of the Washington Times.
According to the newspapers, Washington D.C. radio fans with an outside antenna would need to get a permit from the district engineer office. That permit would need the approval of the District electrical engineer, would require an in-person inspection, and, not unimportantly, a fee of $2 (the equivalent of $36 in 2023 dollars). Since this was the first anyone had heard of such a requirement, the newspaper pointed out that a multitude of radio fans were outlaws.
The order had come down from superintendent of police Daniel Sullivan, who informed the force of the requirement. In no event were the wires to cross any public space. The law had actually been in effect for many years, but the city electrical engineer had only recently brought it to the attention of the police department.
One motivation for the new law was the death of a park police officer while putting up an antenna, presumably on his own time and on his own property. The tragedy apparently prompted the police to begin enforcing the requirement.
Sixty years ago this month, the November 1963 issue of Popular Mechanics showed how to make this 8-in-1 project kit. The heart of the unit was a 2N107 transistor. It could be used as a code oscillator, or with the pitch of the oscillator turned way down, it would start clicking and serve as a metronome. It could also be used as a continuity tester, or for making various alarms.