Yalta conference. Wikipedia image.
Today marks the 75th anniversary of the conclusion of the Yalta Conference, 4-11 February 1945, at which Roosevelt, Churchill, and Stalin worked out postwar plans for carving up Europe. Roosevelt would be dead two months later, with Harry Truman taking over at the Potsdam Conference that summer.
A hundred years ago this month, the February 1920 issue of Boys’ Life asked the boys of America if they had a wireless station, and offered these two receivers. Both tuned 200 – 2500 meters (120 – 1500 kHz). Each included the loose coupler, radiometer, headphones, and hardware for the antenna and ground. The Moded 4007, selling for 28.00, included a crystal detector. Model 4008 was identical, but used an audion tube for the detector. It sold for $48.
The ad promised that the set could be up and running within hours. The crystal set was said to have a range of 300 miles under ordinary conditions, with the audion set being capable of pulling in stations up to a thousand miles away.
The manufacturer, the A.C. Gilbert Company, is the same one which is famous for erector sets, chemistry sets, and other tools for young scientists. While the company no longer exists, the brand name is still in use. The set in operation here is similar to, or possibly the same, as the one we previously featured, delivered by Santa Claus in 1919.
For the American housewife fighting on the Home Front in 1945, here was the battle plan, as published 75 years ago today in the February 9, 1945, issue of the Pittsburgh Post-Gazette.
One way to compare the spending power in pre-1964 dollars is to remember that one dollar was one silver dollar, which is worth about $18 dollars today. So 25 pounds of flour was 98 cents, which works out to about 70 cents per pound in today’s money. That seems pretty reasonable, but eggs work out to about $10 per dozen, and pork sausage to over $6 per pound, meaning that the housewife had to be creative when it came to getting protein into her family’s diet.
Some items, such as beef, sugar, and butter, were rationed. But all of the items in this ad were freely available.
Shown here, from the February 1945 issue of Radio Craft, is a compact one-tube shortwave set dubbed “The Ultra.” It’s a superregenerative set covering 10-120 meters using a 117ZP7-GT tube. One half of the tube is the rectifier, with the other half serving as the superregenerative detector. The magazine notes that the set features post-war details such as phosphorescent panel marks. These are made from glow-in-the-dark paper coated with calcium sulphide which is carefully applied to the panel. After being exposed to the light, the markings will then glow in the dark with a purple hue.
The set is shown here with a bent antenna, and the author notes that this antenna is sufficient for strong stations. He cautions against use of an outdoor antenna, as the set will radiate and interfere with other nearby receivers. He suggests the use of one stage of RF amplification if an outdoor antenna is used.
One shortcoming of a superregenerative receiver is that it’s practically impossible to listen to code. When the key is down, the receiver is silent, and when the key is up, the receiver is making a loud rushing noise. Since this is the exact opposite of how it should sound, the author acknowledges that this is a shortcoming. But for AM signals, it would appear that this little set would really pull in the stations.
With Canada’s men off to war, it was up to the women to work in war industries, as shown by this ad from the Toronto Daily Star 75 years ago today, February 7, 1945.
The ad doesn’t identify the company, but it’s a well-established organization that manufactures radio tubes. Women were needed full time to work as assemblers, and the work promised to continue after victory.
Application was to be made at an agency located at 832 Bay Street, Toronto.
Sixty years ago this month, the February 1960 issue of Electronics Illustrated carried the plans for this one-tube regenerative shortwave tuner. The article was part 6 in the magazine’s build-it course, and the new tuner was designed to plug into the existing projects, which already included AM and FM tuners. For that reason, this receiver contains no power supply or audio amplifier. The cord with the 8-pin plug was keyed to fit the rest of the project, and the shortwave tuner took the place of the FM tuner.
The circuit used a 6BC5 tube. One notable feature is that the regeneration was taken from the screen grid of the tube, rather than the plate. The regeneration control was a voltage divider which varied the positive voltage to the screen.
Since the article was part of a course, in addition to the exact schematic diagram, it also included a simplified diagram along with an explanation of each part of the circuit. From most browsers, click twice on the image for an enlarged version.
Here is the actual schematic for constructing the receiver:
This little broadcast set looks nondescript, but it was also something of a holy grail. As the February 1950 issue of Radio Electronics put it, “the one-tube loudspeaker receiver has long been the goal of constructors and experimenters.” And this set fits the bill. And as an added bonus, the addition of a single capacitor turned it into an excellent code practice oscillator.
The circuit, using a 3B7 tube, is described as a “special type of utraudion with a certain amount of superregeneration.” An outdoor antenna was recommended, but near powerful stations, the article noted that 25-50 feet were adequate. In remote areas, a hundred feet might be necessary.
The set used a permeanility tuner, which is likely unobtainium. However, the circuit could probably be modified to use a fixed inductor and variable capacitor.
Sixty-five years ago this month, the February 1955 issue of Popular Electronics carried the plans for this CW transmitter especially designed for the Novice. The rig used a single 6AQ5 tube to put out a signal on the 80 or 40 meter bands. Tuning up was accomplished by using a 6 volt bulb attached to a 1-1/4″ loop of wire. This was held near the transmitter’s coil and the rig tuned for maximum brightness.
To keep the circuit as simple as possible (and keep hum producing components at bay), the transmitter did not contain its own power supply. Instead, it required about 250 volts DC at 1 amp. “Most experimenters keep a small power supply of this type on hand for general use.” For those who didn’t, the magazine suggested that they were cheaply available as surplus. For portable use, batteries could even be used.
One interesting feature was the use of an octal tube socket for the crystal socket. The pins were such that a crystal would fit. The unused pins were used as a terminal strip for other components.
Happy Groundhog Day from OneTubeRadio.com! This cartoon appeared 70 years ago today in the February 2, 1950 edition of the Pittsburgh Post Gazette.