Shown here is one of the tools of the trade of the radio serviceman 80 years ago, as shown in the March 1936 issue of Service magazine.
From the Precision Apparatus Corporation, this is the Electonometer Model 500 tube tester.
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This intercom from the March 1943 issue of Radio News shows the kind of ingenuity that was necessary in the face of wartime shortages on the home front.
The article notes that with defense priorities, many small business firms were in need of interoffice communications but unable to get them. The only immediate answer, according to the article, was to make a small radio do double duty.
The article describes a four-station intercom constructed with a six-tube table radio. The only additional parts, all of which were available at the “radio bargain counter” were nine switches, four speakers, and a roll of shielded cable. The hookup allowed for the station with the radio to serve as the master, able to call or receive calls from the other stations. As an added bonus, any of the four remotes could listen to the radio, but stil l make calls.
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Ninety years ago, the March 1926 issue of Popular Mechanics carried the plans for this simple crystal set. The unique twist about this set was how it was tuned. Two metal plates (made from the lids of tin cans) were positioned such that the coil could be slid in and out. To tune the set, you simply slid it to the correct position.
The article noted that the set had selectivity sufficient to tune out a strong station a few miles away. The total cost for the parts was fifty cents.
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I’m a counselor in the Northern Star Council of the Boy Scouts of America for the relatively new Signs, Signals, and Codes Merit Badge. I’ll be doing my first session for this merit badge this weekend, and I put together a collection of various cheat sheets to give the scouts.
If other counselors are interested in having a copy, I have a PDF at my website. Most of this same information is available in the merit badge pamphlet, but not all scouts will have a copy, and it will be helpful to have all of the references in one place.
The merit badge covers a lot of interesting material, and should be of interest to scouts. It’s also one that one counselor cannot adequately handle. I’m an expert on Morse Code, but I’ll be relying on outside experts to help me with subjects such as semaphore and American Sign Language. Many other subjects are also covered, including trail signs, silent scout signals (although “silent scout” is an oxymoron), nautical flags, and even emoticons.
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Seventy years ago, this day’s issue of Life Magazine, March 4, 1946, carried this ad for the RCA model 56X5. The “12,000 Miler” covered standard broadcast and short wave with six tubes, including the rectifier.
I’ve always considered this set to be quite handsome, and it’s also a good performer on both AM and shortwave. A nice example can be found at the Radio Attic Archives. And you can see the set in action pulling in some Chicago stations at YouTube.
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Seventy-five years ago, the March 1941 issue of Radio and Television carried the plans for this two-element 20 meter beam in use by R.M. Blanchard, W4FIC. The antenna was constructed of bamboo, with the driven element and director consisting of wires taped to the bamboo. The rotor consisted of a bicycle chain connected to ropes, adjusted on the ground as shown in the diagram below.
Mr. Blanchard reported that the antenna performed well, logging contacts with the Philipines, Guam, and Little America. In addition, the antenna was used for numerous schedules with the Hawaiian Islands.
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Seventy-five years ago, it was a big month for radio servicemen. The new North American Radio Broadcasting Agreement called for most North American broadcast stations to shift frequencies on March 29, 1941. The trade press was abuzz with how this could be of benefit to servicemen, who would be called upon to reset the pushbuttons of millions of radios.
The undoubtedly caused a bit of trouble for some shops, since resetting the button really required the station to be on the air on the new channel to make sure the job was done right. RCA came out with the piece of equipment shown here, in an ad in the March 1941 issue of Radio Today. For $17.50, the shop could buy the RCA Station Allocator. It consisted of a signal source with several buttons. It would then put out a test signal on the given frequency, making short work of the adjustment of the customer’s set.
More information on this piece of test equipment can be found at RadioMuseum.org. The set was portable, and could run either on AC power or internal batteries, making the house call for this adjustment quite simple.
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Seventy-five years ago, the thrifty radio enthusiast could construct this radio-phono console for only $27.50, following the plans in the March 1941 issue of Popular Science. Even though the set contained only two tubes, it reportedly boasted all of the features of an eight-tube set.
The receiver consisted of a 12B8GT regenerative detector. The article noted that the regeneration control could be left at the same setting throughout the entire broadcast band, without the set breaking into an annoying squeal as the owner tuned from one end of the band to the other.
The amplifier for both radio and phono was a 32L7GT feeding a 6-inch speaker. The dual tube also contained the rectifier, which allowed the transformerless set to run from household power. The filaments were wired in series, along with a 220 ohm resistor.
The $27.50 price tag quoted in the article included everything, including a pre-made cabinet, the phonograph motor, and pickup.
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1908 Leap Year postcard. Wikipedia image.
Today is leap day. In order to accomodate the U.S. presidential election and the Summer Olympics, the years in which those events take place require an extra day, which is added on February 29. These events take place in years evenly divisible by four (2016/4 = 504), and for this reason, Pope Gregory decreed in 1582 that such years would contain 366 days, rather than the typical 365. The first leap year took place in 1584. Even though there was no presidential election or Summer Olympics that year, the new system showed incredible foresight.
The addition of a leap year also keeps the calendar in sync with the Earth’s orbit around the sun, which takes approximately 365-1/4 days. Without the modification to the calendar, the seasons would shift by about one day every four years.
However, the Earth’s period of orbit around the sun is not exactly 365-1/4 days. It is actually slightly more, but because of the effect of the Earth’s precession, it appears from the point of view of an observer on Earth to be slightly less, namely 365.24219879 days.
To get things properly in sync, a few more tweaks had to be made. Therefore, years divisible by 100 (which are divisible by 4, and would normally be leap years) are not leap years. Therefore, 1900 consisted of 365 days, and there was no February 29, 1900.
This correction by itself would make the average year measure 365 + 1/4 – 1/100 = 365.24 days. However, to refine the formula even more, another exception is made. Years divisible by 400 are leap years, even though they are divisible by 100. Therefore, 2000 was a leap year, and there was a February 29, 2000.
With this added factor, the average year length is now 365 + 1/4 – 1/100 + 1/400 = 365.2425 days, which is only 0.0003013 days more than the actual length of the year. This means that it will take 3319 years for the calendar to be off by only a single day. But that seems to be an adequate distance to kick the can, and our descendants can deal with the problem then.
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Just six months after V-J day, Hallicrafters had the S-40 general coverage receiver on the market, as shown by this ad from the February 1946 issue of Radio Craft.
