1947 RCA-Victor 65U Radio-Phono

1947Mar10LifeThis ad appeared 75 years ago today in the March 10, 1947, issue of Life Magazine. It’s for RCA Victor’s model 65U radio-phonograph. It’s a typical “All American Five” broadcast radio with automatic record changer. It has a large elliptical speaker, and it’s a nice sounding radio.

I actually own one of these that I got back into working order a few years ago. The automatic record changer (said to be capable of 12 ten-inch records or 10 twelve-inch records) stopped working a long time ago, but the phonograph still plays manually. The original cartridge was no good, but I substituted a more modern ceramic cartridge, held in place with a piece of foam rubber and rubber bands. The lid can be closed completely while records are playing, a relatively uncommon feature of tabletop sets of that age.



1962 Four Transistor “Half Pocket” Portable

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Sixty years ago, this listener was probably the first on her block to own a transistor radio.  And she was almost certainly the owner of the smallest radio.  Smaller than a pocket set, this one was billed as a “half pocket” portable in the March 1962 issue of Radio Electronics.

The four transistor set measured only 1-11/16 x 1-1/2 x 11/16 inches, with a 2N345 serving as regenerative detector, with three 2N207’s amplifying the audio.  It was “about the size of a petite ladies’ cigarette lighter,” and smaller than some hearing aids.  It was said to pull in local stations with good volume and clarity, and required no external antenna or ground.

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1962 Grocery Prices

1962GroceriesFor a snapshot of grocery prices 60 years ago, this ad appeared in the Arizona Sun on March 8, 1962. There’s been a lot of inflation in that time period, and according to this online inflation calculator, one dollar in 1962 was the equivalent of $9.31 today. So the dozen eggs for 39 cents look like a bargain, but that would be the equivalent of $3.63 in today’s money.

Some items, on the other hand, really were cheaper back then. You could get three pounds of ground beef for 89 cents. That works out to the equivalent of $2.76 per pound.



1947 TV Kit

1947MarPMIf you wanted to be the first on your block to have television 75 years ago, and you were reasonably adept with a screwdriver and soldering iron, then this kit might be just the thing you needed. When you were finished, you would have a set with a 7-inch picture tube, large enough to be viewed comfortably by 10 or more people. You could put it into operation at any locality where television reception was available.

The kit retailed for $159.50, and was geared up especially for schools. All difficult assemblies were prewired, so you didn’t have to worry about getting it into alignment. It cam pre-tuned for three channels of your choice, dictated by which stations were on the area in your area.

While no cabinet was included, it is noted that the 3000 volts were carefully protected by insulation, an interlock switch, and a bottom plate under the chassis. This description appeared in the March 1947 issue of Popular Mechanics.



Prewar Radio Allocation Table

1942MarRadioRetailingFor a snapshot of how the radio spectrum was allocated 80 years ago, this chart appeared in the March 1942 issue of Radio Retailing. You can click on the image above for a full-size image, and on most browsers, click again to enlarge.

While America was now in the war, the allocations above are really the last prewar allocations, as they would have appeared on December 6, 1941. Since then, for example, Amateurs had left the air for the duration. At the time, the amateur bands were on 160, 80, 40, 20, 10, 5, and 2-1/2 meters. Postwar, the allocations would be similar on 160 through 10, with the addition of the 15 meter band a few years after the war. The VHF allocations shifted slightly to 50 and 144 MHz.

With some changes, the TV channels were in their postwar configurations. FM broadcasting would move from the 42-50 MHz band up to its present allocation at 88-108 MHz.



Science Fair Idea: “Lens” for Sound

1937MarPSFor students looking for a simple but impressive (and slightly dangerous) science fair experiment, this one from the March 1937 issue of Popular Science is almost certain to bring home the blue ribbon. It demonstrates that sound waves can be manipulated with a “lens” in the same way that light can. In this case, the “lens” is made up of a balloon filled with carbon dioxide. Since the CO2 is heavier than air, a bubble full of this gas refracts the sound waves. This can be shown, as hear, by using the “lens” to amplify a distant sound. To prove the effect, another balloon filled with normal air can be compared.  If the teacher requires that the project answer a question, then the question can be, “can sound waves be focused in the same way as light waves?”

To generate the carbon dioxide, the method suggested by the magazine is to place some limestone into a bottle containing muriatic acid.  The balloon is placed on the bottle and quickly inflates with the carbon dioxide produced by the reaction.

WARNING: Muriatic acid is another name for hydrochloric acid, and it’s very dangerous. You need to take precautions from getting it on your skin, and especially your eyes, since it could blind you. Do this part of the experiment outside, wear eye protection, and follow these other safety precautions. But you can get the muriatic acid at your local hardware store or on Amazon.  For children too young to handle the acid, a parent or teacher can produce the carbon dioxide and give the balloon to the child. The balloon full of CO2 is perfectly safe.


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1962 Kids’ Table

1962MarPMtableUnless you’ve been living under a rock, you’ve noticed that inflation is once again a thing, and prices of just about everything are skyrocketing. But the kids shouldn’t suffer just because politicians can’t get their act together. And if the kids need a nice table, then you can provide them with one at zero cost.

You simply find a cardboard box of sufficient size. (Before you take it, make sure there’s not another victim of the economy living in it.) With a sharp knife (perhaps the Opinel pocketknife we previously reviewed), you simply cut away everything that doesn’t look like a table, as shown in the self-explanatory illustration.

Your parents and grandparents had a lot of interesting stories about how they had fun during the Great Depression, and now your kids will be able to do the same thing. This idea is from the March 1962 issue of Popular Mechanics.



Laco Kitcraft Model 200 One-Tube Radio, 1947

1947FebPS5LacoKitcraftSeventy-five years ago this month, the February 1947 issue of Popular Science showed this simple one-tube radio kit, the Laco Kitcraft Model 200.  The kit sold for $6, and featured a single 1L4 (or 1T4 or 1U4) tube, and required 1-1/2 volts for the filament, and anywhere from 22-1/2 to 90 volts for the B+.

According to the magazine, it was perfect for the youngster who wanted his or her own radio.



Anemometer With No Moving Parts

1957FebPE10If Junior wants to take home the blue ribbon at the next science fair, this project will almost certainly provide it. When Junior announces to the science teacher that he or she is going to build an anemometer (an instrument for measuring wind speed) with no moving parts, the teacher will be mystified, and will wonder whether it is even possible. But when they see the completed device in action, they will be astonished at its simplicity.

1957FebPE11The anemometer consists of a Wheatstone bridge circuit, which consists of four resistors. Two of the resistors are actually thermistors of equal value. As long as their resistance remains equal, the meter shows a reading of zero. But if they are unequal, then the meter displays a current. The two thermistors are placed outside at the spot where the wind is to be measured. When they are energized, they heat up slightly, which causes their resistance to change. As shown at left, both are mounted in a small plastic container, but one of those containers has small holes drilled in it. When it is exposed to the wind, it is cooled, but the other thermistor is not. The stronger the wind, the greater the cooling, and the current increases. In other words, as the wind increases, it is shown on the meter.

Once the meter is built, it needs to be calibrated, and that requires Junior to “enlist the services of a competent automobile driver” on a “highway which permits maximum state speed limits.” The driver accelerates to 60 MPH, and Junior holds the thermistor assembly out the window, as far as possible. (We note that Junior should take care not to have the arm amputated by a passing truck.) Junior then adjusts the instrument so that it indicates a full scale reading on the meter. The measurement is taken again at different speeds, and the meter reading is noted.

When Junior is awarded the blue ribbon for this elegantly simple design, the teacher will undoubtedly be thinking, “why didn’t I think of that?”

The original construction article, from the February 1957 issue of Popular Electronics, called for a “matched pair” of thermistors, since they need to have equal values. While it might not be possible to buy a matched pair, there is an inexpensive alternative. Junior can buy this set of 100 thermistors on Amazon at a very reasonable price. It includes 10 each of different values, including the needed 2kΩ. Junior just needs to measure all ten, and then use the two that are the closest in value. The remaining 98 thermistors can be used for other experiments. In fact, by adjusting the values of the other resistors, another value of thermistor could be used.

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1937 Two Tube Regen

1937FebPS02Eighty five years ago, the February 1937 issue of Popular Science carried the plans for this two-tube regenerative receiver for the broadcast band up to 65 meters (about 4.6 MHz) with two plug-in coils. The set used two type 49 tubes, with the first one reflexed to serve as both RF and AF amplifier. The second tube served as regenerative detector.

The remarkable part of this receiver was that the B+ was only 11 volts. It used two dry cells for the filaments, which were also hooked in series with a 7.5 volt battery. The magazine noted that this made the receiver ideal for portable use, since the batteries were small enough to be carried in a pocket.

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