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Minneapolis School A-V Equipment of the 1960’s and 1970’s

SetchellCarlsonTV

If you went to school in Minneapolis in the 1970’s, I bet these pictures look vaguely familiar. This is a 1972 ad from Setchell-Carlson, then known as SC Electronics, Inc., a subsidiary of Audiotronics Corporation, with an address of 530 5th Avenue NW, New Brighton, MN. This ad appears in the March 1972 issue of Broadcast Engineering.

The Minneapolis Public Schools were equipped with what I believe was the model at the left.  I’m showing the one on the right to show the distinctive controls in the center, which are hidden behind the optional “tamper-proof control compartment door” of the black and white model on the left.  I don’t think that Minneapolis had the door, or else the doors were routinely left open.

At Waite Park Elementary School, I don’t believe that every classroom was equipped with a TV.  There were one or two of these that were wheeled in as needed.

AV750Every room, as far as I can recall, was equipped with a radio, although it was rarely used.  The radio, shown here, was the Newcomb Model AV-750.  This was an 8-tube AM FM receiver, and was obviously built for severe service.   I’m sure I’m the only kid who noticed, but it had a connection on the back for an external AM antenna and ground.  I was always jealous of that radio, since I dreamed of all the exotic broadcast band stations it would pull in if connected to an external antenna.  There was also a connection on back for audio input, so it could be used as an audio amplifier.

I’m not positive, but I believe this Audiotronics phonograph was the standard issue model in the Minneapolis schools.  Again, I believe one was issued to each classroom, and they saw a bit more use than the radio.

The televisions were made not far from the school.  Setchell-Carlson made some consumer radios in the 1940’s, and TV‘s in the 1950’s and 1960’s.  They were never a big name nationally, although they did have a strong presence in their home state of Minnesota.  By the 1970’s, they had abandoned the consumer market, but they continued to make the institutional models shown above.

There’s a good history of the company in the October 2008 issue of Radio Age.

bc1206

Photo courtesy of Ian O’Toole, VK2ZIO, Kurrajong Radio Museum. Used by permission.

The company was founded in St. Paul in 1928 by Bart Setchell and Carl Donald Carlson as “Karadio Corporation.” As the name suggests, the company manufactured auto radios. Setchell claimed later to have been the “first” to use vibrators to power the car radio. The author of this article disputes that claim, but it is clear that Setchell-Carlson was one of the pioneers. In 1934, the company became Setchell Carlson, Inc., and made a few radios before the war. During World War II, the company was a defense contractor, and made products for the military, the most famous of which was the aviation receiver shown here. (For more information on this device, see my earlier post.)

In 1949, the company moved to New Brighton,

A Setchell Carlson TV from 1954, back when people apparently dressed up to watch TV. Popular Mechanics, Dec. 1954

A Setchell Carlson TV from 1954, back when people apparently dressed up to watch TV. Popular Mechanics, Dec. 1954

Minnesota, and went into the TV business, which lasted until the 1960’s. At its peak, the company employed about 500, and also had a plant in Arden Hills.  Setchell was later inducted into the Minnesota Broadcasting Hall of Fame.

One final note on the audio-visual equipment in use at my elementary school.  The Minnesota Historical Society has this photo  of the school’s public address system.  The photo is dated about 1955, but based upon the one or two times I saw it, this is the same console that was in use in the 1960’s and 1970’s when I was a student there.  Interestingly, the caption of this photo bills it as a “school broadcasting lab” and shows students at the mike.  I never recall the console being used by students, certainly not on a routine basis.

The couple of times I saw this, I was quite impressed.  It was in a separate room off the office, and in addition to the PA console, there was a radio receiver.  I remember one dial being for the standard AM band.  The other dial was calibrated in some numbers that did not look at all familiar to me.  In retrospect, it’s possible that they were FM channel numbers, which were used for a short time on some FM receivers.
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Beaver Baby Grand Crystal Set, 1924

BeaverBabyGrandCrystalSet

Presumably, by 1924, most readers of Popular Radio magazine already owned a radio receiver, and judging from the articles and ads in the December 1924 issue, most of those readers already owned a set with one or more tubes.

This probably presented a marketing challenge for the Beaver Machine & Tool Co. of Newark, N.J., maker of, among other things, crystal sets. Since it was the Christmas season, the crystal set was promoted as a gift item. The company advertised its “Baby Grand” crystal set as a way to “spread X’mas joy by giving these efficient little sets to friends less fortunate than yourself.” The ad assured that the set was “not a junky toy, but a handsomely built instrument” that was ideal for invalids or youngsters. It reported that the set would give satisfactory reception up to 25 miles.

The set was available in a handsome gift box, with headphones, for $6. The set by itself, without headphones, sold for $3.40.

From the number of surviving examples, it appears that the radio indeed not a junky toy. Quite a few specimens can be found through a Google Images search.

The Beaver Machine & Tool Co. does not appear to survive today. Its address is what appears to be a residential section of Newark, and there’s no record of the company. At the time of this ad, however, it was involved in a patent infrignement suit regarding electrical switches. It had been sued by Cutler Hammer for infringement of two patents. Beaver got a belated Christmas present on January 5, 1925, when the U.S. Second Circuit Court of Appeals held the two patents invalid.

 


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1934 Pocket Short Wave Receiver

OneTubePocketSet

80 Years ago, the cover of the December, 1934, issue of Short Wave Craft featured this pocket portable one-tube superregenerative receiver covering the 49 meter shortwave broadcast band. According to the article, the receiver was able to pull in Europe without an antenna. And when tested with a short antenna in the magazine’s offices in a steel frame building in New York, the set picked up “stations galore.” The article notes that the receiver’s superregenerative circuit had one serious drawback: It radiates a very strong signal. The article therefore recommended that “it be operated only in the less congested areas where there are few short-wave receivers and where the danger of interfering with others is nil.” In other words, this particular circuit probably wouldn’t pass muster under Part 15 of the current FCC rules as an incidental radiator.

The author of the article is George W. Shuart, W2AMN, later W4AMN. He also wrote several articles for QST in the late 1930’s through the 1960’s.  His last contribution to QST appears to be a “Hints and Kinks” item in August 1978 for a CW filter.  A 1946 QST article includes a biography which notes that Shuart had been licensed since 1928, and had written numerous articles for beginners, a result of which was that many amateurs got their start from his articles. It also revealed that Shuart was employed by Hammarlund as its Advertising and Sales Promotion Manager. He was the author of the 1937 Radio Amateur Course
published by the same magazine in which appeared this one-tube radio.

The 1934 article provides two possible solutions for carrying the batteries for this pocket radio. The filaments run on two penlight cells, and the B battery can be as low as 22-1/2 volts. One solution is to make the B battery out of penlight cells bundled together and carried in a pocket. The other alternative is to mount them on a strap “which forms a belt that can be worn around the waist. This is an old stunt used in stage tricks.” A picture of this arrangement is shown in the article, and I would advise against wearing this type of battery while visiting an airport.


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1924 Monodyne One Tube Radio

Monodyne

This one tube radio is shown in an ad from 90 years ago, from the December 1924 issue of Radio News.  The ad for the National Airphone Corporation features the Monodyne, billed as “one of the most radical advances in Radio engineering. Parts heretofore considered essential are omitted with no loss of efficiency.” One customer reported hearing a broadcast from over a thousand miles away “like talking over the back fence.” It sold for $10, without the tube, headphones, or battery.

I haven’t been able to find any schematic or other details about this little radio. gifarmer.com has some information, including a photo of a nice surviving example. The radio came with two coils, one to cover 150 to 400 meters, and the other to cover 500-1000 meters. That works out to 750 kHz through 2 MHz, and 300 to 600 kHz. Presumably, those band edges were not exact, since there were stations between 400 and 500 meters, such as WLW on 423 meters (710 kHz) and WMAQ on 448 meters (670 kHz).


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American-Made Plane En Route to England, 1939

PlaneCrossingBorder1939 Life Magazine 75 years ago, December 11, 1939, shows this photo of an aircraft being exported from the United States en route to its new owner, the British Royal Air Force. American neutrality prevented either American or Canadian pilots from flying military aircraft across the border. To remedy this difficulty, the planes were flown from the factory in California to Sweetgrass, Montana. From the airstrip near the border, the planes were towed by automobile over the border. The line running up the picture is the international boundary. The plane’s nose is in Canada, and its tail is in the United States.

The airport in question is truly an international airport. Coutts/Ross Sweetgrass International Airport‘s current runway, 07-26, is a 2900 foot grass strip that runs East-West along the international border. It can currently be used to clear customs entering either the United States or Canada.


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Give Junior a Slide Rule for Christmas!

MathcraftFifty years ago, I bet Santa could barely keep up with the demand from kids clamoring for one of these under the tree. The Mathcraft Set included a slide rule, abacus, protractor, compass, and more. This kid sure looks excited to have one. Or maybe he’s wishing that Santa had brought the bug collecting kit, the weather station, or the chemical lab. All of these and more were featured in Popular Mechanics, December 1964, as good gift ideas for future scientists.

Seriously, though, the slide rule did get us to the moon.  If you want to play around with a virtual one, here are free slide rules that you can use on your Android device:

The real article, on the other hand, is getting hard to find. If you’re not careful with your Amazon search, you might wind up with one of these:


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The LFR: 1920’s-1960’s Air Navigation

From the late 1920’s until the 1960’s, an important tool for air navigation was the Low Frequency Radio Range (LFR).

At its peak, there were about 400 LFR beacons in the United States, and many more worldwide. Each station consisted of a transmitter being fed into two directional antennas. One antenna was sending the Morse letter “A”, dot dash. The other antenna was sending the letter “N”, dash dot. The two signals were synchronized so that the two signals alternated. At four directions from the station, the two signals blended to produce a constant tone. If a plane was off this course in one direction, the pilot would hear the “A” start to get stronger. Off course in the other direction, the “N” would get stronger.

Aeronautical charts such as the one shown here would show the letter that would be heard in each of the four quadrants. Here, in the quadrants south and north of the station, the pilot would hear the letter “N”. In the east and west quadrants, he would hear the letter “A”. On the shaded lines, the pilot would hear the continuous signal. These “beams” would be about a half block wide near the station, and as much as several miles wide far from the station. Most air navigation followed routes along these beams. The course a pilot followed would be along airways connecting the stations, and flying cross country would be a game of “connect the dots” as the pilot flew from one station to the other.

Every thirty seconds, the “A-N” signal would be replaced with the call letters of the station, in this case, RL, which would also be transmitted in Morse.

Despite the simplicity of the system, the accuracy was enough to use for instrument landings, and instrument approaches using the LFR beacons were published for many airports.

For the pilot, only a normal radio receiver was required. In later years, more sophisticated receivers were employed, which would show the pilot visually whether he was on the “A” side or the “N” side of the beam. But in most cases, the pilot navigated by listening to the signal in his headphones.

LFR station using Adcock antenna (Wikipedia photo).

LFR station using Adcock antenna (Wikipedia photo).

Most of the stations operated between 190 and 535 kHz, with powers of up to 1500 watts. Early stations used crossed loop antennas, but Adcock antennas (phased verticals) were used in most later stations.

Directly above the station, there was an inverted “cone of silence” where the directional signal disappeared. Even in times of no visibility, the pilot would know that he had passed over the beacon when the signal disappeared.

Starting in the late 1940’s, the LFR began to be replaced by the VHF Omni Range (VOR). While the VOR required a special receiver in the aircraft, it was superior in that it could be used to “fly a beam” in any direction from the VOR station, rather than just the four possible with the LFR.

bc1206

Photo courtesy of Ian O’Toole, VK2ZIO, Kurrajong Radio Museum. Used by permission.

Shown here is a BC-1206C Range Receiver, which would have been installed in the aircraft for the purpose of receiving the beacons. This radio, manufactured by Setchell Carlson, Inc., of St. Paul, Minnesota, is a five-tube superheterodyne.  As you can see from the schematic, it’s not much different from a standard broadcast receiver.

REFERENCES

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War QRM A Hundred Years Ago

QRM

A hundred years ago today probably marks one of the first times that QRM (radio interference) made the editorial cartoon pages.  This example, from the Richmond Times-Dispatch, December 8, 1914, depicts the interference to U.S. commercial stations from the warships patrolling just outside the U.S. coast.  The signals from the British ships were the primary culprits in causing interference to U.S. stations.


Radio Coverage of Pearl Harbor

 

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USS Shaw at Pearl Harbor. Defense Department Photo.

Contrary to popular belief, the networks never broke into live programming to announcing the attack on Pearl Harbor on December 7, 1941. The first broadcast announcement came at about 2:30 Eastern Time on CBS, during a scheduled newscast.

But you tell me that you’ve heard an announcement breaking into a symphony mid-note, with the words: “We interrupt this program to bring you a special news bulletin. The Japanese have attacked Pearl Harbor, Hawaii by air.” This was actually from a record produced by CBS in 1948. The second sentence came from an actual broadcast later in the day. You can hear the original at this link.

There was apparently no recording made of the first announcement, and there was apparently no interruption of regular programming.

A recording from Minneapolis CBS station WCCO  is available at RadioTapes.com.  While there’s no time stated on the WCCO recording, this was apparently recording during the break in the New York Philharmonic concert, which started at 3:00 Eastern Time.  Therefore, the WCCO recording probably starts at about 3:30 Eastern Time.

References

 



Victrolas for Christmas, 1914

1914OmahaPhonographs

In 1914, Santa Claus probably delivered quite a few new phonographs to American parlors. He had quite a selection available, as shown in the December 6, 1914, advertisement in the Omaha Daily Bee.

Prices ranged from $18.75 to $207.50, with all of them available on credit. The less expensive models could be brought home for $5 down, including a set of records.


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