Monthly Archives: December 2014

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

 

imgHandler

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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Chicago Gets New Fire Boxes, 1864

FireAlarmTelegraph150 years ago today, December 5, 1864, the Chicago Tribune carried this item regarding fire alarm telegraph boxes to be installed in the city. The first was to be installed at the corner of Canal and Polk streets.

One spotting a fire would simply unlock the box, turn the crank, and the alarm would be transmitted to the central station, “unerringly, beyond the possibility of mistake.”

108 such boxes were to be installed. The keys would be given to policemen “and to trustworrthy persons resident nearest the place where the boxes are stationed.” This system, it was said, “cannot fail to vastly diminish the destructiveness of fires in Chicago.”

It’s not known whether such a box was installed in the vicinity of Mrs. O’Leary’s cow seven years later.


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Americans Enlist in Canadian Air Force, 1939

Seventy-five years ago today, December 4, 1939, the Canadian Government announced that U.S. Citizens would be permitted to enlist in the Royal Canadian Air Force. Recruits were required to be of “European descent and resident in Canada.” However, the Canadian government, eager to recruit American aviators, was quite lax on the “residency” requirement. Residency meant only that the applicant must be in Canada at the time he filed his papers.

This, of course, would have been a violation of American law and American neutrality. But even though 9000 Americans eventually enlisted, I’m not aware of a single case of an American being prosecuted for service with the Allies.

The Canadians had even been quietly recruiting in the United States, even though this was clearly a violation of U.S. law. Americans were initially required to pledge his allegiance to the British monarch, which could potentially lead to loss of U.S. citizenship. At some point, however, this was relaxed, and American recruits were required to merely obey RCAF rules and discipline for the duration of the war.

Some Americans had already enlisted. For example, De Peyster Brown, an American pilot who served in the Battle of Britain, had enlisted in the RCAF on September 9, by claiming to be Canadian.

 

References

The Americans in the RCAF