Monthly Archives: January 2015

1956 Boys’ Life CONELRAD Receiver

BLConelradRadio

In the mid-1950’s, a transistor radio was an expensive luxury. This presented a problem for an impecunious Boy Scout who wanted to Be Prepared for anything. In the words of Boys’ Life magazine for January 1956, “in case of enemy attack, it is assumed that power lines will be down, and battery-operated radios would be a necessity. But batteries wear out. So what you need for Conelrad service is a receiver that doesn’t use B batteries, yet will produce a usable signal when needed.”

The article pointed out that a crystal set might be pressed into service, but wouldn’t produce very loud signals. Fortunately, Boys’ Life had a solution to the problem, in the form of this one transistor set that was well within the construction abilities and budget of a Scout. The set shown here would run on two penlight cells with clear headphone volume for well over a thousand hours. And in a dire emergency, since the set consisted of a crystal detector with one-transistor audio amplifier, the article gave instructions on how to bypass the amplifier and simply use it as a crystal set with reduced volume.

The set is build on a board, with instructions to mount it in a cigar box (painted black, according to the directions), which left ample room for storing the antenna wire, ground lead, and headphones. Since the set was designed for CONELRAD use, the article instructed to find the local broadcast stations closest to 640 and 1240 on the dial, tune them in, and then mark the dial position for future emergency use.

The circuit calls for a FS2500A transistor, which is a general purpose NPN transistor, apparently manufactured by Bogue, also known Germanium Products Corporation.  (See the substitution guide in the 1957 RCA Transistors and Semiconductor Diodes.)

The article was reprinted for a number of years in the Boys’ Life Radio and Signaling reprint booklet. Occasionally, the “Hobby Hows” column of Boys’ Life would answer a letter from a Scout asking where to find the plans for the receiver, who was directed to the reprint booklet. Therefore, I suspect more than a few scouts built one of these receivers, and I’m sure they were put to good use for entertainment purposes. The builders of these sets were undoubtedly the first kids on their block to own a transistor radio. Fortunately, none ever had to be used for the intended purpose of tuning in to CONELRAD alerts.

The author of the article was Howard G. McEntee, W2SI. McEntee was the author of the Radio Control Handbook, published by Gernsback Publications in 1955 and updated over the years.



Operation Cornflakes: Tampering With the Nazi Mail

Forged envelopes and stamps, courtesy of CIA website.

Forged envelopes and stamps, courtesy of CIA website.

Seventy years ago today, January 5, 1945, Allied bombers engaged in an unusual attack. They bombed a mail train heading for Linz, Austria. The train was derailed, and mail was scattered around the area. More bombers then arrived and dropped mail bags appearing for all the world to be genuine Reichspost bags. Inside were about 3800 letters addressed to Germans, many of whom were the families of German soldiers who had been killed in action.

The plan was known as Operation Cornflakes. The return addresses on the letters were those of German firms, and the letters outwardly appeared to be normal business correspondence. However, the envelopes contained propaganda newspapers prepared by the U.S. Office of Strategic Services (OSS), including issues of Das Neue Deutschland, an example of which is shown below.

DasNeueDeutschland

The stamps, envelopes, and even the mail bags, had to be carefully forged to appear original to the postal workers who would handle them. While the program had no discernible effect, it was successful in that most of the propaganda letters were introduced into the German mails. After the train was bombed, German rail and postal workers dutifully picked up the scattered mail bags and sent them onward to their intended recipients.

The stamps and envelopes shown above are examples of some of the forgeries, courtesy of the CIA website. To ensure that the propaganda would blend in with the normal mail, the OSS consulted German POW’s who had worked for the post office. The details of the cancellations had to match what was in use in the cities from which the mail had purportedly originated, and there had to be some semblance of mail being in the proper train for the town for which it was intended. German POW’s provided most of this information relating to the internal workings of the German mails.

Most of the mail was successfully delivered, but in one case, a sharp-eyed German postal worker noticed that the name of the company was misspelled on the return address. This, of course, resulted in that particular batch not being delivered.

References

 

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Wartime 3-Tube Regenerative Receiver

Jan45PMrcvrWartime parts shortages were a major inspiration for the design of this short wave receiver from the January 1945 issue of Popular Mechanics. The lamp isn’t there for decoration; it’s one of the parts.

The receiver used three identical tubes, the 6C5. It ran directly off house current. The three 6-volt filaments are run in series, and to avoid the need for a filament transformer, a 40-watt light bulb in series is used to drop the 110 volt house current to the 18 volts necessary to light the tubes. A standard household receptacle is mounted directly on the chasis, into which a desk lamp can be plugged. Another alternative was to mount the bulb directly on the chasis, using a lamp adapter plug.

Speaking of the chasis, the set is constructed on a literal breadboard, sourced from the nearby dime store. The coil form was also obtained at the dime store, in the form of a plastic drinking cup. The coil is wound with cotton-covered wire, held in place with fingernail polish.

Jan45PMrcvr2The two variable condensers, one for tuning and the other for regeneration, were scavenged from old broadcast receivers. For regeneration, only half of the 350 mF condenser is used. For tuning, the two sections of the 350 mF condenser are wired in series, rather than parallel, resulting in 88 mF, which is better suited to the 25 and 31 meter bands the set tunes. An additional five resistors and five capacitors round out the parts list.

One of the 6C5 tubes is used as a rectifier, one serves as the regenerative detector, and the final one serves as an audio amplifier. In the 1943 Allied Radio catalog, the tubes are available for 56 cents each. The catalog notes that most glass tubes were available in limited quantities. However, it noted that the metal tubes were generally available only to high priority customers.

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Canadian Wartime Nickel Contains Morse Code

The 1943-45 Canadian five cent coin, known as the “Victory Nickel,” is unusual in that it contains Morse Code.  Most Canadians were unaware that they were carrying a Morse message in their pocket, since the code is discernible only upon close examination with a magnifying glass.  It is partially visible on the image shown here.  It’s on the reverse of the coin, and runs clockwise along the edge.  It begins just to the left of the letter “N” in the word “CENTS”.

The beaver design currently appearing on the coin first appeared in 1937, but the coin was redesigned during the war.  The reverse featured the letter V, with a dual significance.  In addition to being the Roman Numeral for five (which was used on the U.S. Liberty nickel from 1883-1912), it was also the symbol of victory.

And with little fanfare, it also included the message, in Morse Code, “WE WIN WHEN WE WORK WILLINGLY.”

The Canadian Mint re-issued the design in 2005, dated 1945-2005, to commemorate the 60th anniversary of the end of the war.  However, the 2005 design did not include the Morse Code inscription.

Specimens of the coin in which the full message is legible are fairly uncommon.  Most were made of steel, plated with nickel.  The sheets were plated before the blanks were cut out, resulting in the edges being unplated.  This has caused most of them to rust around the edges, making the Morse Code illegible.  In the example shown above, the words “WE WHEN WHEN WE” are very legible, but most of the rest of the message is impossible to make out.

The 1943 coin was made of tombac (a brass alloy), and the message is more likely to be legible on specimens from that year.

References

Canadian Mint, Five Cents.

QST, January 1945, page 48.



The First Home Computer, 40 Years Ago

Jan1975PE

The home computer is 40 years old. The one that appeared in January 1975 issue of Popular Electronics. Used copies of this issue typically fetch about a hundred dollars on eBay, but fortunately, a full scan of the issue is available at AmericanRadioHistory.com.  The January issue carried a summary of the computer and some of the construction details. The February issue included an introduction to programming it.

The January issue carried an editorial announcing that the home computer was here. It correctly noted, “for many years, we’ve been reading and hearing about how computers will one day be a household item. Therefore, we’re especially proud to present in this issue the first commercial type of minicomputer project ever published that’s priced within reach of many households–the Altair 8800, with an under-$400 complete kit cost, including cabinet.”

The construction article billed the computer as the “Popular Electronics/MITS Altair 8800.” It was built around an Intel 8080 CPU chip, which could handle up to 78 instructions. The construction article did contain a parts list, but not full PC board templates. Those were available by mail, but it’s likely that most builders took advantage of the computer’s being available in kit form for $397, or fully assembled for $398 from MITS, Inc.

The basic computer came with 256 words of memory, with up to 65,000 being available through add-ons. The parts list called for a 2 MHz crystal, indicating the processor’s speed.

The January article suggested some possible applications for the computer, such as use as a programmable scientific calculator, machine controller, or automatic drafting machine. The February issue included the basics of programming the computer, along with a sample program to add the contents of two of the registers and store them in a third.

Dec1974PETerminalProgramming was accomplished from the spring-loaded switches on the front panel. Another possibility for programming the computer was to use a computer terminal, and the article suggests the design that had appeared in the December 1974 issue, shown here. It’s probably not the mental image that would come to mind upon hearing the phrase “computer terminal.” It’s simply a method of sending an octal code to the computer, and receiving one back.

It was a year or two after the computer first appeared that I first saw one. When I saw it, the builder hadn’t really come up with anything for it to do. He was working on interfacing it with a teletype machine, and at that point, all he could make it do was have it output the character associated with a particular ASCII code. In other words, he entered a number using the front panel switches, and it printed out the corresponding letter. I remember not being too impressed, but I guess I did realize that at some point, I might have a computer in my house.


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Regency TR-1: The First Transistor Radio, 1955

RegencyTR1Sixty years ago, a new phrase entered the American lexicon: transistor radio. Shown here is the first commercially manufactured transistor radio, the Regency TR-1. It was first produced in 1954, and featured here in Popular Mechanics, January 1955.

As shown in the schematic diagram below, the radio used four NPN transistors from Texas Instruments. It was a superheterodyne, with one transistor as the mixer-oscillator, two for IF amplification, and one as an audio amplifier. The detector was a germanium diode. To function at RF frequencies, the transistors required a fairly high voltage, which was supplied by a 22.5 volt battery. (The battery, incidentally, is still available, but it’s now a very specialized item and very expensive.) The radio drew about 4 milliamps, meaning that a battery would last about 20-30 hours. While somewhat expensive to operate, this was an improvement over tube portable radios, which would typically operate for a few hours on a change of batteries.

RegencyTR1Schematic

Texas Instruments produced a prototype transistor radio in 1954, and began shopping around for a radio manufacturer interested in producing it. The major names in radio weren’t interested, but an Indiana company named Industrial Development Engineering Associates (I.D.E.A.) jumped at the opportunity. It was put on the market in November 1954.

Wikipedia photo. "Regency TR-1 opened front Deutsches Museum" by Theoprakt - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

Wikipedia photo. “Regency TR-1 opened front Deutsches Museum” by Theoprakt – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons.

The radio originally retailed for $49.95. To put that price in perspective, coinage of the day was still silver, meaning that the radio could be yours in exchange for 50 silver dollars. Today, that would represent about a thousand dollars. Still, the radio sold about 100,000 units in its first year on the market.

The radio was a generally poor performer. The original TI prototype had included 6 transistors, which was reduced to keep costs down. In particular, the single audio amplifier transistor provided meager volume to the small speaker. Also, it lacked sensitivity, making it suitable only for receiving strong local stations. A review of the radio in Consumer Reports recommended against purchase.

Allied1955PortableFor 1955 listeners who needed a portable radio, a tube set was still the best option.  While they were still bigger in size, the performance of a tube portable would be dramatically better, and the cost would be much lower.  The radio shown here, for example, is a 4-tube portable from the 1955 Allied Radio Catalog.  It sold for $14.95.

Over the years, the price of transistor portables came down dramatically.  The same basic circuit was used in many inexpensive transistor AM radios.  By the time I got one in about 1972, the price was down to $1.99, and that was after inflation.  I believe I owned the exact model shown below, and I remember buying it after seeing a very similar ad in a local newspaper.

Today, specimens of the original Regency in good condition seem to go for about $400 on eBay.

References

 

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Prohibition Comes to Arizona, 1915

One hundred years ago today, prohibition began in Arizona. As the new year began, booze left the recently admitted State of Arizona. The voters had overwhelmingly adopted prohibition in the previous election, and the courts had upheld it only days before. The saloons were busy until midnight, when their trade came to an abrupt halt. Here, we see the headline of this Arizona paper bidding farewell to “John Barleycorn.”

The first arrest took place minutes after midnight, as L.A. Brown, proprietor of the Hermitage, was arrested on the charge of selling “two percent.” He planned to use this arrest as a test case, and he was released on his own recognizance.

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