Category Archives: Radio history

1961 Code Practice Oscillator

1961FebEISixty years ago, the February 1961 issue of Electronics Illustrated showed how to put together this code practice oscillator which is simplicity itself. The article notes “that old headache, acoustical feedback can be useful,” and it’s put to work by simply amplifying the output of a carbon button microphone, and placing the microphone next to the speaker.

According to the article, the placement of the microphone is easier done than described. You basically just move it around until the pitch and volume are right. The author reports that he wound up gluing a poker chip to his to get it just right. The circuit has no volume control, but by reducing the battery voltage, the room-filling volume can be reduced.

The jack on the side is to plug in an external microphone, and use the device as a conventional amp. The article cautions to use a long enough lead in order to avoid feedback in this case, since it’s not wanted.

The choice of speaker and PNP transistors were not critical. The author reports success with a 2N34A, 2N255, 2N256, or 2N554. In this application, a heat sink was not necessary, so the semiconductor could be mounted in any convenient configuration.

1961FebEI2



Stringing the Dial Cord

1946FebNatRadioNewsEven for the electronic genius who is repairing or restoring an old radio, stringing the dial cord is often a vexing problem. It’s a deceptively simple mechanism–you turn the tuning knob, and a string turns the tuning capacitor, and also moves a pointer along the dial. But the devil is in the details–it has to be set up so that a full 180 degree rotation of the variable capacitor results in the dial pointer moving the full length of the dial. Invariably, if you’re not careful, things don’t sync up.

An article in the February-March 1946 issue of National Radio News serves as a good primer on how to do it. The author notes that there are so many variations that even a much longer article wouldn’t cover them all. Fortunately, in most cases, the technician could write to the manufacturer and get a diagram. These days, the dial stringing diagram is often available at the same online sources that carry the schematic diagrams.

If the diagram was not available, the first step was to make a sketch. If the old cord was still in place, the first order of business would be to make an accurate diagram of exactly how it was hooked up.

If the dial cord was already broken or missing, then the first step was to try to figure it out and still draw a diagram. In this case, the diagram would serve two purposes. If the original guess was correct, then it would serve as a guide to do the job. But if it didn’t work, it would document one possibility that didn’t work, thus helping with the process of elimination.

The article cautioned that normal string could not be used for a replacement cord, since it tended to stretch. Instead, the magazine suggested silk or nylon fish cord as one possibility.

Overall, the article serves as a good introduction to the subject, and if you’re faced with this daunting task, I recommend giving it a read before trying to tackle the job.



1941 Four Tube TRF Tuner

1941FebPMEighty years ago, this second period class somewhere in America was getting ready for its radio geography lesson. While the teacher points out western Africa on the map, the audio expert at the back of the room is preparing to cue in a radio lesson on the subject, which will presumably be piped in through speaker number 1 above the map.

He’s pulling in the program on the four-tube tuner described in the February 1941 issue of Popular Mechanics. It’s a TRF tuner which is selective enough to separate the local stations, but has sufficient bandwidth to provide good reception of musical selections. The set can be run through any audio amplifier. In this case, the school is progressive enough to have a public address system installed, and the students will hear the program through it.

1941FebPM2



Postwar Radio Retailing: 1946

1946FebRadioRetailingShown here on the cover of Radio Retailing 75 years ago this month, February 1946, this couple are taking home their first postwar radio. New civilian radios were coming back on the market after a long absence, and there was probably still a shortage, as evidenced by the crowd clamoring behind them.

The magazine reminded dealers, however, that the time would soon come when customers would stop searching for radios. Instead, they would soon be going from store to store choosing. It warned against complacency. Even though it was currently no real task to sell anything, the dealer’s goal should be to make a customer of every shopper. In particular, customers would appreciate a little extra courtesy and consideration.

Selling a scarce item with the same degree of interest that would be called for in a competitive era would have the result of making friends and getting free advertising for his goodwill.

The day would soon come when the dealer would have to fight for every dollar, and attractive selling methods now would go a long way to bring in those dollars.



1951 Crystal Set

1951FebBLSeventy years ago this month, the February 1951 issue of Boys’ Life magazine showed how to put together this simple “non-crystal crystal set”. Regular readers will recognize it was the venerable “foxhole radio,” which used a razor blade and pencil lead for the detector.

The coil is wound on a flat piece of wood, measuring 4 by 2 inches and a quarter inch thick. Paper clips are used for many of the components, such as the slider and connectors.

For ideas on sourcing some of the parts, see our crystal set parts page.



Scouts Listening to the Radio, 1941

1941FebRadioRetailingEighty years ago this month, the February 1941 issue of Radio Retailing showed these Boy Scouts tuning in a program. The magazine reminded dealers that every boy should have a radio in his room, and that this was particularly true for scouts, who needed versatile portable sets for use at home or in the woods.

The Scouts are not identified, other than being from Troop 132 somewhere. The uniforms don’t look quite right for BSA uniforms, and the pennant in the background has the letters “ORIA BC” visible. I’m guessing that it reads “Victoria, BC,” and these are actually Canadian scouts.



Transformer Science Project

 

1946FebBL75 years ago, this young man discovered the secret for meeting girls. That, of course, was explaining to them how transformers worked. This young woman is obviously mesmerized by his explanation.

He gained this skill by conducting the experiment shown below. He constructed his own transformer with two coils of wire wound around an iron core. To provide the alternating current, he runs one wire along the file.

1946FebBL2

These items appeared as part of an for Westinghouse in the February, 1946, issue of Boys’ Life.  It reminded readers to tune in to programs sponsored by the company, John Charles Thomas and Ted Malone.

The science project is easily duplicated today.  While the old-style dry cell battery is no longer available, an alkaline D cell, with suitable holder, would work just fine.  The other items needed are wire, the bulb (with socket to make the connections easier), an iron bar, and file.



1941 Breadboard Crystal Set

1941JanPM3The plans for this crystal set appeared 80 years ago this month in the January 1941 issue of Popular Mechanics. Laying out a circuit in this manner is often called “breadboarding,” and this picture shows why.  The chassis for the set was a literal breadboard.

In addition to serving as a radio, the set could also be used as a piece of test equipment.  It had terminals for incoming AF or RF, and could be used as a signal tracer to troubleshoot other radios.

 

1941JanPM4

Detroit Radio Concerts, 1921

1921JanTalkMachWorld2This photo, in the January 1921 issue of Talking Machine World, shows an early radio broadcast taking place a century ago in Detroit.

The magazine noted that a number of well-to-do residents and members of the Detroit Radio Association were able to tune in radio concerts and dances, furnished by the Edison phonograph, “providing diversion simultaneously in a number of homes, of which some actually are located between four and five miles away.” In some cases, musicians played in unison with the phonograph.

Among the younger set, radio dances had taken a permanent place as a popular pastime, “in the home of those fortunate enough to have had the necessary receiving apparatus installed.”



1961 BSA Radio Gear

1961JanBLSixty years ago, the Boy Scout with an interest in radio could get everything he needed to get started from the BSA National Supply Division at his local official BSA dealer, as shown here in the January 1961 issue of Boys’ Life.

He would very likely be the first on his block to own a transistor radio by putting together one of three kits. The simplest one, which probably required an outdoor antenna, was a fixed diode plus one transistor, which would set him back $4.50. The two transistor model would pull in more stations for $8.95. And everyone would be impressed if he put together the $14.95 three-transistor set, which would give loudspeaker volume.

The beginner could put together the crystal set for only $2.96, complete with cardboard base. And to pull in the shortwaves, the tube set for $15.95 wouild get both broadcast and shortwave.

For code practice, there was a signal set for $1.95 each or $3.95 for two. If the Scout was good at math, he would realize he was paying a nickel more if he bought two, but that’s explained by the fact that it came with 30 feet of wire. And to get started, a code record could be had for $2.95.