Happy Valentine’s Day from OneTubeRadio.com!
These girls are pulling in some program on this three-tube receiver, which appeared on this Valentine’s Day card, which I suspect dates to the 1930s. I found it on flickr, where it was posted by user EmilySue.
This gentleman has found marital bliss, thanks to a personal radio receiver he put together according to the plans in the February 1946 issue of Popular Science.
As the magazine pointed out, “instead of thinking harsh thoughts about members of your family who frown on your radio listening when they want to read or sleep, try one of these compact personal radios that make the entertainment of the airwaves your private business.” The wife is undoubtedly in that category, but he made the radio his private business by listening with headphones while she slumbers in peace. Presumably, there were harsh thoughts prior to making this set, and it probably saved the marriage.
The circuit is a three-tube regenerative set. One tube serves as a rectifier to supply the B+ voltage in the AC-DC “hot chassis” design. To run the filaments, multiple “curtain burner” line cords, adding up to 600 ohms are used. While the set is designed for headphones, it’s powerful enough to drive a speaker, and the optional hookup for a speaker is shown.
Sixty 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.
Even 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.
Eighty 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.
Yerkes Observatory. Wikipedia image.
On this day 75 years ago, persons on Earth were able to witness a star going nova. In particular, the star T Coronae Borealis went from being a 10th magnitude star, barely visible with binoculars, to a magnitude 3.0. There were still 120 objects in the sky that were brighter, but for a few days, it was visible to the naked eye on February 9, 1946.
This news account appeared in the Pittsburgh Press, February 9, 1946. It reported that the “atomic explosion millions of times more powerful than the bombs which hit Japan” was first observed by Arman Deutch of the University of Chicago Department of Astronomy at the Yerkes Observatory in Williams Bay, Wisconsin.
The star is a recurring nova. It’s actually a binary system containing a large cool component and a smaller hot component. The cool component, a red giant, is transferring material to the hot white dwarf component. During outbursts, the transfer of material increases, thus increasing the overall luminosity.
The star had a brightening in 2016, which is said to be similar to a 1938 brightening that preceded the 1946 outburst. It is said to remain at an unusually high level of activity.
Shown 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.
Seventy 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.
Eighty 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.
75 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.
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.