This ad appeared in Life Magazine 75 years ago today, November 17. 1941. Victor Record recording artist Rose Bampton is listening to records on the RCA Victrola Model V-215 radio-phonograph console.  The nine-tube set provided 12 watts to the 12 inch speaker. In addition to the standard broadcast band, it tuned two shortwave bands, 2.3-6 MHz and 9.3-15 MHz. You can view a nicely preserved example of the set at this link.  The set had an original retail price of $214.95.

As the ad points out, the set features the “Magic Brain” automatic changer, and points out that the Magic Brain does all the work–you just sit back and listen. It also points out that the changer has “no needles,” meaning that it had a sapphire stylus and ceramic cartridge rather than “old-fashioned needles,” and that the total weight of all moving parts on the tone arm was “less than the weight of a postage stamp.”

Mezzo-soprano Rose Bampton performed with the Metropolitan Opera from 1932-1950. She died in 2007 at the age of 99.

This ad for a 5-tube supereheterodyne broadcast radio appeared 75 years ago today in the November 16, 1941, issue of the Pittsburgh Press.

The set sold for $14.95 (complete, no extras), or could be bought on time for a quarter down and fifty cents a week.

The set appears to be model 330, which can be seen at the Radio Attic Archives.  It was a standard “All American Five,” with a tube lineup of 12SA7GT, 12SK7GT, 12SQ7GT, 50L6GT, and 35Z5GT. A schematic and more photos are available at the Radio Museum.  While the set’s tuning range didn’t extend much above the broadcast band, it was billed as easily receiving police calls, as well as distant stations.

Ninety years ago this month, the November 1926 issue of Popular Science showed how to assemble this crystal set for the radio beginner, and offered a number of possible variations depending on the listener’s location and available stations.

The article noted that millions of Americans lived within five miles of powerful stations, but a surprisingly large number had not yet taken an interest in radio. But this simple receiver was billed as a mighty good way to get started, and predicted that many builders would eventually decide to upgrade and build a vacuum tube set. Parts selection kept in mind that many of the components, such as the variable condenser, could be used in the new set.

The author remarked that he had a friend who had a good five-tube set, but kept the old crystal set around for times when he wanted to listen to the radio alone. The headphones masked outside sounds, and he didn’t have to worry about wear and tear on his tubes.

The article suggested modifications of the antenna coil depending on the location and number of stations. It gave instructions on tuning. While moving the dial, you would adjust the crystal for the first hint of sound. When that was found, you would tune the dial for maximum sound, and then adjust the crystal for maximum volume. The crystal position could usually stay put for weeks. To prevent vibrations, the author suggested placing the set on a piece of cloth.

Shown here as it appeared 75 years ago is a view of 100 kW shortwave stations WGEA and WGEO, the General Electric station at Schenectady, New York.  The picture appears in the November 1941 of FM Magazine, along with an extensive look at the technical details of the stations, as well as those of GE’s sister station in San Francisco, KGEI (about which we wrote earlier).

The station had its start in 1925 with an experimental license under the call sign W2XAD. When the FCC deemed shortwave broadcasting to be sufficiently developed for commercial service in 1939, the station went on the air commercially.

GE received over 30,000 pieces of mail per year, and prepared its programs based on listener preferences. In addition to English, the stations had regular programs in Spanish, Portuguese, French, Dutch, Czech, and Chinese.

Frequencies used at the time were 6190, 9530, 9550, 9670, 15330, and 21590 kHz. Directional antennas beamed programs from Schenectady to Central America, Brazil, Europe, Argentina, and North Africa, and from San Francisco to South America and Asia.

One thing that sometimes mystifying when looking at diagrams of early spark transmitters is that the descriptions often lack much detail as to the most important component, the induction coil or spark coil. A good description can be found in Electrical Experimenter magazine, November, 1916, from which this illustration is taken.

The “coil” is really two coils, plus an interrupter, and the operation is described here:

When the primary switch of such a coil is closed, the battery current passes through the first winding on the core and magnetizes it. This attracts the iron armature on the vibrator spring, as shown in Fig. 1, and when this spring breaks contact with the platinum tipped screw in front of it, the circuit is opened. At this juncture there is induced in the secondary winding a very powerful current. The spring-actuated vibrator returns to its former position in the fraction of a second and the process is repeated all over again.

The referenced schematic diagram is shown here: