Sixty years ago this month, the October 1968 issue of Popular Electronics carried a project, many variations of which have appeared over the years. It’s a “stolen power” receiver.  It consists of two crystal sets, one to tune in the desired station and another to supply power to the one-stage audio amplifier.

The “power” section is tuned to the strongest local station, which provides a DC voltage of a few hundred milliwatts, enough to power the CK721 transistor audio amplifier. The other crystal set tunes in the station, whose audio is amplified for listening.

To operate, a station is tuned in, and the power section is tuned until maximum volume is achieved. This tuning is then left alone.

According to the article, with a good ground and strong enough local station, the set could come to life with just a metal lamp serving as antenna. For optimum reception, a 50-100 foot outdoor antenna was recommended.

The gentleman shown here is putting together one of three circuits built around a 6C8G tube from the October 1938 issue of Popular Science.

The first project was a battery powered receiver which used half of the dual triode as regenerative detector, with the other half serving as audio amplifier. Plug-in coils allowed the set to tune both broadcast and shortwave bands.

The second project used half the tube as a rectifier, allowing the set to be used on AC or DC household current.

According to author author, Clark Maxwell (not to be confused with James Clerk Maxwell of Maxwell’s Equations fame), the set was able to pull in several European stations from New York City.

Finally, the magazine showed how the tube could be used as a two-stage audio amplifier.

Battery operated receiver.

AC-DC Receiver.

Audio amplifier.

A staple for many years in electronics magazines was the ad for the Progressive Edu-Kit, a kit which could be re-built in 15 different configurations. A review of the kit and copy of the manual can be found at this link.

The full-page ad usually appeared on the back cover of the magazine, and as far as I knew, this was the only product ever sold by the company.  But from the ad shown above from the October 1948 issue of Radio Electronics, it appears that the company started out with a more diverse product line.

In addition to the products shown here, the ad from the Progressive Electronics Co., 497 Union Ave., Brooklyn, NY, included a bike radio and car radio.  (The address is now home to the Beer Boutique.)

Shown here is the ad for a combination car radio/battery charger/electric shaver powerizer. In addition to being a 6-tube radio, the set included a battery charger for the car battery. So on cold winter nights, you could plug the car radio into a 117 volt outlet, it would charge the battery all night, and it would “make winter starting sure.”

And if you were running late the next morning, the radio also included an outlet to plug in your electric shaver while you drove to work.

This handy method of determining parallel resistance (or parallel inductance or series capacitance) appeared in QST 75 years ago this month. It was sent in to Hints and Kinks by O.C. Crossland, W9IXV.  All you need is a sheet of lined paper–it doesn’t even need to be graph paper.  You just need to make two vertical lines.

The example shown here computes the value when the two parallel resistors are 6 ohms and 3 ohms.

Today, this would be a simple application of the product over the sum rule.  You would go to the calculator function of your phone and enter (6 x 3) / (6 + 3), and get the answer of 2.

But believe it or not, in 1943, the phones didn’t have built-in calculators.  In fact, they didn’t have calculators at all!  Instead, this graphical method could be used:  You draw a line from 6 on the left scale to the base of the right scale.  Then, draw another line from 3 on the right scale to the base of the left scale.  The point of intersection of the two lines is the answer, 2 ohms.

In 1922, this trio demonstrates that diminutive size of a radio set needn’t mean that the set can’t pull in stations. According to the caption, “how small a set may be, and still be operative over short ranges is shown by the little apparatus that lies on the table.”

The photo appears in Lesson 6 of the seven-part “Easy Course in Home Radio” published in 1922. This group undoubtedly made the parts for their set from scratch, as the photo appears in the lesson entitled “How To Make Your Own Parts.”

The young woman at the right appears to be copying code, meaning that she’s probably receiving the weather report from NAA‘s powerful transmitter in Arlington, Virginia.  Undoubtedly, she donned the headphones since she was the best QRQ operator in the group and wanted to make sure the report was accurately transcribed.

I’m not quite sure what the function of this Soviet electronic project was. It appeared in the magazine Моделист конструктор (Model Designer) issue number 7 of 1968, with the cryptic title “In the air – the coach.” The magazine covers model building, so at first I assumed that it was a radio control transmitter and receiver. But the transmitter appears to be connected to a microphone, and the receiver is connected to an earphone. So it appears to be intended for voice communication, and it appears to be for the 10 meter amateur band. The text mentions “300 – 500 meters,” so I assume that’s the intended range of the set. Elsewhere in the magazine is a discussion of “what is the procedure for registration and operation of amateur receiving and transmitting radio stations.”

In any event, the illustrations speak for themselves, and presumably some young comrades put together this QRP 10 meter AM station. Here’s the schematic and pictorial diagrams of the transmitter:

And here are the schematic and pictorial diagrams of the receiver:

This photo from the October 1968 issue of Radio Electronics shows KIRO Seattle disc jockey Jim French taking a traffic report via CB radio. The article noted that instead of depending on helicopter reports, the station had a network of 40 CB-equipped motorists sending in live reports. The studio and CB antenna were located atop the 600 foot Space Needle. The location ensured a coverage radius of 20 miles, but the QRM was described as unbelievable at times.

Ninety years ago this month, the October 1928 issue of Popular Science tackled the vexing question of whether you should buy or build your radio receiver. The magazine noted that as between building and buying, the magazine championed neither option. It viewed its function as assisting with a wise purchase for those who so desired, or to help solve home construction problems for those who decided to build.

The gentleman shown in the illustration opted to build, and the magazine noted that if you enjoyed working with tools, then assembling your own set would yield good results.

It noted, however, that building a radio was really a misnomer. It was really a matter of assembling factory-built parts.

Either way, the magazine stressed that it was important to identify your needs. Was bringing in distant stations the main appeal, or did you put tone quality first?  By first answering these kinds of questions, the radio consumer would wind up with a suitable set, whether they decided to buy or build.

If you look closely at this picture from the October 1943 issue of Popular Mechanics, you’ll see a 1H5 tube lying on the table. This means that the trio shown here decided to build the one-tube version of the receiver described in the issue. Included were the plans for two almost identical receivers, the difference being that the one shown at left used a crystal detector, while this group decided to tackle the only slightly more complicated,tube version, shown below.

For either set, as long as the builder had a good set of headphones, a quick look at the junk box, or a trip to the dime store, would produce the necessary parts.

Either set was mounted on a 10 x 13-1/2 inch breadboard, with the coil wound on a toilet paper tube. The coils were tapped and hooked to the switch that gave the sets, the Toothbrush Twins, their name. The switch was made with the handle of a toothbrush from which the bristles were removed with a pair of pliers. This was used as the slider, which contacted thumb tacks layed out on the board with the help of a compass.

If a shorter antenna was used, this was fed to the coil. A longer antenna had its own Fahnestock clip, and bypassed the coil.  Either set was said to provide excellent results with local stations, with the tube version showing a bit more selectivity.