Shown here are members of the radio club of William Henry Harrison High School, Evansville, Indiana. The picture appeared in the March 1969 issue of Popular Electronics, which noted that the school claimed to have the only high-school amateur TV station. The club members built the station from modified military and commercial equipment and transmitted with 100 watts on 445 MHz from an 80 foot tower.
The magazine noted that 26 members had general class licenses.
The March 1939 issue of Radio and Television magazine carried this review of the new Hallicrafters Skyrider 5-10 receiver for the “ultra highs,” which at that time meant 25-66 MHz, in two bands, 25-44 and 38-66 MHz.
This, of course, covered the prewar FM band, but the biggest market for the receiver was hams, since the set covered the 10 and 5 meter bands. The set contained nine tubes, including one RF stage and two IF stages. The IF was 1600 kHz, and the second IF tube also served as BFO.
The RF stage was a new UHF tube, the 1852. The reviewer, J. Gordon Taylor, W2JCR, noted that the new tube “really provides respectable gain.” Each stage was separately shielded. To put the new receiver through its paces, the reviewer used it at his home station and at the stations of a number of other New York hams with good 5 and 10 meter equipment. It outperformed all of the existing receivers, with one exception. That exception was the station of W2AMJ, which consisted of a Hallicrafters SX17 with a homebrew 5 meter converter. The review noted that between the receiver and converter, the W2AMJ setup had a total of 15 tubes, as compared to nine with the 5-10. The 5-10 was able to pick up all of the same stations, but the homebrew converter and receiver had greater volume.
Sixty years ago this month, the March 1959 issue of Boys’ Life showed scouts how to put together this two-transistor code practice oscillator. Powered by six penlight cells, one 2N107 transistor served as oscillator, with the other as an audio amplifier. So chances are, the output was both clean and loud. The set featured both tone and volume controls, and had provision for headphones or a built-in speaker.
Seventy years ago was the Goolden Age of Television, as conclusively proven by this article in the March 1949 issue of Popular Science. It details a most interesting program, namely, a live play-by-play of the construction of a shortwave receiver.
Starting from scratch, sound man Rudy Winston (shown at left in the photo) got the set working in 19 minutes while the live cameras of WCBS-TV looked on. The program was 30 minutes, but Winston had only 25 minutes, since the script called for a demonstration. But he was pulling in overseas stations with six minutes to spare.
The feat took place on the station’s “United Nations’ Casebook” program. The purpose was to “dramatize one of the world’s greatest needs–inexpensive, sturdy shortwave receivers.”
Today, inexpensive sturdy shortwave receivers, such as the ones shown below, are readily available. The models shown here can operate from power sources including solar or hand crank, meaning that they can bring shortwave reception to any point on earth. What we need more of are television shows demonstrating how they can be put together.
And, of course, if you get booked to go on TV to build a shortwave receiver, one of these kits will probably allow you to complete it in the course of a half-hour program:
Eighty years ago this month, the March 1939 issue of Radio Craft carried the story of Edward J. Winterding, Jr., of Cleveland. The 21 year old man had been hospitalized for 18 months for some unstated reason. But during that time, he sold nine radios and appliances to hospital staff and other patients.
Seventy-five years ago this month, the March 1944 issue of Radio News reminded readers that they could use a broadcast radio to make sure their 100 kHz crystal calibrator was in tune.
Before the days of digital readouts, you needed to know what frequency you were tuned to. The easiest way to do this was with a crystal calibrator, an oscillator putting out a signal on (usually) 100 kHz. To calibrate your receiver, you would switch on the crystal calibrator, and you would hear the harmonic every 100 kHz up the dial.
To make sure the calibrator was in tune, you could use the method described in this article. You would hook the calibrator up to your broadcast receiver, and then zero-beat it with a broadcast station on a frequency divisible by 100. The article included a list of the 108 stations in the U.S. that met that description. (The article noted that 83 of those stations were on 1400 kHz.
The article noted that FCC rules required broadcast stations to be within 20 cycles of their assigned frequency, although most were closer. It also suggested that a phone call to the station might get a more exact answer as to how close they were at that moment.
Seventy years ago this month, the March 1949 issue of Radio Electronics magazine carried this depiction of the state of television in the United States.
According to the magazine, in the previous year, TV was rampaging across the nation. While a year earlier it had been confined to a handful of cities, it now had a foothold nationwide. 46 million Americans were within range of a station, and the magazine predicted that an additional 25 million would have access before the year was over.
If you’re looking for a really dangerous science experiment, then you need look no further than the March 1969 issue of Popular Electronics. The magazine describes the electret. It points out that it is the analogue of a permanent magnet. Instead of producing a permanent magnetic field, the electret produces a permanent static electric field. For example, it’s possible to make an electret, and then use it to produce a spark weeks, months, or even years later. The name electret was coined by Oliver Heaviside in 1885 as a combination of electr- from electricity, and -et from magnet.
The process to create an electret is quite simple. You simply take a suitable material (in this case, a piece of lucite), heat it to a high temperature, and then let it cool while applying a high voltage. That sounds easy enough, but the voltage must be very high. The article suggests 14,000 volts, and tells you exactly where you can get it–from the family’s portable TV set.
You simply remove the anode clip from the picture tube, and that’s your source of high voltage. But as the article rightly points out, messing around with 14,000 volts could easily prove fatal if you make the smallest mistake. So we don’t recommend this particular experiment. Old TV sets had an interlock for a reason, and that was to prevent them from operating when the case was open. In fact, as the article points out, the wire in question could easily deliver a deadly jolt even with the set unplugged and turned off. This is because the capacitors in the power supply retain a charge. In other words, you probably shouldn’t attempt to duplicate this experiment unless you are very familiar with exactly what the dangers are.
But the procedure itself is quite simple. You build an oven a shown here, and use Sterno to heat it. When you reach the desired temperature, you carefully wire up the high voltage. While standing back many feet, you plug in the TV. If you hear strange noises, then you unplug the TV. Prior to making the connection, and after you unplug the set, you need to discharge the TV’s power supply capacitor. The article recommends an electrician’s glove.
After the lucite is fully cooled, you disconnect things, and you have yourself an electret.
Of course, modern televisions don’t have CRT’s, so they don’t have 14,000 volt power supplies inside. So if you’re intent on duplicating this experiment, you’ll need to find an old TV, the older the better. Even though we have this experiment in the “science fair ideas” category, we don’t recommend it to students due to the lethal voltages involved. But we have many other experiments that you can find by browsing that category.
Alexander Stepanovich Popov. Wikipedia photo.
Today marks the 160th birthday of Alexander Stepanovich Popov, born on March 16, 1859, in Krasnoturinsk, Sverdlovsk Oblast, Russia. He is regarded in Russia and much of Eastern Europe as the inventor of radio. He improved the coherer to the point where it could receive radiotelegraph signals at a reasonable speed. In 1895, he employed the improved coherer as part of a lightning detector. On March 24, 1896, he used radio to transmit a message between university buildings in St. Petersburg.
1989 Soviet stamp showing Povov demonstrating first radio, 1895, Wikipedia image.
Yesterday, we carried a quiz from the March 1969 issue of Popular Electronics. Here are the answers and explanations.
