We’ve previously written about KGEI, GE’s shortwave station in San Francisco, and the role it played in World War 2. This item 85 years ago today in the February 17, 1941, issue of Broadcasting shows the transmitter building for the 50,000 watt transmitter that would soon be on the air.
The building is still standing, with the KGEI call letter restored, and is used by Silicon Valley Clean Water.
The illustration on the cover of QST 100 years ago this month, February 1926, looks fanciful, but it’s a real scene. The accompanying article contains an actual photograph of the structure, used by Dr. Greenleaf W. Pickard (1877-1956) in carrying out experiments on what we would today call the polarization of radio waves.
Dr. Picard discovered that short waves, unlike long waves, do not remain vertical after leaving the transmitter. The structure was located at Seabrook Beach, NH, and analyzed waves of 80, 40, and 20 meters. Most of the stations received were calling CQ on the ham bands, and a number of schedules were also made. A total of 379 stations were logged to gather the data, including a few Canadian and European stations.
The article concluded by requesting readers to submit reports. It cautioned that a mere list of “calls heard” would be of little use. What was needed was comparisons of vertical vs. horizontal receiving antennas.
Seventy-five years ago this month, these British enthusiasts are operating their radio controlled planes, as shown on the cover of the February 1951 issue of Practical Mechanics.
The magazine carried the first in a series of articles regarding the hobby. It noted that technical expertise in radio was not a prerequisite. Indeed, the author had heard from more than one retailer to the effect that they preferred selling their equipment to those who were not technically inclined. The radio “expert”, it turns out, would often try to tweak the equipment to the point where it wouldn’t work any more.
The article noted that while licenses were required in America, that was not the case in Britain, as long as the users stuck to certain wavelengths. In didn’t specify them, but from the size of the antennas shown, they appear to be VHF.
Seventy-five years ago, the cover of the February 1951 issue of Radio Electronics shows what is recognizable to most pilots and radio enthusiasts as a VOR installation. Apparently, the name VOR (VHF Omni Range) hadn’t caught on yet, as the article uses the term “omnirange”. The Civil Aviation Administration had begun the process of installing them, and the price tag was estimated at a whopping $1.5 billion.
I’ve always thought the VOR was a very clever invention. It allows a pilot, armed with relatively simple passive equipment, to know the exact direction from the ground station. Unlike radio direction finding, there is no 180 degrees of ambiguity. You know right away the exact bearing to the station. This is accomplished by two signals from the VOR. There is an omnidirectional signal, as well as a directional beam that sweeps at a defined rate. By measuring the phase angle between the two incoming signals, the receiver instantly tells your bearing.
The particular station shown on the cover was at Erie, PA, and the photographer was Avery Slack.
We’ve previously reported on projects involving light-beam communication. It’s relatively simple to modulate an electric light, and receive it at a distance.
Fifty years ago, the February 1976 issue of Popular Electronics carried an interesting article by Forest Mims on the same general subject. But this project recreates the work of Alexander Graham Bell in 1880, the photophone. Bell was the first to communicate a voice wirelessly, but his transmitter (and the one shown in this article) is powered only be the sun. It consists of a mirror, to which is glued a short tube into which one can speak. The mirror is mechanically vibrated by the sound.
The receiver is essentially identical to the ones we’ve shown in the past. It consists of a photocell fed into an audio amplifier. With the use of a parabolic mirror at the receiver, or a Fresnel lens, ranges of hundreds or even thousands of feet can be achieved.
Students looking for an interesting science fair project couldn’t go wrong duplicating Bell’s early accomplishment.
When unusual pictures are posted these days, someone is sure to quickly point out, whether or not it’s true, that they are AI. But many of us have honed our healthy skepticism over the years, since it’s long been possible to make misleading photos.
This cartoon illustrating one such possibility appeared sixty years ago this month in the February 1966 issue of Popular Electronics
Seventy years ago this month, the February 1956 issue of Popular Electronics showed how to make this little audio amplifier. The problem of finding a chassis to mount the circuit was solved by using an aluminum battery holder. They were readily available in various sizes, including one for four AA cells. The circuit, using the venerable CK722, used only three volts. Therefore, half the holder was available for mounting the other components, and there were four spare solder lugs that could be pressed into service.
The magazine noted that the circuit would come in handy for things such as amplifying the output of a crystal set.
To avoid favoritism (or maybe that’s just what they happened to have handy), the circuit is shown with one Ray-O-Vac and one Eveready cell.
Eighty-five years ago this month, the February 1941 issue of Popular Science showed how to put together this home recorder, which also doubled as a phonograph. The two-tube (plus rectifier) circuit could be connected to a microphone, or it could tap into the family radio to record programs. In that function, it could also serve the boost the volume of a weak station to play through the speaker.
The only part, of course, which is unobtainium today (along with the blank records) is the recording head.
We were unaware that Pedro, the longtime mascot of Boys’ Life magazine until his retirement in 2022, apparently had his ham ticket, although he had become somewhat inactive in the 1970s. But when he read in Boys’ Life that there was going to be a Scout radio net, he decided to get back on the air, as documented here, in the February 1976 issue of Boys’ Life.
Elsewhere in the magazine, it was noted that the suggested time was 8:00 – 10:00 PM local time on Wednesdays, and 10:00 AM to noon Saturdays on 3940, 7290, and 14290 kHz. Scouts were encouraged to call CQ SCOUT RADIO NET.
Seventy-five years ago, if you wanted to upgrade your television, you could add FM reception, as detailed in the January 1951 issue of Popular Mechanics. As we’ve noted previously, it wasn’t unheard of to swap out the front end of the set and put in a rebuilt tuner. Thanks to Dumont, you could buy a tuner that included, nestled in between channels 6 and 7, the FM broadcast band. As an added bonus, you would probably get a better picture, since the tuner exhibited more gain, especially on the upper channels.
The article explained which models were candidates for the swap.