Category Archives: Radio history

Annexation of Rockall, 1955

Rockall. Wikipedia image.

Today marks the 70th anniversary of what was probably the last time that the British Empire grew. On September 18, 1955, Rockall was annexed by the British Crown. It consists of a piece of granite sticking up 56 feet (17 meters) from the ocean.  I assume it’s named because, well, it’s all rock and nothing else.  You can find it on Google Maps at this link.  If you look at the satellite image, there is a little smudge close to (but not directly at) the pin where Google has it located.

Four sailors were hoisted onto the tiny islet by a helicopter and hoisted the Union Jack. In 1972, the tiny island was made part of Scotland, which is the closest land at about 187 miles (301 km) distant.

The annexation was prompted by a test of Britain’s first guided nuclear missile, which was to take place over the North Atlantic. Since it was supposed that the tiny island might serve as a vantage point for the Soviets to monitor the test, it was important to assert sovereignty.

A fairly large percentage of the visitors to Rockall have been amateur radio operators. While the Island does not have DXCC status, it does constitute an Islands On The Air (IOTA) island. One DXpedition is documented at this link, where it is noted that this was only the sixth time in history that humans had stayed overnight on the island.  Another DXpedition ran into trouble, and it was determined that the best course of action was to make a Mayday call and be rescued by the Royal Coast Guard.



1940 Three Tube Superhet

Eighty five years ago, these hunters are enjoying a radio program while out in the wilderness, thanks to a three-tube superhet shown in the September 1940 issue of Popular Mechanics.

The set was built into a 49 cent overnight bag, and was powered by four flashlight batteries in parallel for the filaments, and two 45 volt batteries for the B+. The B batteries were said to last for nine or ten months.

The tube lineup consisted of a 1A7-GT mixer, followed by a 1A5-GT IF amp, and then a 1D8-GT detector and audio amplifier. A loop antenna was built-in and the efficient circuit supplied satisfactory loudspeaker volume.



1925 One Meter Transmitter

One hundred years ago, the amateur who really wanted to push the frontiers of radio communication might want to experiment with this one-meter (300 MHz) transmitter. It doesn’t appear that the set would be capable of much communication, since there’s no reference to a receiver. Reception is possible locally only with a wavemeter, and this cover photo from the September 1925 issue of The Experimenter shows the set lighting a lamp powered by a nearby resonant circuit.

According to the magazine, transmission with a vacuum tube had been accomplished at wavelengths down to a quarter meter (1200 MHz).



1925 Boys’ Life Crystal Set

One hundred years ago this month, the September 1925 issue of Boys’ Life showed Scouts how to build this radio receiver for a total outlay of $5.52, including headphone and antenna wire. Of course, that works out to over $100 in 2025 dollars, so the Scout would have to be thrifty and save up his money.

While an indoor antenna might work, for best results, an outdoor antenna of 75 feet was called for. The article was penned by Zeh Bouck, who regularly wrote radio articles for the magazine.

The full plans appear here.  You can click on the image below for the full-size version.



1925 Nine Tube Superhet

One hundred years ago, if you wanted a radio that would do it all, you could hardly go wrong with this nine-tube superheterodyne shown in the September 1925 issue of Popular Mechanics. It was equally suited for use at home or as a portable. It weighed in at “only” 50 pounds. The cost was billed as “only” $176.35, but that works out to $3255 in 2025 dollars.

The set, which used nine UV-199 or C-299 tubes, was said to be capable of coast to coast reception, and boasted a built-in speaker.



1965 QRP Transmitter

This ham sixty years ago, probably the article author, Clare Green, W3IKI, at the key of a QRP rig described in the September 1965 issue of Electronics Illustrated.

He notes that anyone can turn on a couple hundred watts and make some contacts. But you could also use the telephone or the U.S. Mail. He discovered the challenge of QRP (low-power operation), and came up with this 1/2 watt transmitter for 80 meters. It was notable for having a stable VFO, meaning that you weren’t stuck on a single frequency.

He notes that the contacts have to be clean on your key, because the low voltages wouldn’t be forgiving of the added resistance.



1965 Wireless Headphones

Sixty years ago this month, the September 1965 issue of Electronics Illustrated showed how to make these wireless headphones, for silent listening without any cord. The audio source you wanted to listen to was fed to a loop of wire going around the room, forming the primary of an audio transformer. The secondary was mounted on the headphones themselves, in the form of a coil wound on a ferrite core.

The one-transistor circuit here could be used with high impedance headphones. For low impedance headphones, a slightly different circuit, with two transistors was shown. As a kid, I experimented with a similar setup, using a telephone pickup coil for the receiver. Some assistive listening systems, such as for hearing aids, or for providing commentary in museums, use a similar system.

 



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Taking the Radio Camping, 1925

A hundred years ago, you could get back to nature, but still be connected to the outside world, thanks to the magic of radio. This group is pulling in a program from their campsite, and appear on the cover of Radio Broadcast magazine, August 1925.



1950 Zenith Cobra-Matic Record Changer

Seventy-five years ago today, the August 28, 1950, issue of Life magazine carried this ad from Zenith announcing the “Cobra-Matic” record changer. A couple of the consoles including it are shown below. “Cobra” is the shape of the tone arm, and “Matic” means that it’s fully automatic.

And it was planned for the future. Who knew what other speeds and sizes of records might show up, so this one was continuously variable for 10 to 80 RPM, to be compatible with all known records, and any that might show up. Record size was also adjustable, so this changer was set for anything.



1945 Emerson Postwar Radios: Model 502

Eighty years ago, production of civilian radios was still banned, but the public and radio manufacturers knew that the end was in sight, and manufacturers were gearing up to meet the pent-up demand. This ad appeared in the Detroit Evening Times, August 26, 1945, and shows what Emerson had planned.

Unlike some similar ads, which were a little bit unclear about what exactly they would be selling, this one hit it pretty close, and featured the 5-tube model shown here. It’s identified in the ad as the model 502.   To make sure you got one of the first, you could go to your local Emerson dealer and place an order.

The set was popular.  My family had an Emerson 503 in the kitchen. This was a more or less identical model, but with a wooden case rather than Catalin. When it stopped working, it was given to me to “fix,” although I wound up simply dismantling it. Many years later, I got another example on eBay, and got it working by replacing the capacitors. Mine is shown here.  (If you look carefully, you can see the dial light, as it was playing when I took this picture.  Like most AA5’s, it’s a pretty good receiver.