1948 Magnetic Recording

The drama student shown above appeared on the cover of the February 1948 issue of Radio News. The young thespian was an early adopter of magnetic recording technology, one of the many civilian technological advances that came from wartime industry. She used a wire recorder from Webster-Chicago Corp. to practice her diction and delivery.

Of course, home sound recording had been possible for some time, thanks to disc records such as the Recordio. But magnetic recording media had the great advantage of being reusable.

The magazine contained a number of features, and it does contain a very complete look at the state of the art in 1948. The two competing formats were wire and tape. Wire held a slight lead in fidelity, but tape was easier to work with, especially when it came to editing and splicing. Interestingly, the magnetic recording tape of the time was actually paper tape with a thin magnetic coating. Typical speed was 8 inches per second.

Among the features of the issue was a construction article for the tape recorder shown here. The project was said to be “well within the capabilities of anyone who has a working knowledge of electronic circuits and who has ordinary mechanical ability.” The mechanical ability was important, because all of the parts had to be made. A metalworking lathe was required, although the article noted that those without one could have the parts custom made at a local shop at low cost. As one of the mechanical diagrams shown at right shows, the construction did require some mechanical skill. Apparently, 75 years ago, that level of skill was ordinary.

The recording/playback and erase heads also had to be homemade, and consisted of a coil wound on a laminated core and placed in a shielded enclosure with just a small opening for the tape. The choice of material for the core was critical, and had to be permalloy. The type of material normally used for transformer cores would not work. The best solution was to buy a particular type of audio transformer, disassemble it, and use the lamination material for winding the heads.

Back Seat Earphones: 1963

Sixty years ago this month, the February 1963 issue of Popular Mechanics carried this project designed to help parents of “youngsters who insist on raucous music and clatter from the car radio throughout a long trip.”

The solution to domestic tranquility was to let them listen to their heart’s content in the back seat, but through earphones. Then, “only plugged ears need hear the racket.”

The magazine showed how to make this small control box, which allowed switching from the car speaker to the headphones. It also included a volume control, in the form of a 20 ohm fader. Installation was easiest if the speaker were mounted on the rear shelf, and the work could easily be done through the trunk. If the only speaker were in the front, the job was only slightly more complicated, and required running two wires under the carpet.

With this modification in place, the rest of the family was guaranteed to be happy.

Amboy Lighting Company, 1923

If you needed radio supplies in the Garden State a hundred years ago, then the place to go was Amboy Lighting Company, 193-195 Smith Street, Perth Amboy, NJ, was the place to go.

According to this ad in the Perth Amboy Evening News, February 9, 1923, the store featured Atwater-Kent receivers, and had just received a shipment of Federal headphones.

1953 Hi-Fi Amplifier

Seventy years ago, this young woman was tasked with providing the high fidelity audio system for some important event, and she carried out the assignment by constructing this high-power low-distortion amplifier from the February 1953 issue of Popular Mechanics.

The amplifier, suitable for use with any high-quality speaker system, put out a respectable twenty watts with two 6L6’s running push-pull, with only 5% intermodulation distortion (IMD). At ten watts, the IMD was well under 1%.

The set boasted seven tubes, including rectifier, and as shown here, it was easily portable.

Nighttime Radio: 1923

A hundred years ago, radio was clearly a nighttime activity, as shown by this hapless radio buff on the cover of Radio News, February 1923. Hams were still mostly playing around with the medium frequencies just above the standard broadcast band. They didn’t know what the D layer of the ionosphere was, or that it was absorbing their signals as soon as the sun came up. What they did know was that their signals got out at night, but could communicate only locally by day.

So they worked the radio by night, and took care of other less essential activities (such as work and sleep) by day. It wasn’t until they started getting pushed up into the “useless” short waves that they realized that those frequencies promised world-wide communications by day or night.

Women in Radio, 1943

Eighty years ago this month, the February 1943 issue of Radio Retailing acknowledged that there had long been prejudice against women in the field of radio servicing. But the exigencies of war meant that the industry no longer had time for that luxury. Just as the armed services were incorporating women into their ranks, private industry was going to need to do the same thing. There was a war to be won, the men were overseas, and this meant that women would need to prove once and for all that they were capable of doing the work.

According to the magazine, “often we think of women as stenographers, clerks, small parts assemblers, and light machine operators. But that is no longer the case. Women are moving into the ranks of engineers, chemists, draftsmen and other technical and professional activities, as well as into any and every other occupation that once was reserved to men.” Just as there was a women’s corps in the armed services, the magazine stressed the need for a Women’s Corps for the Radio Store.

In hiring anyone, male or female, long experience was not required, but merely the proper training. And that training, more often than not, could take the form of friendly personal supervision, along with a free hand to exercise their natural talent for neatness and order.

The magazine concluded by noting that “women have made good in every occupation they have tackled, though it cannot be said that all employers have given women the same thoughtful selection, and training they have to men.”

Happy Groundhog Day!

Happy Groundhog Day from OneTubeRadio.com!

If your car’s transmission is giving you problems today, perhaps it’s as explained in Gasoline Alley this day a hundred years ago. The image here is taken from the February 2, 1923, issue of the Casper (Wyoming) Daily Tribune.

Radio Facsimile: 1938

Eighty five years ago, they didn’t know it wasn’t going to catch on, but it looked like the next big thing was going to be facsimile. The January 1938 issue of Radio Retailing carried a feature discussing the state of the art. It acknowledged that television was right around the corner (and it was, with only a world war serving to delay it), but the magazine incorrectly predicted that facsimile equipment might find its way into American homes before television.

The idea seemed reasonable, since a number of stations were already licensed to send fax transmissions, as shown by the list at the right. In the Upper Midwest, both WHO Des Moines and KSTP Kansas City held licenses to broadcast with the new mode, on their standard broadcast frequencies.

The magazine acknowledged that standards had to be fixed before facsimile service became common. And testing needed to be done to see how well it worked in outlying areas. And it still wasn’t know if the receivers would be standalone units, or if a printer would plug into the loudspeaker output of a standard broadcast radio.

Shown above is a pioneer of facsimile transmission, W.G.H. Finch of Finch Telecommunications, Inc. Other contenders for a market share were R.C.A., Radio Pictures, and Fultograph. Facsimile service was seen as a way in which radio stations could take on the competition of newspapers. But when the War ended, television took off a lot faster than many people imagined, and radio facsimile service is relegated to a footnote in the history of radio.

Winter Field Day 2023 – QCX Mini Review

This weekend was Winter Field Day, an event in which amateur radio operators set up at a remote location and see how many contacts they can make. Two years ago, many hams stayed home in the mistaken belief that being in a field somehow causes COVID. To dispel that notion, I set up at a state park campground, where I operated while socially distancing myself hundreds of feet from other persons.

Last year, I operated a little bit from home, albeit with battery power, and doing my best to work only portable stations. But the name of the event is Field Day, and it doesn’t make a lot of sense to do it anywhere but out in the field. Santa Claus recently gave me a new QRP (low power) radio, the QCX Mini for 40 meters, and this was a good opportunity to put it to work.

Review of QCX Mini

QRP Labs image.

I’ve had the QCX Mini, a product of QRP Labs, a few weeks now, and I’m absolutely amazed at how well this radio works. It weighs less than half a pound, and can easily be held in the palm of your hand. It’s available for multiple bands, but I chose 40 meters, which is almost always open to somewhere, day or night. Winter Field Day is, in addition to being a fun activity, an exercise in emergency preparedness, and this tiny rig is one that you could carry with you anywhere. You just need to plug it into a key, headphones, power supply, and antenna. It’s an excellent CW transceiver, and in many ways, it’s comparable with even the best stations.

The receiver is possibly a little less sensitive than a full-size receiver at home, but it’s more than adequate for QRP use. My best DX with it so far was Austria, I was able to pull in the other station’s signal, and he was able to hear me. Additional sensitivity wouldn’t really add much.

It is, however, extremely selective, and has a narrow filter which is ideal for CW. The downside is that the filter is an analog filter permanently wired in, so it’s really not possible to copy AM or SSB signals. You can hear them, and make them out to some extent, but not very well. For example, the receiver is able to tune to both 5 and 10 MHz, and I can hear the beeps from WWV, but can’t really copy the voice messages.

In addition to the transmitter and receiver, the little radio has a built-in keyer, and even a code reader. The code reader doesn’t work quite as well as the one between my ears, but it actually does come in handy. Occasionally, I might miss a letter, but there it is, right on the screen. And if I forget a call sign before writing it down, it’s there on the screen for a few seconds until it scrolls away.

I haven’t tried it out yet, but the QCX Mini also contains a WSPR beacon that might be fun to play with. You can read the QST review of the radio at this link.

If someone wants to get into amateur radio very cheaply, and they’re willing to learn Morse Code, the QCX Mini would be a very inexpensive way to start. Completely assembled, it sells for about $120. Of course, knowledge of Morse code is necessary, but the code reader makes the learning curve a bit easier. As long as the station you’re working is sending reasonably good code, the built-in reader will help you catch all or most of what you might have missed. Even if you’re a little unsure of your abilities at first, you can get on the air right away, and build your speed up on the air, rather than having to worry about “practicing.”

In kit form, the radio is only $55, although you probably want to spend an additional $20 for the case. (But it would work fine with the printed circuit boards exposed.) If you get the models for 80, 40, or 15 meters, only a technician class license is required, and that can be done with a weekend of study (perhaps using the study guide I authored).

Winter Field Day Summary

The contest incentivizes operating away from home, so I decided to trek a bit further than my own back yard. I toyed with the idea of just sitting in a folding chair outside, but the temperature was only 5 degrees Fahrenheit, so I opted to sit inside the car for a little protection from the elements. I found an almost-empty parking lot at Como Park in St. Paul, MN, and decided to operate for a couple of hours from there.

The 40 meter band is best during nighttime hours, but I wanted to avoid sitting in the dark as much as possible. So I arrived at about 4:00 PM local time, and stayed until a little after 6:00. Most of my time there was in daylight, but with very good band conditions.

My antenna was an inverted-vee dipole. The center was held up with my trusty golf ball retriever shoved into a snowbank next to the car, and the ends were tied to the ground. Normally, I just pick up a stick off the ground and use that as a stake, but when I got there, I realized that all of the sticks were buried under two feet of snow. A search of my car found a water bottle, which I pushed into the snow to serve as an anchor at one end, and my windshield scraper, to which I tied the other end. The antenna, made of cheap speaker wire, was up in about 10 minutes. Since I was in my car, I just plugged the radio into the lighter socket. But I would normally run it with my fish-finder battery. In fact, the radio will work just find on as little as a 9-volt battery, although I’m guessing one battery would last less than an hour or so. A better compromise for small size but reasonable battery life would be 8 AA batteries or 8 D cells.

As soon as I turned on the radio, it sprang to life, and I made a total of 34 contacts over the course of two hours. You can see from my log below, the radio does get out. The log image below was made shortly after the contest and confirmations continue to trickle in, but other states worked included Texas, Louisiana, New York, and Pennsylvania, as well as Ontario, Canada. Surprisingly, I worked nothing to the west, but there are a couple of explanations. Forty meters is primarily a nighttime band, and it was still daylight to the west of me. Also, the antenna had an east-west orientation, meaning that it would get out the best to the north and south, which explains the good signal into Texas and Louisiana.

If you see your call sign here, thanks for the contact. And if you don’t see your call sign here (or if you don’t have a call sign yet), I look forward to seeing you on the air next year! Maybe by then I’ll try out QRP Labs’ QDX digital transceiver. Starting for just $69, it’s a multi-band digital transceiver. It plugs into your computer, and you can immediately start bouncing your signals off the ionosphere into other states and countries. If you get the entry-level technician license, you can use it immediately on 10 meters. While that band is very hot right now, that’s not always the case. Therefore, I would recommend also taking the test for the slightly more difficult general class license. But you’re in luck, as I’m also the author of a study guide for that test.

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SWL’ing Missile Launches and Nuclear Blasts

Sixty years ago this month, the British Radio Constructor carried the plans for this interesting project, suitable for monitoring missile launches. Or, if you were lucky and happened to be tuned in at the right time, you could hear the signature RF signals of a nuclear blast going off!

The project itself was quite simple. It consisted of a loop antenna, feeding to a one-transistor ELF detector and one stage of audio amplification.