1973 ZN414 Receiver

Screenshot 2023-01-12 12.19.59 PMFifty years ago, this British woman probably had the smallest radio receiver on her block, and she constructed it herself, thanks to the plans contained in the January 1973 issue of Popular Wireless. The set owed it’s diminutive size to then-revolutionary ZN414 integrated circuit, manufactured by Ferranti, which contained all of the circuitry for a tuned radio frequency (TRF) AM receiver onto a single chip. The chip’s specs covered long wave up to about 5 MHz, but in a prototype made by the magazine, the chip was able to cover the 49 meter shortwave band. The version shown in the magazine covered the medium wave band, but could be easily moved to different frequency ranges. For strong stations, the set sometimes tuned broadly, but when two stations were close together, it would separate them, even if one was strong.

The small set had good sensitivity, and tuned in Radio Luxembourg loud and clear. Audio was through a crystal earphone. The case for the radio was a snuff container, which the author reported could be purchased for 9 pence (including the snuff). The author added that “if you haven’t tried snuff, this is your chance,” and that he was partial to the occasional pinch.

The ZN414, like most things, is available on eBay. But it’s replacement, the TA7642, is readily available for those seeking to duplicate this project.

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Radio Caravan Promoting 1925 Portland Atlantic-Pacific Highways and Electrical Exposition

Screenshot 2023-01-11 2.05.01 PMShown here in Popular Mechanics a hundred years ago this month, January 1923, is an automobile caravan promoting the 1925 Atlantic-Pacific Highways and Electrical Exposition, to be held in Portland, Oregon. The caravan toured Eastern Oregon to promote interest in the exposition. It included Army radio operators who demonstrated the apparatus, and for many rural citizens, it was the first time that they had seen or heard a radio.

Perhaps some of them went on to acquire the set shown below, which was also featured in the same issue of the magazine. The portable set, intended for use by non-technical radio fans, The entire set, including batteries, measured only 7 by 9 by 11 inches. According to the magazine, the set was tested near Galveston, Texas, where it solidly pulled in concerts from Georgia, Tennessee, Kansas, and Missouri, despite what were described as troublesome radio conditions endemic to Texas. Even more distant stations were also received at times.

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US Navy Blimps of WW2

Screenshot 2023-01-11 12.53.05 PMLike most veterans of World War II, my dad never spoke very much about his service, and it never occurred to me to ask about it. I know that he was a Machinist Mate in the U.S. Navy, and I know that he was assigned to a Blimp HedRon near the Caribean.  He was one of about 12,499 Navy personnel assigned to blimps.  He enlisted in 1943, so this article predates him, but the January 18, 1943 issue of Life magazine shows how blimps were used to patrol waters off the coast of the United States to scout for enemy submarine activity.



Unwinding Twisted Pair: 1948

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Seventy-five years ago this month, the January 1948 issue of the British Practical Wireless showed this self-explanatory tip for unwinding twisted pair.

The idea was sent into the magazine by one R.L.G. of Chelmsford, who pointed out that it was often necessary to unwind a long length of “lighting flex,” which was apparently in common use in Britain for home lighting circuits. But he points out that any amateur who has attempted this learns that it becomes tedious after a few feet. With the device shown here, it was an easy matter. You just pull the wire taut, and start twisting (usually clockwise). In just a few minutes, the wires will separate. It is necessary to move back slowly, as the wires get longer when unraveled.



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WWV, 1953

1953JanBLSeventy years ago this month, the January 1953 issue of Boys’ Life carried this illustration showing some of the uses to which the signal of WWV could be put.

The railroad and the factory worker were on time thanks to the time broadcasts. The time was announced every five minutes, in both Morse code and voice. The Morse was in GMT, and the voice was Eastern Standard Time. The musician took advantage of the standard 440 Hz tones, which were the A above Middle C.

The code key represents an idea shown by the magazine. For an easy code practice set, you could put the key in line with a pair of headphones and tune into WWV. Then, you could key the tone on and off.

In addition, the station sent radio propagation disturbance warnings, with the Morse W, U, or N. W meant warning, U meant unstable, and N meant normal.



1963 Stealth Antennas

1963JanEIIt’s become a more common issue these days, but even 60 years ago, some hams and SWL’s were faced with the issue of needing to put up an antenna where they weren’t allowed. As highlighted by this article in the January 1963 issue of Electronics Illustrated, one solution, then and now, is to use an invisible antenna. The easiest way to do that, as apparently done by the owner of the antenna shown above, is to use a very thin gauge wire. The article suggested 18 gauge or smaller (larger numbers being smaller). The best choice is often enamel wire, and it is sometimes possible to select a color that matches the background, for added stealth.

I’ve discovered that one source of very cheap almost invisible wire is cheap speaker wire.  Remember, when you see the price per foot, you’re actually only paying half that much, since you can unzip the wire before using it.  And it often comes with clear insulation, meaning that it’s almost invisible from even a short distance away.

The magazine suggested a type of insulator to use, but modern hams have discovered that the insulator is often unnecessary. Instead, just tie the end of the wire to a piece of monofilament fishing line, which is even less visible.

The article also suggested the possibility of becoming patriotic and installing a flagpole on your house. Especially for higher frequencies, they can form the basis for an excellent antenna system.



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Polar Bear Mushing: 1923

Screenshot 2023-01-11 1.18.43 PMA hundred years ago this month, the cover of Popular Mechanics for January 1923 showed a self-explanatory transportation idea that, for some reason, never caught on. For the really big loads that sled dogs couldn’t handle, simply replace the dogs with polar bears! They’re fast and they’re strong, and they could haul sleds of unimaginable size.

“While the Eskimo is, by necessity, too busy with hunting and fishing to attempt training the bear in a serious way,” the manager of a fur company saw real potential in the idea. Of course, “in selecting the team, care would have to be exercised in eliminating animals showing  predisposition to temper.”

So even though the Inuit who had lived there since time immemorial didn’t seize the idea–simply because they were too busy–the fur company can send a man in to tackle the job.

The idea never caught on, and we’re guessing because the man sent in to tackle the job wound up as a tasty snack for one of the bears.



1943 Food Rationing Expands

Screenshot 2022-12-20 1.28.56 PMEighty years ago today, the January 11, 1943, issue of Life magazine showed these shoppers preparing to pay for their groceries with not just cash, but with ration coupons. And this would become a more common scene as more foods, such as those shown below, were to be rationed.

The magazine noted that canned goods had been an important part of warfare since the days of Napoleon, and this war was no different. Starting later in the month, a new ration book was to be issued, and those coupons would be required for the purchase of canned or bottled soups and juices, as well as most canned, dried, or frozen, fruits or vegetables.

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Electronic Measurements Quiz

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Today’s quiz is from 60 years ago, the January 1963 issue of Popular Electronics. But the vast majority of the information is still good. The answers appear tomorrow.  How well do you know your VOM?