Category Archives: Radio history

1941: How Radio Will Defend America

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On this date seventy five years ago today, October 18, 1941, less than two months before Pearl Harbor, Radio Guide magazine told all the ways that radio would defend America.  The author, an army officer who had previously served as an editor of the magazine, started by saying that the bombers would come first, make no mistake about it. They would do it, unless radio prevented them, as one of the nation’s first line defenses. He noted that the shores were ringed with listening stations on our territory, on distant islands and ships at sea, and aboard blimps above the ocean. One of those stations would see them coming, and radio would carry the message to commanders whose duty it was to defend our shores.

If enemies did get through, then “radio must do for America what it failed to do for France; it must tell Americans where to go and by what routes. When areas need to be evacuated, radio must instruct automobilists and truck-drivers to use certain roads and highways. The Army has first claim on the others. Indeed, it may be a part of one’s preparedness to keep his radio continuously tuned in. No other means can tell the public so quickly of threatened danger.”

Another aspect of national preparedness was monitoring foreign shortwave broadcasts. “Would you think, for example, that by listening to what Germans are telling Americans, both in North and South America, you could learn what Germany may do next? Well, you can. Even now German short-wave stations are talking to us at all hours. Each twenty-four hours they are sending us thirty thousand words of trickery and deceit. By following it for month after month we have learned that it assumes a pattern that is visible to experts. Our own Federal Communications Commission hires such experts and many others besides to listen to all foreign language broadcasts. Stations in Oregon, Texas, Maryland and Puerto Rico hear all broadcasts directed to this country and to South America. They make recordings of these broadcasts, turn them over to translators, then to analysts, then to psychologists. Result: The American government was warned ahead of time that Japan was going to occupy Indo-China. Germany’s attack on Russia was predicted within a few days.”

Air Corps radio operators.

Air Corps radio operators.  “A few months ago many of them were ‘hams’ you heard on short waves. Today they’re learning everything from signal codes to radio night-fighting technique.”

The article also noted how broadcasting had served the public by providing information and quieting rumors.  It concluded by noting that in peace, Americans had used radio better than any other nation.  “We have more stations, more receivers, more artists, more technicians, more listeners.  In war, if it comes, we shall also use radio best–there can be no doubt of that–and employ its multitude of services in order that a complete and glorious victory may quickly be ours.”



NPOTA: Lewis & Clark National Historic Trail

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Preparing to send RF ‘cross the wide Missouri.

During the 2016  ARRL National Parks On The Air (NPOTA) event,  Amateur Radio operators are celebrating the 100th anniversary of the National Park Service (NPS) by setting up their equipment in NPS units  to make contact with other Amateurs around the world.  Since the beginning of the year, the event has been extremely popular, with over 13,000 activations from 450 different different units of the NPS and over 700,000 individual two-way contacts.  As I’ve reported in other posts, I’ve made contact with 281 different parks and operated multiple times from six parks in Minnesota and Wisconsin.

One of the event’s successes has been encouraging visits to the parks.  Until recently, my activations have been confined to the NPS units in Minnesota and Wisconsin.  Last week, I had to be in Sioux City, Iowa, for one of my continuing legal education programs.  The city lies along the path taken by Lewis and Clark as the traveled from St. Louis to the Pacific Ocean, and is therefore part of an NPS unit, the Lewis and Clark National Historic Trail.  Because the trail’s sheer length, and because it passes through so many other notable sites, it is the NPOTA’s most popular activation site, with over 13,000 individual contacts made.  Since my son had recently been studying Lewis and Clark in school, I decided to bring him along.

Sioux City marks the point where the only death during the 1804-06 Corps of Discovery’s expedition took place.  Sgt. Charles Floyd is buried under a prominent obelisk on a bluff overlooking the river.  The Sioux City riverfront contains two museums devoted to Lewis and Clark’s journey.  The first is in a drydocked former riverboat, the M/V Sergeant Floyd.  The ship was an Army Corps of Engineers Inspection Vessel.  Interestingly, the ship contains a ham station, although it’s supposed to be a recreation of the ship’s radio room.  As you can see from the photo below, the radio room is equipped with an E.F. Johnson Viking Valiant and a Hallicrafters S-40.  Even though these amateur rigs appear to be out of place, it was interesting to see this inadvertent ham station set up.

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dsc01371The museum also contains the forensic reconstruction of Sgt. Floyd shown here, created from a plaster cast of his skull.

The second museum on the riverfront is the Sioux City Lewis & Clark Interpretive Center, which includes animatronic versions of Lewis, Clark, President Jefferson. and “Seaman,” the expedition’s Newfoundland dog.

Conditions were relatively poor the day I visited the site, and my initial attempt with a mobile antenna was unsuccessful.  Since the day was nice, I returned and set up a dipole at a picnic shelter overlooking the river and made ten contacts on 20 meter CW.

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Wartime Lamp Radio

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Despite wartime parts shortages, the young man shown here was able to furnish his room with a radio, courtesy of plans found in the October 1944 issue of Popular Mechanics.

The lamp is not merely ornamental; it is part of the circuit. The 40-watt bulb serves to drop the line voltage to light the tube filaments. Two tubes are used, either type 37 or 76. The article noted that these tubes could be found in an old set, or in the radio student’s junk box. One served as a rectifier, with the other one serving as regenerative detector. The cabinet is a wooden file box. The lamp socket comes from the dime store and is mounted on a curtain rod secured to a wooden block on the cabinet with glue. The switch on the lamp socket turned on both the lamp and radio.

The coil was wound on a cardboard tube, and wire from an old transformer or filter choke could be used.

The set was billed as a “Desk Lamp DX’er for Boy’s Room.” For best selectivity on local stations, the article recommended an indoor antenna of 15 feet. For pulling in DX, it recommended a long and high outdoor antenna.

The article notes that no external ground is used, but doesn’t explain why not. Since the set is connected directly to the AC wiring, adding an external ground would run a 50/50 chance of blowing a house fuse (or in a modern home, popping a GFI). And anyone planning to make a modern recreation should be aware that the set isn’t exactly safe. One side of the headphones is connected directly to the AC line, and the antenna connection has only one capacitor between it and a hot wire. So the modern parent, before giving one of these interesting sets to Junior to put in his room, would probably be well advised to include an isolation transformer.

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1956 Boys’ Life SWL’ing

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Notwithstanding the microphone and bug shown in the photo, the young ham shown here in the October 1956 issue of Boys’ Life is honing his SWL skills in preparation for the magazine’s forthcoming shortwave listening contest which would be announced the following month.

The accompanying article gives scouts pointers on the shortwave listening hobby, and reminds readers that there were a lot of interesting signals to be pulled in by even inexpensive receivers.  It pointed out that aspiring SWL’s should first take a look at the family’s radio in the living room, since there was a good chance that it pulled in the shortwave bands in addition to standard broadcasts.

The article appears to be a reprint of the same article that appeared in the October 1952 issue.  The author was Roger Legge, who penned the “English Broadcasts to North America” feature in Popular Electronics for many years.  The byline of the 1952 article also identified him as the Frequency Assignment Officer of the Voice of America.

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1941 Two-Tube Superhet

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Seventy-five years ago this month, the October 1941 issue of Popular Science showed how to put together this two-tube superheterodyne broadcast set. With a 20 foot antenna lying in the floor, the set would provide loudspeaker volume.

The article noted that even a few years earlier, a superhet would consist of at least seven tubes. But with advances in tube technology, this two-tube set was now possible. A 1A7GT pentagrid tube served as first detector and local oscillator. This was fed to the triode section of a 1D8GT which served as detector. The other half of the 1D8GT served as audio amplifier to drive the speaker.

This was a battery set, with a 1.5 volt dry cell running the filaments. The B+ voltage came from a 90 volt battery, with a 7.5 volt C battery also used.

Since batteries were in relatively short supply during the war, it’s likely that any readers who built this set probably left it on the shelf for most of the next four years.

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1956 British Two Tube Receiver

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This simple two-tube broadcast receiver appeared sixty years ago this month in the October 1956 issue of the British Radio Constructor magazine.

One tube serves as the regenerative detector, with the other tube serving as AF amplifier to drive the speaker.  The set uses what is called a “metal rectifier,” although a modern semiconductor diode would probably be much more reliable.

The set runs directly off the AC mains, and the article notes a number of safety precautions, and the article assures that “if the precautions mentioned are taken, and the receiver fitted in a wooden cabinet, it will be quite safe.”  In particular, in addition to being completely surrounded the an insulating cabinet, the article notes that all metal components must be insulated.  The knob on the tuning capacitor must be covered with a non-conductive knob (with the hole for the setscrew filled in with insulating material), the switch must not come in contact with the chassis. and the bolts holding the chassis to the panel must be covered.  The plans give instructions for wiring the set for either 110 or 250 volts.

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Knight Kit Star Roamer

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Fifty years ago this month, the October 1966 issue of Popular Electronics carried this ad for the venerable Knight Kit Star Roamer receiver.  It used four tubes, a selenium rectifier, and two diodes to cover 200-400 kHz longwave and the broadcast band through 30 MHz.  It was an ideal first receiver for the shortwave listener.  Despite the low price, in contrast to similar sets of the era, it did contain a power transformer to keep the chassis isolated from the AC line.

In another post, I have a link to a review of this set.

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Science Fair Idea: Homemade Cardboard Box Speaker

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The young scientist or engineer looking for a relatively simple but interesting project for the science fair could construct the homemade permanent-magnet speaker shown here.  It appeared fifty years ago this month in the October-November 1966 issue of Radio-TV Experimenter.

The speaker is constructed inside a cardboard box, which also serves as the sounding board (which the article incorrectly calls a “cone,” which it would be in a normal speaker).

The only other components, aside from a few pieces of cardboard and glue, consist of a permanent magnet and wire. Just as in a commercially manufactured speaker, a coil of is mounted on a form surrounding the magnet. When an audio signal is applied to the coil, it and the top of the box are made to vibrate.

The 1965 plans call for a magnet from a burnt out speaker, and this would still be a possibility.  These days, a more prolific source of powerful magnets would be from the drives of defunct computers, as shown in this video:

Suitable magnets are also available from Amazon or many other sources.  These plans call for a coil of 75 turns of 30-gauge enamel wire, although the exact wire size is not critical. The original plans call for using the speaker with a radio or television. The simplest way to make the connection to a modern radio or MP3 player would be through the headphone jack. Another option would be to use an inexpensive audio amplifier such as the one shown below:

The use of an audio amplifier would also allow the use of a homemade microphone, such as one of those shown in an earlier post.  And for another somewhat more complex homemade speaker (or microphone), see this post.

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1966 GE Rechargeable Portable

1966sepelecworldFifty years ago, the September 1966 issue of Electronics World showed this General Electric transistor portable with a rechargeable battery.  It came with a detachable base containing a clock, which also served as the charger.  The battery was said to power the set for up to twelve hours after an overnight charge.

As seen from the headline, one notable feature was the fact that the set contained integrated circuits, and GE engineers predicted that all of their products would contain IC’s by 1970.

Citing the set’s reliability, GE offered a three year warranty, including the battery.

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Radio On The Farm, 1926

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Shown here ninety years ago in the September 1926 issue of Radio Age magazine is Charles Ostrand, described by the magazine as a farm boy from Shawnee County, Kansas. He built the three tube set shown here in order to listen to helpful agricultural programs. The magazine reported that he had built several other sets for his neighbors.

This was not an unusual phenomenon. According to the magazine, there were already a million radios on the nation’s farms, and the U.S. Department of Agriculture predicted that the number would soon double. The radio, according to the magazine, was not just a device for entertainment. It delivered weather and market reports, as well as vital scientific information of use to farmers.

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