Author Archives: clem.law@usa.net

Science Fair Idea: Eddy Currents

Eddy currents in solid core (left) and laminated core (right). Wikipedia image. This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.

This simple experiment from eighty years ago shows how to experimentally verify the existence of eddy currents in the core of an electromagnet or transformer.

A coil of wire through which house current is passing is wound over two cores. One half is a solid piece of iron, and the other half consists of pieces of wire bundled together. The magnetic field in the coil, which changes direction 60 times per second, sets up eddy currents in the solid core, and the result is that it becomes noticeably warm. In the core consisting of wire, the currents are broken up, and the effect is not noticed.

Of course, it goes without saying that the aspiring scientist should be careful using household current in an experiment. But as long as all of the connections are properly made and insulated wire is used, the experiment is perfectly safe, and would make a good science fair experiment.

The image is from the December 1936 issue of Popular Science.

In transformers, eddy currents are undesirable, since they cause unwanted heat and inefficiency. However, they have some practical applications, such as levitation and braking.

Peace Light and NPOTA: Herbert Hoover National Historic Site

I was recently in Iowa to present some Continuing Legal Education programs in Cedar Rapids and Des Moines. Whenever possible, I like to combine trips, and I used this opportunity to take part in two other events.

Cedar Rapids is close to the birthplace of Herbert Hoover in West Branch, Iowa. It is the location of the Herbert Hoover National Historic Site, as well as the Hoover Presidential Library and Museum. I’ve been looking forward to putting this National Park Service (NPS) unit on the air during the NPS Centenial year as part of the ARRL National Parks On The Air (NPOTA) event. During this event, Amateur Radio operators are 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. There have been over 900,000 individual two-way contacts made from the parks, and it appears almost certain that this number will top a million before the end of the year. As I’ve reported in other posts, I’ve made contact with over 300 different parks and operated multiple times from parks in Minnesota, Wisconsin, and Iowa.

I was especially eager to operate from President Hoover’s birthplace, since he played such an important role in the history of radio. Indeed, his son was an avid amateur radio operator, and served in the 1960’s as president of the American Radio Relay League, the national organization sponsoring the event.

I didn’t have time for a long operation, but I was able to spend about an hour operating from the parking lot of the historic site’s visitor center, as shown in the photo above. President Hoover’s birthplace home is barely visible in the photo (just to the left of the larger building in front of the car. Despite the short time available, I managed to make contact with about 30 stations, all CW (Morse Code), ranging from Alaska to Florida. After operating, at dusk, I paid my respects at the gravesite of President and Mrs. Hoover, shown here.

The next day, I used my drive home to the Twin Cities to transport the Peace Light of Bethlehem from Des Moines to the Twin Cities.

For at least the past several hundred years, and possibly more than a thousand, a lamp has continuously burned at the grotto of the Church of the Nativity in Bethlehem, the traditionally accepted location of Christ’s birth. Since 1989, the Boy Scouts and Girl Guides of Austria have annually sent a child to Bethlehem, who lights a lamp from the light and returns it to Austria. From there, it is passed on around Europe during the Advent season. Since 2000, the Peace Light has been delivered to North America where volunteers, most of whom are connected with Scouting, deliver it around the country.

This year, there was a gap in the distribution, and it wasn’t making it to the northern tier of states. I coordinated with members of the Peace Light North America Facebook group, and made arrangements to meet with an Iowa Scouter in the parking lot of a Des Moines coffee shop. From his kerosene lantern, we lit my lanterns, shown here, and I took the burning lanterns home.

From there, others have come to light their candles and lanterns, and the same ancient flame is burning in lamps in Minnesota and Wisconsin. Another volunteer from North Dakota is on the way here, and within a few days, the Peace Light will be burning in North Dakota, Manitoba, Montana, Washington, and probably other places along the way.

Many are curious as to how the Peace Light crosses the Atlantic. It is transported by Austrian Airlines in the passenger cabin of an aircraft. The ailine transports the flame from Israel to Austria, and then to New York and Toronto. The flame is held within a blastproof miner’s lamp, which allows the open flame to be transported safely by air. At Kennedy Airport, it’s walked through customs by an airline employee to the airport chapel, where a ceremony is held attended by those who fan out around the country to transport it. Among those were one or more volunteers who transported it to Chicago. From there, it went to Davenport, Iowa, where it was picked up by the person who gave it to me.

December 4, 1941: Three Days to War

Seventy-five years ago today, America’s entry into the war was three days away, but the signs were clear that it was coming soon. The Chicago Tribune, December 4, 1941, carried this headline of FDR’s plans for war.

The front-page cartoon makes clear that the paper was decidedly in favor of neutrality and opposed to intervention. It shows a Midwestern bastion of peace, looking with alarm at what it viewed as pro-war propaganda from Washington.

The war plans, consisting of documents from the War Department and letters from the administration, had been obtained by the paper and the contents were disclosed. It showed the likely enemies as Germany, Italy, Spain, and Japan, and anticipated theaters of war in both Europe and the Pacific. It also stressed the importance of maintaining solid relations with the republics of the Americas, since trade with both Asia and Europe would probably be cut off for the duration. It called for ten million American men to take up arms, with half of those to serve in an Expeditionary Force to Europe, with a ground offensive slated to begin in 1943.

Another cartoon in the same issue of the paper restated what the paper viewed as Midwestern pro-peace values, insisting that we raised our cattle, and not our sons, for slaughter.

WRUL Boston, 1941

Shown here as it appeared at the time of America’s entry into the War is the control room of Boston shortwave station WRUL. The image appeared in the December 15, 1941, issue of Life Magazine.

The magazine was obviously put together immediately after the attack of December 7, since most of the articles refer to an America that was preparing for war, but still at peace. Only a middle section of the magazine includes images of the attack.

This image is from an article profiling the shortwave station which, according to the magazine, the Nazis hated and feared.

It was billed as the nation’s most powerful shortwave transmitter, and was “waging a mighty war of propaganda against Adolf Hitler and his allies.” The station’s transmitters were 50,000 and 20,000 watts, with plans to increase. Programs went out day and night in 24 languages.

The station had come on the air in 1927 under experimental license W1XAL. With the outbreak of war in Europe, unbeknownst to the staff, the station came largely under the control of British Intelligence. With America’s involvement in the war, the station was leased to the U.S. Government. In 1962, under new ownership, the call letters were changed to WNYW for “Radio New York Worldwide,” with studios in New York and the transmitter reamining in Scituate, Mass. In 1973, the station was acquired by religious broadcaster Family Stations, Inc., and operated as WYFR until that station moved its transmitters to Okeechobee, Florida, in 1979.

WWV Moves to Colorado: 1966

Today marks the 50th anniversary of WWV’s move to its current location in Fort Collins, Colorado. At 0000 hours GMT on December 1, 1966 (5:00 Mountain Standard Time on November 30), the station began its transmissions from the new location on the familiar internationally allocated standard carrier frequencies of 2.5, 5, 10, 15, 20, and 25 megacycles.

The move was announced in the November 1966 issue of Electronics Illustrated, which contained the photograph shown above. At the center of the photo is the station’s 10 MHz dipole antenna. The 3-1/8 inch diameter transmission line can be seen snaking off to the right. In the background to the left is the WWVB transmitter building (WWVB and WWVL had previously been located at Ft. Collins). The antennas in the background are, at the left, a backup 88 foot monopole, and at the right, the 400 foot WWVL tower.

NIST photo.

To celebrate the move, the station issued a special first-day QSL card for reception reports on the first day. To ensure that SWL’s had really picked up the station, the voice identifcation used a special message on the first day, which had to be copied exactly to receive the special QSL, which is shown here.

According to the accompanying note on the card, WWV had apparently planned to award a photograph of the new station to the first three reception reports. However, it proved impossible to determine which were the first three, and three were selected from the batch. One of those went to long time ARRL staffer Lewis “Mac” McCoy, W1ICP.

The station had previously been located at Greenbelt, Maryland. The move was designed to give better coverage and to move the station closer to the National Bureau of Standards’ frequency standard lab in Boulder, Colorado.

1936 Popular Science Portable Transmitter

Eighty years ago, the November 1936 issue of Popular Science carried the plans for this portable 20 watt AM transmitter for 160-20 meters.

The compact transmitter was designed for operation on a 6-volt storage battery, with a motor-generator supplying the B+ voltage. Also included were plans for an AC power supply.

A type 42 tube was used for the crystal oscillator, with a 6A1 final amplifier. Modulation was handled by two 6A6 tubes.

1943 Emergency Blackout Receiver

The November 1943 issue of Popular Mechanics carried the plans for this wartime emergency receiver. Built in a cigar box, the set was an updated version of the “Hurricane Receiver” previously published by the magazine and featured here earlier.

The article noted that the set could be used under blackout conditions in areas where a power line would be unavailable. Both the filaments and B+ were provided by six volts, which could come either from dry cells, or obtained from the nearest automobile. For portable use in shelter conditions, the article suggested a wood carrying case such as shown here for transporting the battery.

The set was said to be of considerably more volume and greater range than the original model. It employed two 6G6-G tubes, and the article noted that these tubes were commonly found in the junk boxes of radio students, experimenters, and servicemen. The set employed one tube as the regenerative detector, with the second one serving as audio amplifier.

The coil was wound on a cardboard tube, and the wire could be salvaged from a burned out choke or audio transformer. A ground connection was recommended for maximum results, and a 20 foot indoor antenna could be used for local stations, although a longer outdoor antenna would pull in stronger signals.

With this set and a 6 volt battery, the owner would be able to listen to local stations for emergency safety and blackout instructions.

World’s Largest One Tube Radio, 1923

At OneTubeRadio.com, we appreciate one tube radios of all varieties, but in general, the bigger the better.

In 1923, the one shown here was billed as the world’s largest one tube set. The set is being operated by Miss Agnes Leonard, at the Radio Show being held at the Grand Central Palace, New York City. The photo appeared in the November 1923 issue of Radio Topics.

1916 Victrola

A hundred years ago today, the November 26, 1916, issue of the Chicago Tribune carried this Victrola ad.

For $79.50 (or a dollar a week until paid), you could take home the Victrola, along with 12 selections of music (6 double-sided records). It was offered on a 30 day free trial, and the seller was confident that you would want to keep it as a permanent member of the family.

It was sold by the P.A. Starck Piano Company of 210-212 S. Wabash Avenue, Chicago.

1916 Wireless School

The young men shown here a century ago are training to become wireless operators at the Montreal wireless school operated by the Marconi Company. The school had opened on June 1, 1916, and was under the direction of instructor in charge Mr. Douglas R.P. Coats, who is shown standing behind the back row of students.

In order to make the training resemble as closely as possible actual working conditions, specially designed apparatus and automatic transmitting devices were used. The school also had the latest 17 kW apparatus available, and other installations were to be installed.

The photo appeared in the November 1916 issue of Wireless World.