Author Archives: clem.law@usa.net

1947 FM Converter

1947AprPMFMconvPrior to World War II, the relatively new FM broadcast band was located at 42-49 MHz. After the war, it moved to its current home at 88-108 MHz. This false start was one of the reasons why FM took years to catch on: The early adopters owned receivers which were now useless, since the stations had all moved.

One solution was building a converter, and a number of designs were available. One of the simplest is shown here, and appeared in the April 1947 issue of Popular Mechanics.

The circuit originated with Henry R. Kaiser, the chief engineer of FM station WMOT in Pittsburgh. When WMOT changed frequencies, there were about 6000 obsolete receivers in the area which could no longer hear the station.

Kaiser originally designed a circuit with a crystal oscillator, and a 1N34 diode as mixer. During experiments, the tube oscillator failed. Much to his surprise, the circuit converted the frequency of another FM station. With a bit of tweaking, he came up with this circuit which put his station on the old receiver’s dial without any power.

The article doesn’t explain how the circuit works, probably because the author didn’t know. But at least for a strong signal, the circuit did work, and could be used to put some of those obsolete sets back in service.

1947AprPMFMconvschematic



75th Anniversary of End of Civilian Radio Production

1942MayRadioRetail

As we previously reported, on this date 75 years ago, April 22, 1942, the last civilian radio receivers rolled off the assembly lines.  For the duration of the war, no more radios or phonographs would be produced, the nation’s industrial output instead being devoted to the war effort.

The photo here shows one of the last RCA radios to be produced before the deadline.  This ad, which appeared in the May 1942 issue of Radio Retailing, shows RCA Victrola No. 17,199,547, which was the last set to be produced at RCA’s Camden plant, on April 7, 1942.

With no more new sets available, the nation’s radio servicemen were acutely aware that they would bear the full responsibility of keeping the nation informed and entertained by keeping existing sets running.

 



1942 Aircraft Detector

1942AprRadiocraftCover

Seventy-five years ago this month, the April 1942 issue of Radio Craft showed the defense-minded electronics hobbyist or serviceman how to put together this aircraft detector. According to the magazine, the detector would be of particular interest to civilian defense units around the country. Cost of parts was set at $50, and the detector used readily available parts. In tests, it was able to pick up conversations at three blocks, and the sound of a bomber ten miles away.

Detail of horn-microphone assembly.

Detail of horn-microphone assembly.

The “ear” consisted of an old phonograph horn with a sensitive microphone mounted at the base. The four-tube battery operated amplifier employed three 1H5GT and one 1G4G tubes and allowed the operator to scan the skies for approaching planes with headphones.

 



1942 Midget 3 Tube TRF

1942AprPS11942AprPS2Seventy-five years ago this month, the April 1942 issue of Popular Science showed how to put together this midget 3-tube broadcast receiver. The set was said to provide loudspeaker volume for stations up to fifty miles away. Thanks to the miniature tubes employed, the set could fit into a woman’s handbag.

The set used a type 9003 pentode as RF amplifier, with a type 9002 triode serving as detector. A 70L7GT dual tube served as audio amplifier and rectifier. The filaments were wired in series, with a 200 ohm line cord dropping the voltage.



For an antenna, the article recommended about 15 feet of stranded wire lying on the floor.

1942AprPSSchematic



Wake Up America Day 1917

A hundred years ago, April 19, 1917, it was “Wake Up America Day,” an event designed to boost recruiting for the First World War.

The days main event was a parade in New York City.   In the photo here, Abraham Lincoln impersonator Benjamin Chapin is shown riding in an antique coach.  He is followed by Boy Scouts bearing illuminated signs with the points of the Scout Law, along with the words, “We are coming, Father Abraham, thousands strong.”



1942 Ground Current Communication

1942AprQST

During World War II, Amateur Radio was off the air for the duration. However, unlike the situation in the First World War, hams were allowed to keep their equipment, and there were no restrictions on listening. Hams were eager to communicate, and with radio unavailable, they were eager to explore other possibilities. Starting with the March 1942 issue of QST, each issue included an experimenters’ section, which discussed many of the possibilities. Among the possibilities were carrier-current radio over power lines, and modulated light beams.

The first ideas started to trickle in 75 years ago this month in the April 1942 issue, and some of the first experiments focused on ground current communications. Leslie C. Merrill, W1NEI reported his preliminary results with the schematic shown above. The receiver consisted of the audio section of his receiver, and the transmitter consisted of the venerable spark coil from a Model T.

From the transmitter, the signal was fed to ground rods three feet apart. At the receiving end, the ground rods were only two feet apart. Despite the close spacing, he was able to copy the signal fifty feet away.

Merrill reported that he lived out in the country, and had the possibility to space ground rods 3/8 mile apart. By extrapolating his initial results, he speculated that a range of 30 miles might be possible with a similarly equipped station at the other end.

We’ve previously covered similar ideas.  In 1940, Popular Mechanics carried plans for a similar setup with a range of about 75 feet.  And in the First World War, the Signal Corps had a field buzzer that could be configured with a similar setup.  And a 1957 “Quist Quiz” showed a similar setup using a telephone, and even noted that old timers would be familiar with such a hookup.



Escape of Gen. Giraud, 1942

Gen. Giraud during his daily walk during imprisonment, 1940 or 41. Wikipedia photo.

On this day 75 years ago, April 17, 1942, French General Henri Giraud escaped from prison in the Nazi Königstein Fortress near Dresden, one of the largest mountain fortresses in Europe.

In 1940, Giraud was commanding in the Netherlands where his men were trying to block a German attack through the Ardennes.  He was at the front with a reconnaissance patrol when he was captured by German troops.

Giraud spent the next two years planning the escape. He spent the time learning German, memorizing a map of the area, and making ropes out of smuggled-in pieces of twine, copper wire, and bedsheets.

Just before the escape, the 63-year-old General shaved his mustache, climbed the wall, and descended the steep rock on which the fortress lay. He jumped aboard a moving train, and eventually made his way to Switzerland, from which he transferred to Vichy France.

When word of the escape spread in France, the Nazis were beside themselves, and an order to assassinate Giraud was issued, along with orders to arrest his family members.

He tried to talk Marshal Pétain out of continued collaboration, to no avail. He was then secretly contacted by the Allies, and eventually took a submarine to Gibraltar, where he met with General Eisenhower. He was flown to Algiers in November, but Vichy French forces there initially refused his command and his plea to join the Allies.

Giraud’s 1942 escape was actually his second escape from the Germans. In the First World War, he was wounded and left for dead on the battlefield before being taken prisoner and placed in a prison camp in Belgium. He escaped after two months by pretending to be a roustabout with a traveling circus, eventually returning to France via the Netherlands.



Happy Easter!

Happy Easter from OneTubeRadio.com!

Was it a morning like this?



Texas City Disaster, 1947

Parking lot a quarter mile from the blast. Wikipedia photo.

Today marks the 70th anniversary of the deadliest industrial accident in U.S. history, the Texas City disaster of April 16, 1947, which started as a fire aboard the French-registered vessel SS Grandcamp docked at Texas City, Texas, with 2200 tons of ammonium nitrate. The disaster killed at least 581 people, including all but one member of the Texas City fire department.

Smoke was spotted in the cargo hold of the Grandcamp at about 8:00 AM. The captain ordered his crew to steam the hold, which probably made matters worse by converting the ammonium nitrate to nitrous oxide.

Spectators gathered, believing that they were a safe distance away. The sealed hold began to bulge, and water splashing against the hull began to boil.

The cargo detonated at 9:12 AM, with a blast leveling over a thousand buildings on land and destroyed the Monsanto chemical plan and ignited refinery and chemical tanks on the waterfront. Bails of twine from the cargo were set afire and hurled around the city. People in Galveston, 10 miles away, were forced to their knees, and the shock wave was felt as far as 250 miles away.

The ironically named SS High Flyer was docked nearby, and the blast set fire to that ship’s cargo of ammounium nitrate. Fifteen hours later, that ship exploded.

As might be expected, the blast destroyed much of the city’s communication infrastructure, and amateur radio operators quickly responded to fill the gap.  Many of these stories are detailed in the July 1947 issue of QST (pages 38-40).

B.H. Standley, W5FQQ, on the air at city hall, along with city clerk Ernest Smith, Nurse Mrs. E.L. Brockman.

B.H. Standley, W5FQQ, on the air at city hall, along with city clerk Ernest Smith, Nurse Mrs. E.L. Brockman.

By noon, the first amateur portable and mobile stations had moved into the city and were on the air, working in conjuction with Army, Navy, Coast Guard, U.S. Engineers, FBI, and local and state police. Links were quickly set up between City Hall and stations in Houston and San Antonio. Most traffic was handled on 75 meter phone and 80 and 40 meter CW. W5KMZ reportedly handled over 200 messages, mostly involving needed medical supplies. As the hours went on, additional traffic was handled by W5FQQ at the mayor’s office, with over 300 messages passing on behalf of city officials, the Army, Red Cross, and Salvation Army.

An impromptu three-way net was established on 3989 kHz between Texas City, Galveston, and Houston.

Two hams, W5FQQ and W5EEX, had been advised to evacuate but remained at their stations. They narrowly escaped death when the High Flyer lived up to its name with its explosion. W5FQQ was on the air at the time of the blast, and the blast was heard by W5IGS in Houston. 21 seconds later, the Houston station experienced his windows shaking.

W1AW declared the emergency to be over 11 days later, on April 17.

As might be expected, considerable litigation followed, much of it under the Federal Tort Claims Act for alleged negligence of the U.S. Government. The case ultimately made its way to the U.S. Supreme Court, Dahelite v. United States, 346 U.S. 15 (1953), in which the court held that the Government was not liable, since all of the claimed government negligence amounted to discretionary acts.



1977 Fish Attractor

1977101projectsWe previously showed you the modern electrical method to catch worms.  (In fact, if you catch too many for your fishing needs, we even showed you how to make big money selling worms.)  But now that you have all of those worms, you’ll want to take them fishing, and this electronic project from 40 years ago practically guarantees that the big ones will start biting.

The circuit puts out a repeated click-click sound which is reportedly a dinner bell for fish.  With this circuit in a suitable waterproof container, the fish will be biting in not time.

The circuit appeared in the 1977 issue of 101 Electronic Projects, a special edition put out by the publishers of Elementary Electronics.