Category Archives: Radio history

1919 Homemade Radio Parts

1919OctRadioAmateurNewsGridLeakYesterday, we presented a homemade headphone from a hundred years ago, from the October 1919 issue of Radio Amateur News. That issue also contained a number of other homemade parts, such as the variable grid leak resistor shown above, submitted by the aptly named Arno Kluge. The part is made on bakelite or rubber, and the resistance is formed by a line of India ink traced with a compass.

The magazine also contained two capacitors, one fixed and one variable.  The fixed condenser is made using sheets of mica as the insulator.  For those wishing to make a reproduction today, the best source of mica would probably be the waveguide cover from an old microwave.

1919OctRadioAmateurNewsFixedCondenser

The variable condenser is made from two tubes.  In this case, the author used parts from an old bicycle pump.  The inner tube is shellacked, then covered with wax paper, and then shellacked again.

1919OctRadioAmateurNewsVariableCondenser



1949 Portables

1949OctPM2

1949OctPM1Seventy years ago this month, the October 1949 issue of Popular Mechanics showed off some of the new pocket portable receivers that were hitting the market. The illustrations at left show the young man fishing while listening to the “Privat-Ear” portable, which weighed in at under six ounces. The young woman is listening to the 5-1/4 ounce “Micro Pocket Radio.” Both sets took advantage of micro tubes developed during the war, and were said to retail for under $20.

Those with a smaller budge but some skill with a soldering iron could put together the slightly larger two tube set described in the same issue. It had a built-in loop antenna and used two 3S4 tubes. One tube served as regenerative detector, with the second serving as audio amplifier.1949OctPM3

The set was tested initially in Denver, where it easily pulled in all of the local stations with its built-in loop antenna. Out of town stations hit the dial at night, and with an outdoor antenna at night, stations from hundreds of miles away filled the dial.

1949OctPMSchematic



Andreas Olaf Bertnes, LA6R

Andreas Bertnes

Andreas Bertnes. From the book Vestfold i Krig by Egil Christophersen, courtesy of http://www.slektsdata.no.

Today marks the 100th birthday of Andreas Olaf Bertnes, LA6R, of Sandefjord, Norway. We previously reported the 75th anniversary of his death in 1941. He was arrested in Norway by the occupying Germans for illegally using a radio transmitter.

The QST item we originally reported noted that he was 25 years old at the time of his death and a medical student. Based upon that information, we assumed that he was born in about 1916. It appears, however, that he was younger than reported at the time of his execution. According to the Norwegian government’s publication “Våre falne 1939-1945” (Our Fallen 1939-1945), he was born a hundred years ago today, 21 October 1919. He was the son of Dr. Olaf Bernes, born 1873, and Dorothea Saxlund, born 1885.

Andreas gave his life for his country on 4 December 1941.  He was one of four amateur radio operators executed during the war for their resistance activities.  He had been active on the air before the war.  He was listed in the “calls heard” listings by an English SWL on 20 meters in November 1937 and and April 1938.

Reference



1949 Admiral 30F15

1949OctRadioRetailSeventy years ago this month, the October 1949 issue of Radio & Television Retailing carried this ad for a top of the line Admiral console, the model 30F15.  The ad noted that Admiral had a 50% market share when it came to television combinations.  This one combined an AM-FM receiver, record player, and 12-1/2 inch TV.

You can see a specimen of the set at this link, although at some point someone decided that it needed a coat of blue paint.



Wiring the Iowa State Capitol For Sound: 1939

1939OctRadioNews2For the first 93 years of statehood, the Iowa Legislature managed to carry on the people’s business without resort to electronic sound amplification. Back then, politicians presumably understood that to be successful, they needed to learn how to project their voice. But in 1939, they decided to solicit bids for an audio amplifier for the House chambers. The low bidder was Lloyd Moore of Moore’s Radio Shop, Chariton, Iowa, and he recounted his experiences with the project in the October 1939 issue of Radio News.

The first step in successfully completing the project was the preparation of a viable bid. To do this, Moore met with members of the legislative committee tasked with overseeing the project. The committee was made of of non-technical men, none of whom had any experience with sound work. A few had used a studio mike, but they were unfamiliar with the problems of having the speakers and microphone in the same room. After Moore’s patient explanation, they readily understood the feedback problem. It was explained that they would need to talk within about eight inches of the mike and use a good voice.

The sealed bid was submitted, with an adequate cushion to allow for the best equipment and a reasonable amount for the labor involved. Moore’s bid was chosen, and he set to work.

Act appropriating payment. Google books.

Act appropriating payment. Google books.

1939OctRadioNewsThe amplifier was over engineered. The power transformer was three times as large as necessary. Four stages of amplification were used. Gain was not excessive, so as to avoid any problems with microphonics. Five inputs were used, each switchable from the main console. One mike was mounted at the Speaker’s desk and one at the clerk’s. Three additional microphones were located in front of the floor, with cords long enough to extend to any speaker’s desk. Future plans called for additional microphones throughout the chamber, with a switch box used in place of the three existing mikes.

The amplifier was placed near the clerk’s desk, giving the Clerk the ability to turn microphones on and off and set the levels. They were particularly lucky that one of the clerk’s staff was “a girl, who had been an operator in a broadcasting station,” and her skill proved invaluable.

The author was honored to address the body in the use of the new system, particularly with regard to what to do in the case of feedback, and noted that this was probably the only time he would address such a distinguished body.

The legislator shown above at the microphone is Leo Hoegh, who was elected in 1936. He resigned in 1942 when called up for duty in the National Guard. He rose to the rank of Lieutenant Colonel and served in Europe. After the war, he returned to Iowa where he served as Attorney General from 1953-55 and Governor from 1955-57.

In 1957, President Eisenhower named him the head of U.S. Civil Defense and a member of the National Security Council. He was in the backyard bomb-shelter business for a time, before returning to the practice of law. He retired in 1985 and died in 2000.



Polish One Transistor Receiver, 1979

1979PolishCrystalSet1This unusual design for a one-transistor receiver came from Poland 40 years ago. Perhaps it was used to pull in reports from Radio Free Europe in anticipation of the rise of Solidarity.

It appears in the October 1979 issue of the Polish magazine Horyzonty Techniki dla Dzieci (Horizons of technology for children), which was published in the Soviet Union with the Russian title Горизонты техники для детей.  No schematic is given, but the general idea is clear from the pictorial diagram shown above.  (The mice are presumably optional.)  The small red component is a solid-state diode, the output of which is amplified by the transistor.  The blue component underneath appears to be the battery.  One side of the battery goes to a terminal of the transistor (probably the emitter), and the other battery terminal connects to the headphone, which is also connected to another terminal of the battery (probably the collector).  The polarity of the battery would depend on whether it’s an NPN or a PNP transistor.

The most unusual feature of this set is the tuning.  Two honeycomb coils are wound on flat forms.  They are then connected similarly to a variometer.  More detail can be seen in the illustration below.  The coil forms appear to be cardboard and popsicle sticks.  The set is tuned by adjusting the mutual inductance by varying the angle.

1979PolishCrystalSet2

One interesting feature of this magazine was a listing of addresses of children in Poland who desired Soviet penpals.  A copy of that page is shown below.  The names are shown in Cyrillic, followed by the full name and address in the Roman alphabet.  This is followed by a few lines in Russian with the child’s age and a short description.

1979PolishCrystalSet3



Hitchhiking with a Portable Radio, 1939

Screen Shot 2019-10-10 at 11.39.09 AMEighty years ago today, the October 1939 issue of Life magazine detailed the adventures of 21 year old hitchhiker Will Parker of San Francisco, who thumbed his way to New York thanks to the 29 motorists who stopped to give him a lift. He was accompanied by his friend and amateur photographer Hart Preston who got the pictures of the trip for Life.

As you can see from the photo above (and from several other photos where it was visible), Parker brought with him a portable radio, which the magazine attributed as being one of the secrets of his success. In addition to the radio, Parker brought an electric razor which he used daily. He also bathed almost every day, resulting in a clean-cut appearance.

According to the magazine, the radio was the inspired touch. Drivers would ask Parker about it, made conversation about it, and found themselves persuaded to take him along.

Drivers were eager to talk about themselves and give their opinions about politics. By the time he reached New York, all drivers thought that Roosevelt should run again, but only a third said they would vote for him. Most were in favor of staying out of the war, and almost all of them thought it had been a shame to change the date of Thanksgiving.



1919 Wireless Receiver

1919OctRadioAmateurNewsA hundred years ago this month, the October 1919 issue of Radio Amateur News showed how to make this receiver (that is, a replacement for a headphone) for wireless use. It was said to provide a bit more volume than a standard headphone, allowing its use on the table, rather than strapped to the ear.

It consists of a phonograph reproducer attached to a steel piano wire held taut above a coil. The tightness of the wire, the number of turns of the coil, and the distance from the coil to the wire were subject to experimentation.

The cone was optional, but would produce more volume.

For more ideas on homemade speakers and headphones, visit our posts on
piezoelectric speakers, a homemade magnetic speaker, and homemade microphones.



Scout Signaling: 1939

1939OctBL2Eighty years ago this month, Chief Scout Executive James E. West penned this editorial in the October, 1939, issue of Boys’ Life, stressing to Scouts the importance of the skill of signaling.

He noted that signaling was included in the Scout requirements because it was “part of the equipment of an outdoorsman” and helped a boy to be “accurate, painstaking, and thorough.”

He began by recounting an episode that took place in Sequoia National Park during a raging forest fire. One crew was at work on a hill when they found themselves trapped by flames on all sides. Frantically, they began signaling with their signal flags for water and more men.

But everyone else in the region was busy fighting the fire and initially nobody noticed their frantic plea. Fortunately, however, another fire fighter had been a Scout, and the signals caught his attention. Out of a crew of sixty men, he was the only one who could read the message, but rounded up a crew to rescue his trapped colleagues, who were saved in the nick of time.

Also, during a flood in Zanesville, Ohio, the flood waters divided the town, and all telephone and telegraph lines were down. The first messages to get through were from Scout troops on the opposite banks of the river.

Another Scout saw a plane circling over his town, and noticed that it was flashing a light. Thanks to his knowledge of Morse Code, he made out the siganl “N-A-M-E.” The quick-witted Scout figured out that the pilot had lost his way. He got a large mirror, turned on the lights of an automobile, and flashed the beam of light upward, sending the name of the town. The pilot answered, “T-H-A-N-X.”

The tradition of Scouts learning signaling continues with the Signs, Signals, and Codes Merit Badge, which I counsel in the BSA Northern Star Council.  I have more information about the Merit Badge at this post and this one.  I also have links to advice from William “Green Bar Bill” Hillcourt.

If you know any Scouts who are interested in earning the Signs, Signals, and Codes merit badge, I will be counseling it at the North Star Scouting Museum in North St. Paul, MN, on Saturday, October 19, 2019.  For more information or to sign up, visit the museum’s website.