Monthly Archives: March 2015

Miss Miami Aviation, 1940

MiamiAviationSeventy five years ago, Scout Felton Fineannon of Troop 26, Miami, assists 19-year-old Miss Ruth Shelley as she hoists Old Glory to mark the opening of the All-American Air Maneouvers held in Miami. Miss Shelly had been named Miss Miami Aviation in a beauty contest in which she took a challenge to earn her pilot license and learn to fly a sea plane solo within a week.

She held the title for two years, during which time her photo frequently appeared in the papers. Years later, a schoolmate wrote to her and told her that one of those newspaper clippings kept him alive during World War II. In a letter written to her a half century later, he told her that the picture kept his faith alive during the darkest moments of the war. She died Mrs. Ruth Chenoweth in 2009 at the age of 89.



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WBBM and KFAB Synchronize Their Signals With a Piece of Lead Pipe

In 1928, WBBM in Chicago and KFAB, then in Lincoln, Nebraska, both operated on 770 kHz with 5000 watts.  And they both carried the CBS network at night.  They generally coexisted well, but there was a problem for listeners, mostly in Iowa, who were equidistant from the two stations.  Both stations would come in equally strong, but interfere with one another.  These listeners complained to CBS, and the two stations worked at solving the problem.

Eliminating any heterodyne (the squeal caused by two signals on very close frequencies) was an easy enough problem to solve.  The two stations simply needed to make sure that the transmitters were exactly on the same frequency.  But there was another problem.  The signals from the network came by telephone lines, and those signals travel at approximately the speed of light.   Since Lincoln was 500 miles further away from New York than Chicago was, the program reached Lincoln about 23 milliseconds later than it reached Chicago.  Therefore, the two stations weren’t transmitting the exact same program.  KFAB was sending out the program with an additional 23 millisecond delay.  (When a different phone line was used later, the delay grew to 35 milliseconds.)

This caused a problem for listeners in Iowa.  The signals from Lincoln and Chicago traversed the airwaves to Iowa in the same amount of time.  But since the Lincoln signals started with a built-in delay, the effect in Iowa was that the there was an echo effect when listening to CBS on 770.

The stations solved the problem in a number of ways.  First of all, WBBM paid KFAB to sign off at 10:00 PM, after the end of network programs.   After 10:00, WBBM had a clear channel as far west as its signal would go.  The two stations also coordinated their station ID’s so that one announcer was not talking over the other.  But the biggest problem to solve was the delay.  To solve the problem, WBBM had to delay the network feed.  With digital processing today, this would be a trivial problem to solve.  But in 1928, it was a major engineering challenge.

The WBBM engineers eventually came up with an electronic solution involving 19 stages of filtering, equalization, and amplification.  A series of filters, consisting of a capacitor and inductor, were carefully chosen.  Each filter attenuated one frequency range, but also introduced a delay.  Since they didn’t want the attenuation, the equalization was needed to restore the audio to its final form, and the amplification was needed to make up for the loss in the filters and equalizers.

But until that system was designed, WBBM engineers came up with a Rube Goldberg solution that worked amazingly well.  The speed of light is about 300 million meters per second.  But the speed of sound is about 1080 feet per second.  To generate the necessary 23 millisecond delay, sound would need to travel about 23 feet.  So the WBBM engineers procured a 23-foot section of lead sewer pipe, mounted a speaker at one end and a microphone at the other end.  The sound was simply fed through the pipe before going on the air.

The system wasn’t perfect, since echos from the microphone reflected back, adding a new echo effect, what they were trying to get rid of in the first place.  But this echo was solved by wadding fabric into the pipe.  Close to the microphone, this consisted of gauze.  Closer to the speaker, thicker material was needed.  Fabric from a pair of overalls belonging to one of the staff turned out to fit the bill, and they were stuffed into the pipe.

The result was a very high quality audio signal, with a dynamic range of 100-5000 cycles.  Eventually, broadcast standards called for slightly better audio, and the electronic system using filters was used.  But for a time, WBBM’s programming passed through 23 feet of sewer pipe before hitting the airwaves.



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Mobile TV Repair: 1955

This photo from 60 years ago shows someone doing a job that doesn’t exist any more, namely, TV repair. In particular, it shows Tempe, Arizona, TV serviceman Dick Ramos, owner of the three person company. In addition to himself, he employed an assistant who rode with him on the truck, and an office girl who staffed the shop downtown, taking phone calls and walk-in service requests. Ramos pointed out that it wasn’t necessary to hire a highly trained television repairman to staff the shop. “In a short time an intelligent office girl will know more about a television set than 95 per-cent of the customers she deals with.” Ramos contracted with a radio paging service to relay messages during the day, and he maintained an efficient operation. The truck contained a complete shop with a full array of test equipment, as well as a complete set of service bulletins.

GE Model HJ-1205 Short Wave Console, 1940

GEHJ1205This advertisement appeared in Life Magazine 75 years ago today, March 18, 1940.

It features the General Electric model HJ-1205 console, a twelve-tube model including a tuning eye tube. It features three bands, standard broadcast and two short wave bands, 2.3-7 and 7-22 MHz. It also have eight pushbuttons which can be preset to broadcast stations. The promised “golden tone” is delivered by dual speakers, the larger of which is 12 inches. Pictures of a nicely restored specimen can be found at the Radio Attic Archives.  More pictures and a schematic can be found at

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OSCAR III: 50th Anniversary


Fifty years ago, from March 9-27, 1965, the first two-way amateur satellite, OSCAR III, was in operation. The 16.3 kg spacecraft was launched on March 9 from Vandenberg Air Force Base, piggybacking with seven Air Force satellites. Over 1000 amateurs in 22 countries made contact through the satellite’s linear transponder, with both the uplink and downlink taking place on the 2 meter amateur band. Signals were received by the satellite on 144.1 MHz, and were retransmitted on 145.9 MHz. The downlink had a power of one watt, which was divided over the whatever stations were in the passband of the uplink frequency.

A beacon transmitter sending voltage and temperature readings was audible for several months. The orbit was nearly circular, with an altitude of 570 statute miles and an orbital period of 103.5 minutes.

OSCAR3The photo here shows Ed Hilton, W6VKP, and Don Norgaard, W6VMH, working on the satellite’s electronic package in Hilton’s garage. This photo is taken from the March, 1965, issue of Popular Electronics.  A summary of the mission and complete list of contacts made and calls heard during the spacecraft’s 250 orbits is also available online.

The TV-Typewriter: 1975 Computer Terminal


40 years ago, careful observers were probably anticipated that something like the Internet would sometime come to pass. For those early adopters, Radio-Electronics magazine carried plans for a terminal, which the magazine called the TV Typewriter II, since an earlier version had appeared in the magazine in 1973. Some of the chips used in the 1973 design, however, turned out to be unobtainium, and the 1974 model featured use of commercially available 74-series TTL chips. The plans included a keyboard (hence “typewriter”), and called for connection to a black and white TV for the display (hence “TV-typewriter”). The plans for the 1974 model, shown here, are found in the FebruaryMarch, and April, 1975, issues of the magazine.

The terminal had an RS-232 interface, and could communicate at 110, 220, 440, or 880 baud, or if a different crystal was used, 150, 300, 600, or 1200 baud. The terminal had two potential applications. First, the article noted, would be “data communications with computers. Combined with a keyboard, we have one of the fastest and most efficient means for an individual to communicate with a machine.” One example of a computer with which it could communicate would be the fledgling home computer described in the magazine’s July, 1974, issue.

Another, possibly more common, use for the TV-typewriter was also given: “Of course, if you don’t have or don’t want your own machine, you can always tie into a full size time-shared system, assuming you have access to one.”

ASR-33 at CHM.agr

This statement shows how the TV-typewriter foreshadowed the Internet. My first experience with computing involved one of those time-shared systems. In my case, I accessed the Minneapolis Public Schools’ timesharing system with the use of a 110-baud teletype machine, like the one shown here.  To use this terminal, we dialed the phone number of the timeshare system computer, placed the telephone receiver into the acoustic coupler modem, and after logging in we were able to do things such as write short basic programs. Later on, other systems such as the Minnesota Educational Computing Consortium‘s MECC-MERITTS system, which also included a rudimentary chat function.

Of course, accessing such a system required having physical access to a terminal, which nobody other than the school owned in those days. Something like the TV-Typewriter would have been an incredible luxury for those of us interested in the proto-internet offered by the timesharing systems.

Many of us back in those days figured out that it was just a matter of time before something like the Internet came into being. However, most of us were wrong in one regard. We believed that online computing would follow the model of those timeshare systems: There would be a big computer somewhere doing all of the computing, and users would access it using a dumb terminal like a teletype machine or the TV-Typewriter.

In some respects, our predictions were borne out a few years later when CompuServe came along in the late 1970’s and early 1980’s. It was way out of my price range, at about $5 per hour (a rate at which it would cost about $20 to download the entire contents of a daily newspaper). But since I worked for Radio Shack, which was one of its primary sellers, I did have limited access and was able to use it to read the handful of newspapers online, get aviation weather, and even access the early chat server. There was even something called “Email,” a registered trademark of CompuServe. It was still out of my price range, and I never even sold a single subscription, but I realized that it was the future of computing.

Except I was still wrong on one detail. I still assumed that online content would be delivered the way that CompuServe was doing it: Individual users would use a dumb terminal to call a big computer somewhere that delivered the content. The 1981 video below is a newscast about the early days of CompuServe. It also makes clear that this is the model: Once a day, the newspaper in San Francisco programs into a computer in Columbus, Ohio, the contents of the daily paper.

Most of us believed that was how it would work, and we were wrong. We probably could have figured this out, because to access that computer in Columbus Ohio, we weren’t exactly using a dumb terminal. We were using a computer (at that point, the TRS-80 Model 100). By today’s standards, the computer didn’t have much computing power. It had 8 kB memory and ran at 2.4 MHz. But that computing power was doing only one thing: Emulating a dumb terminal. The computing power wasn’t being used, other than to duplicate the functions of the 1975 TV-Typewriter.

By the early 1980’s, the first computer bulletin board systems (BBS’s) were starting to appear. They esentailly followed the same model as the early timesharing systems and CompuServe. The only difference was that they were much smaller systems, generally run by hobbyists. But the end user still called up the “big computer” with a dumb terminal. The real origin of the internet is best seen in a development that took place a few years later, when BBS systems began to be linked up as FidoNet.  FidoNet was developed starting in 1984. Users would still call in to a single local BBS. But at night, when the phone rates were low, those BBS’s would communicate with one another and transfer mail, discussion posts, and files. While the end user would still interface only with one local “big” computer, the information he or she was reading actually originated on some other computer. In other words, the information was no longer centralized in Columbus, Ohio. The absence of one computer from the larger network would hardly be noticed. For home users, the Internet really began in 1984 when FidoNet allowed them to access information globally from a dumb terminal. Most users of these BBS systems were using computers with some computing ability. I doubt if too many TV-Typewriters were being used in 1984. But the TV-Typewriter, assuming that someone got one working in 1975, would have been perfectly adequate to the task.

The TV-Typewriter by itself was still missing one important component. It did not include the modem. To use it with a timesharing system (or a few years later, with CompuServe or FidoNet), the builder would also need to construct a modem to get those 110 baud signals into the phone line.

For those who built the TV-Typewriter, they probably had some inkling that there would be an Internet someday. They had the details wrong. They probably thought that there would be a big computer in Columbus Ohio to which they would connect. But they probably had some of the basic ideas.

Making Resistors in 1925

1925ResistorNinety years ago, the March 1925 issue of Radio Broadcast shows how resistors were made. This worker, at the Chicago radio show, is running a precision machine capable of producing resistors ranging from 3 to 700 ohms. The wire was wound automatically, very accurately and quickly.

Kathleen Parkin, 6SO/6BP, Radio Pioneer

6SO1916A hundred years ago, the young lady shown here, 6SO, was burning up the ether of the West Coast.

Shown here in the August 1916 issue of The Wireless Age is Miss Kathleen Parkin of San Rafael California. which the article identifies as one of the youngest girl wireless operators in the world. She was fifteen years old and held a first grade commercial license, having gained her knowledge of radio in her brother’s station where, as she said, “I spent every minute of my spare time, and often helped him make his instruments.” She constructed, without assistance the 1/4 kilowatt transmitter shown here, and was in the process of making a rotary spark gap and a receiver with vacuum tube detectors. At the time, she was using a galena detector, but successfully receiving up to 1000 miles.

According to Wikipedia, her full name was Gladys Kathleen Parkin, and she was born in San Francisco in 1901, and moved to San Rafael after the 1906 earthquake. She received her amateur license at the age of 9 (in about 1910), and she died in 1990.

In the 1923 call book, she is listed as holding the call 6BP. However, in the 1938 call book,
there’s no listing for W6BP.  I was unable to find any later history about Miss Parkin. If you know more about this wireless pioneer, please add a comment or contact me.

One Dollar, One Tube Radio, 1935


Eighty years ago this month, March 1935, Radio Craft magazine featured this one-tube broadcast radio that could be built for a dollar. The only manufactured radio part was the type 30 tube, which ate up 75 cents of the budget. Everything else was scrounged from household goods. The author reported receiving a station in Dallas, 1500 miles away from his location, the first night.

The two fixed condensers were made of tinfoil and waxed paper. The filament condenser consisted of 36 feet of 36 gauge wire wound on a spool. The grid leak condenser, which would probably be about 1 megohm, consisted of a pencil mark on a piece of wood. The tuning condenser consisted of two metal plates separated by celophane. The tuning coil was home wound on a cardboard form, and the tube socket was four paper clips.

The diagram of the completed receiver is shown below.


400 Foot Towers at Great Lakes, Illinois, 1915

ChicagoTribune03111915One hundred years ago today, March 11, 1915, the Chicago Tribune reported the completion of the third largest radio tower in the world, one of the two 400 foot towers at the naval training station at Great Lakes, Illinois. The paper reported that the station would be able to establish communications between both coasts, Alaska, and the Canal Zone.

The Chicago antenna’s height was bested only by the Eiffel Tower and the navy station at Arlington, Virginia. To mark the completion, the flag flown by the U.S.S. Chester at the Battle of Vera Cruz was unfurled from the structure. The commandant of the naval station had previously commanded the Chester at Vera Cruz.