RF Cafe

A New Approach to Long-Distance Transmission

This story in the April 1955 issue of Radio & Television News might be the first public disclosure of Bell Telephone Laboratories' flexible waveguide design. Operating at 50 GHz, the new waveguide will replace hundreds of existing coaxial cables that can each carry only 600 telephone channels and two television channels. It can also increase the distance between amplifiers from 12 miles to 50 miles. Construction consists of a hollow flexible tube lined with a spiral winding of copper wire. Incidentally, the lower cutoff frequency for circular waveguide with a 2-inch diameter, as reported here, works out to around 1.8 GHz. I was skeptical about the claim of operation...

Carl & Jerry: Electrical Shock

In his usual manner, John T. Frye uses tech-savvy teenage experimenters Carl Anderson and Jerry Bishop to teach a lesson while writing a compelling saga. In this case Jerry gets "bitten" by house current while fiddling with a receiver chassis. Before certain safety measures were required by law, many electrical devices - radios, televisions, vacuum cleaners, shop tools, kitchen appliances, etc. - were sold with with either existing shock hazards or the potential for (no pun intended) a shock hazard in certain usage or failure modes. Before the advent of polarized two-pronged plugs and grounded 3-prong plugs, some devices presented hazardous voltage levels to the user by virtue of a direct connection to exposed conductive (metal) surfaces. In this instance, under normal operational conditions with the chassis installed in its wooden case and plastic or phenolic control...

All About Ovonics

Stanford R. Ovshinsky is a name with which most people are probably not familiar, even though some of his 400+ patented inventions can be found in many products. The most notable is the nickel-metal hydride (NiMH) battery. He also delved deep into phase change memory and amorphous semiconductors. What caught my attention in this 1969 Radio-Electronics magazine article was the claim that use of an ovonic switch matrix in conjunction with red, green and blue (RGB) phosphor light sources could produce the world's first large screen, flat panel video display that would not require scanning electron beams or rear projection. History shows that the idea never came to market, probably due to a combination of technical, financial, and manufacturability issues. Ovonics (a portmanteau of "Ovshinsky" and "electronics") is still used in aspects of the alternative energy industry...

The Propagation of Short Waves

"Short waves," with their ability to support long distance communications under certain conditions, became a phenomenon in the late 1920s, and a market developed for converting commercial broadcast receivers to short wave receivers. Magazines at the time were full of advertisements for the devices. The particulars of short waves and the way they propagated in the upper atmosphere were not yet well understood early on. In fact, the government considered transmission frequencies above 1.5 MHz (≤200 meters) so useless that they assigned those bands to amateur radio operators. The presence of an electrically conductive layer, known as the ionosphere, was not verified until 1927 by Edward Appleton...

Are You Ready for CONELRAD?

Before the Emergency Alert System (EAS) was activated on January 1, 1997, which followed the August 5, 1963 activation of the Emergency Broadcast System (EBS), there was the 1951 implementation of the CONtrol of ELectromagnetic RADiation (CONELRAD). Born out of the Cold War era, CONELRAD was devised in order to not just provide timely forewarning of enemy nuclear and/or bomber and/or submarine-based attacks, but also to silence all commercial broadcasters whose transmitting installation could potentially be exploited as homing signals for the aforementioned bad guys. The Germans had used just such a scheme during the recently concluded World War II to knock out Allied radio stations. CONELRAD used designated "clear channel" installations whose super high power outputs would reach across the land to give warning to even remote areas...

All About Reed Relays

This April 1967 edition of Electronics World magazine featured a handful of articles covering different types of relays and circuits for controlling them: reed relays, time-delay relays, stepping relays, mercury-wetted relays, resonant reed relays, operate and release times, relay coil considerations, and more. Even with the advent of transistor switching, there are still many uses in modern circuits for electromechanical relays, so this material should prove useful. Links are provided to the other relay articles...

Electronics Inventors Quiz

Most of these matches of the devices and its inventor are pretty easy for people who have been around electronics for any length of time (well, not if the length of time is a day or two), but a couple just might stump you. This Electronics Inventors Quiz appeared in a 1963 edition of Popular Electronics magazine, so you won't be challenged with knowing the inventors of the LCD or MEMS devices, but neither will you have to know who came up with the abacus or the Archimedes screw (or who's buried in Grant's tomb)...

At Last - Some Different Toobs!

The April 1933 issue of the American Radio Relay League's monthly publication QST (Q-code for "general call to all stations") was chock full of gags, much to the delight of readers based on subsequent letters to the editor. The editors must have felt a need to alert readers that some of the material was not to be taken seriously since the Table of Contents lists them as being in the "April Fool Section." I have posted a few of them. As with so many of these vintage articles, being privy to the customs and equipment of the era is essential to "getting" the joke. I will refrain from spoiling these, but if you need some insight from an old guy (61 years in August), send me a note and I'll try to put them into perspective. One gag takes careful observation to notice, and you don't need gray hair to figure it out...

Comics from the March 1971 Popular Electronics

For a few years, Popular Electronics magazine ran an electronics-themed single-panel comic feature called "Parts Talk." Jack Schmidt was the artist for the series, and is evident by the "Thanks Joe Cox" on the page 49 comic, he must have used ideas for topics submitted by Popular Electronics readers. From today's perspective of grain-of-salt size surface mount components, the claim of "It's a small world," by that vertical-mount capacitor doing the talking is very dated. Compared to its previous generation of vacuum tubes and discrete components that needed to handle higher voltages and power dissipation, these through-hole printed circuit board (PCB) components are a small world. Another half a century from now, the need for discrete, off-chip components...

Value Engineering for the Electronics Industry

Some topics are timeless. This is one of them. The term "Value Engineering" is not so familiar these days, since ostensibly it was developed by General Electric back in the World War II era. Per Wikipedia, "Value engineering (VE) is a systematic method to improve the "value" of goods or products and services by using an examination of function. Value, as defined, is the ratio of function to cost. Value can therefore be increased by either improving the function or reducing the cost. It is a primary tenet of value engineering that basic functions be preserved and not be reduced as a consequence of pursuing value improvements ." This article from the August 1967 Electronics World was a good read then, and it is a good read today...

The Silent War: Electronic Spying

Ah, those were the good old days, when governments used their limited reconnaissance ability to spy on people, places, and things deemed to be a clear and present threat to the well-being of country. In 1964, during the height of the Cold War, collecting and interpreting communications data was still a very human-intensive chore, so assets were necessarily allocated based on highly strategic targets. Today, data collection collection, storage, and analysis is cheap and is done mostly unattended by humans until a red flag goes up. The possibility of a nuclear attack from the Union of Soviet Socialist Republics (U.S.S.R.) was a very real and even likely possibility. The strategic advantage of a first strike was immense, so it was to the world's advantage to monitor and react as quickly as possible. The Soviet Socialists liked to propagandize about being...

Carl & Jerry: Command Performance

Assuming that a couple creative teenage boys could get away today with electrifying weapons to dramatize a mock sword fight during a high school production of a Roman battle, you can be sure the suit of armor required by safety monitors would consist not of coats of mail, but coats of rubber and fire retardant material, fully sealing OSHA-approved goggles for eye protection, ear plugs, and electrical lineman's gloves. Offstage would be certified fire fighting professionals (formerly called firemen) and an emergency response crew specially trained in high voltage electrical contact with a hospital-style emergency room crash cart nearby...

TV X-Rays Are Back

Color television was a big hit with homeowners and was adopted fairly rapidly in the 1960s even considering the relatively high cost and low number of network color broadcasts in the beginning years. The enthusiasm underwent a severe reduction when word got out that large doses of x-rays were streaming out of the front of the CRT for sets that did not take precautions to prevent it (which was the majority of sets initially). The major cause was extremely high voltages applied between the electron gun and phosphorescent raster grid - in the neighborhood of 35 kV or more - when the high voltage regulator circuit malfunctioned. Note that even when everything was working properly, a small amount of x-ray radiation was emitted. The x-ray problem...

TV X-Rays (Again)

Here is the promised follow-up on yesterday's article, "TV X-Rays Are Back," from June 1969 issue of Radio-Electronics. This x-ray emission issue, whether legitimately a serious health problem or not, was a big deal and was hyped up by the news media the way cellphones causing brain cancer and laptop computers sterilizing men is done today. For a while it measurably affected the volume of color television sales. X-rays are a form of ionizing radiation (unlike microwaves which are not) and can thereby cause cancer by rearranging atoms and molecules. At the root of the problem was the extremely high acceleration voltage (HV) and beam current being used in the cathode ray tube (CRT). Potentials in excess of 25 kV generated the most harmful level of x-rays, so manufacturers redesigned sets to use lower voltages, and also incorporated...

Training Civilians for Wartime Radio Operating

There was a time when a sense of national pride accompanied an ingrained a desire to perform a civic duty, particularly when crisis or war was upon the country. Unlike today's environment of "rights" and entitlements promised by politicians without any authority in the Constitution, people volunteered to assist neighbors and friends for the good of not just their immediate neighborhoods, but of their country. Rationing was imposed on many goods by the government for the sake of the war effort, but most folks were more than willing to comply since nearly everyone had a son, father, uncle, or good buddy serving to defeat the Axis powers. Recall the scene in "It's a Wonderful Life," where George Bailey and family served as volunteers for the Red Cross, bottle and tire drives, and Civil Defense block wardens, while younger brother Harry flew bombers...