The Renode - A New Gridless Tube

Competition amongst countries and businesses existed long before the advent of radio receivers. Here is an interesting story which demonstrates how international politics and corporate policies has been part of the electronics industry since its inception. In order to circumvent what were considered to be outlandish patent licensing fees, Danish engineer Carl Arne Scheimann Jensen developed a new "gridless" type of vacuum tube (aka valve) which was called the "Renode." Rather than using a screen grid in the path between the cathode and plate, the Renode employed two sets of beam concentrator and deflector plates on either side of the electron beam's path to modulate the conduction. According to measurements it provided a slight improvement in both linearity and selectivity...

Steerable Beam "Leaky" 6G Chip

"Sixth-generation wireless networks, or 6G, are expected to achieve terabit-per-second speeds using terahertz frequencies. However, to harness the terahertz spectrum, complicated device designs are typically needed to establish multiple high-speed connections. Now research suggests that advanced topological materials may ultimately help to achieve such links. The experimental device the researchers have made, in fact, achieved 72 gigabits-per-second data rates, and reached more than 75% of the three-dimensional space around it. Current solutions typically achieve only one or two of these features at a time and often rely on complex antenna arrays or mechanical steering..."

RF & Microwave Companies Crossword Puzzle

This week's RF & Microwave Companies crossword puzzle includes the names of all my current advertisers and a few others that will be familiar to many of you. These kinds of puzzles take a particularly long time to create because of needing to force words into certain positions. That leaves the software with fewer options for fitting the other words. All the words in RF Cafe crossword puzzles are relevant to engineering, science, mathematics, etc., stored in a hand-built (over more than two decades) lexicon of thousands of terms and clues. Enjoy...

Clairvoyant Dr. Fox

Mystery stories were broadcast on radio stations in the days before television - and for quite a while after TV was available for that matter. Families gathered around the living room radio set in excited anticipation of the next adventure of shows like "The Shadow," "Amos 'n' Andy," "Tales of the Texas Rangers," "Dragnet," and "The Green Hornet." During that era, it was common also for electronics magazines, which focused largely on radio communications, to experiment with printed dramas that had a radio-centric theme. Here is the first of a series tried by Radio-Craft magazine in the late 1930s. A couple decades later the Carl & Jerry adventures were run in Popular Electronics, but other than that I don't recall seeing a lot of these things...

Crystal Diodes in Modern Electronics

Diode characteristics and their applications have not changed fundamentally since this article was published in 1952. Sure, the die are smaller, power handling and frequency range has increased, package styles are greatly expanded, and the cost per unit is way down, but if you are looking for some basic diode information, you will find it here in this 4th installment of a multi-part series in Radio & Television News magazine. Don't let the vacuum tubes in schematics scare you off and think that it makes the story irrelevant for today's circuits. For purposes of illustration substitute a transistor's collector (or drain) for the tube's plate, a transistor's base (or gate) for the tube's screen grid, and a transistor's emitter (or source) for the tube's...

Drones - Put R/C into War Games

The term "drone" these days for most invokes the image of a little plastic spider-looking thing with propellers mounted at the ends of the arms - usually with a toothless bumpkin at the controls. Those same people often think drones are relatively new devices. People with a just a little more information automatically classify all radio control (R/C) models, be they traditional fixed-wing aircraft or helicopters, as drones. Pilots of the aforementioned models are even likely, per observers, to have all their teeth and bathe regularly. I happen to be one of the latter type R/C modelers and while I no longer possess all 32 teeth I had at birth, I do bathe regularly. Drones have been around since World War I where they were used for target practice by ground-based mark...

Publicity Means Sales!

"If you have dark eyes and blonde hair. and are under 30, you're due for some easy squeezing. Milligan's Appliance Center, 84 Main Street, is giving every girl between 16 and 30 who has these striking features a newly patented orange squeezer, to introduce the new item ... Note: Any traces of recent peroxide rinse will disqualify applicants." That is advertising copy offered as an example effective promotional material in a 1947 edition of Radio News. My first reaction was to think how something like that would never fly today, but then I wasn't so sure. It seems there must be anti-discrimination laws in this "offend nobody" climate today...

Radio Training Association of America Advertisement

Imagine having a serviceman of any sort arrive at your house, fix your problem, and present you with a bill of $6 - parts included. He would walk away satisfied that he had done a good job and was well compensated for the work considering the effort invested in training and qualification. $6 in 1932, per the Bureau of Labor Statistics' Inflation Calculator is worth $135.97 in 2015 money - that's a cheap service call even in today's economy. Further, the $14 stated as a day's earnings is $317.26 in 2025, which equates to 50 (work weeks/year) x 5 (days/week) x $243.86 (/day) = $79,315 (/year) - not too shabby. Just between you and me, that's more than I'm currently making per year running RF Cafe...

Thanks to Aegis Power Systems for Continued Support!

Aegis Power Systems is a leading supplier of AC-DC and DC-DC power supplies for custom and special applications. Aegis has been designing and building highly reliable custom power supplies since 1995. They offer a complete line of switch mode power supplies and power converters for a variety of markets including defense, industrial, aircraft, VME, and telecom. Supports military, aircraft, EV, telecom, and embedded computing applications. Design and manufacture of custom power supply solutions to meet each customer's exacting specifications. Please visit Aegis Power Systems today. Manufactured in the USA.

Oscillator Quiz

Oscillators were never my forte. My biggest exposure to oscillators was unintentional oscillations in amplifier circuits ;-( .  This Oscillator Quiz, published in the November 1962 issue of Popular Electronics magazine, would embarrass me if I attempted to complete it. Therefore, I will simply state that I highly regard your oscillator prowess if you do better than 50% on it. I guessed correctly at a couple of the more familiar circuits, but cannot even make an educated guess at most of them. Don't let the presence of vacuum tubes scare you off; mentally replace them with a FET and move on...

"Sayville Once More"

These letters represent an unfriendly exchange between The Electrical Experimenter editor Hugo Gernsback and Dr. K.G. Frank, of the Telefunken System of Wireless Technology, of Germany. Gernsback correctly accused Dr. Frank of engaging in espionage for Germany and against the United States of America, during World War I at a time we were not officially at war with the Axis powers. He was arrested and interred for the duration of the war for sending out "unneutral messages" from the broadcast station at Sayville, Long Island, New York. See "Radiobotage" in this month's (September 1941) editorial...

DIY Stratosphere Pico Balloon

"There's an interesting development in amateur ballooning: using so-called superpressure balloons, which float high in the atmosphere indefinitely rather than simply going up and up and then popping like a normal weather balloon. Superpressure balloons can last for months and travel long distances, potentially circumnavigating the globe, all the while reporting their position. You might imagine that an undertaking like this would be immensely difficult and cost thousands of dollars. In fact, you can build and launch such a balloon for about the cost of a fancy dinner out. You just have to think small! That's why amateur balloonists call them pico balloons. The payload of a pico balloon is so light..."

Radar Engineering Crossword

Many of the words in this week's crossword puzzle pertain to radar engineering. All the rest of the words are related to technology, engineering, science, mathematics, aeronautics, ham radio, chemistry, etc. There are no names of Hollywierd actors, shoe designers, or romance novel titles. I will be glad to create a special edition crossword for your newspaper, newsletter, etc. Enjoy...

Mac's Radio Service Shop: Safety in Servicing

It's time to gather 'round for another story about fictional radio service shop owner Mac McGregor and his trusted sidekick technician, Barney. In this episode, an errantly wired bypass capacitor on a chassis from one of the old AC/DC radio sets caused Mac to get a 300-volt wakeup call when his hand brushed against it. After explaining the situation to Barney and apprising him of the danger it poses to an owner who unwittingly sticks his/her hand into the back of the cabinet, Mac lists a few other common dangers to watch for. Radios that ran on either AC or DC power were very common back in the early days because there were homes and businesses that had both type systems wired in to the premises - in part due to the famous battle between Thomas Edison's preferred DC electrical distribution system and Nikola Tesla's preferred AC electrical distribution system. Another reason for DC compatibility was that prior to the Rural Electrification Act of 1936, many...

Editorial: Radiobotage

An incredibly glaring example of the famous admonishment* that those who ignore history are condemned to repeat it, Radio-Craft editor Hugo Gernsback wrote in May of 1941, a full half year before the United States of America officially entered World War II, about how current conditions regarding domestic commercial radio broadcast stations were likely being used by German agents to send coded messages to offshore vessels (ships, submarines, and aircraft). In example, he cited, amazingly, an article he himself published in 1915 in The Electrical Experimenter accusing Dr. K. G. Frank, of the German Telefunken company, of conducting spy operations from the Sayville, NY, station on Long Island...

Crystal Receiver with Transistor Amplifier

Considering that not much more than a year before this article was written that the transistor had been invented, it is impressive that already Raytheon was producing a commercially available CK703 "crystal triode." That nomenclature was a natural extension of the preceding crystal diode already being widely adapted in circuit design. If you have wondered how the transistor schematic symbol came to be as it is, you will learn why here where the emitter and collector symbols actually both have arrows on the ends that contact the base, indicating the "point contact" physical arrangement of the semiconductor junctions. Shortly thereafter the arrow on the collector port was eliminated, primarily, I suppose to avoid confusion when the E, B, and C labels are not present...

2D Transistor Transforms Logic, Power Devices

"CDimension recently unveiled a technology that enables conventional semiconductor fabs to use ultra-thin semiconductor materials to manufacture vertically integrated arrays of extremely small, fast, and efficient "2D" transistors. It has the potential to change what's possible for both digital and power devices. According to the company, it's already helping several chipmakers explore how to apply their technology to produce digital and analog ICs that offer dramatically higher logic densities, operating speeds, and energy efficiency..."

Radio Service Data Sheets

Here are three more Radio Service Data Sheets added to the online archive. As mentioned many times in the past, I post these for the benefit of hobbyists looking for information to assist in repairing or restoring vintage communication equipment. These particular radio models - Emerson Model 20A and 25A, Pilot Model B-2, General Electric Model K-40-A - were featured in a 1933 edition of Radio-Craft magazine...

Networks for Television

Nationwide commercial television broadcasting companies wasted no time stringing coaxial cable and microwave towers from sea to shining sea once the NTSC format standard was adopted and manufacturers had spooled up production after World War II. Adoption of cable services was slow because a fee was involved, but once purely cable channels started being added the perceived value increase convinced consumers to open their wallets. Eventually cable eclipsed over-the-air broadcasts for all but extremely rural areas that were not serviced by cable. Along came satellite TV to take care of filling that void. Once a small, inexpensive, unobtrusive Ka-band antenna replaced the huge S-band backyard parabolic dishes and subscription prices dropped significantly, suburbanites and city dwellers picked it up. Soon, cable companies were feeling the pinch as their customer bases shrunk. Not ones to sit...

Oscilloscope Quiz

A lot of RF Cafe visitors might not be familiar with some of the electronic waveforms presented in this Oscilloscope Quiz by Popular Electronics magazine's ultimate quizmaster, Robert Balin. The shapes are recognizable to anyone who has done a lot of design, troubleshooting, testing, or alignments on analog circuits. Electronics repairmen were intimately familiar with these - and much more complex - waveforms. Modulation of the z-axis is especially cool as it varies the intensity of the waveform. I always roll my eyes when, back in the day, a laboratory or medical facility in movies or on TV had an oscilloscope display with a Lissajous pattern writhing on the display...

SpaceX Shifts Focus from Mars to Moon

"SpaceX is putting its longstanding focus of sending humans to Mars on the backburner to prioritize establishing a settlement on the Moon, founder Elon Musk said Sunday. The South Africa-born billionaire's space company has found massive success as a NASA contractor, but critics have for years panned Musk's Mars colonization plans as overambitious. The move also puts Musk in alignment with U.S. President Trump's shift away from Mars. "For those unaware, SpaceX has already shifted focus to building a self-growing city on the Moon, as we can potentially achieve that in less than 10 years, whereas Mars would take 20+ years. Difficulties in reaching Mars include the fact that "it is only possible to travel to Mars when the planets align every 26 months..."

Hands That See: NY Institute for the Blind Prepares Students for Ham License

Life for the blind has always been fraught with obstacles that we who can see will never be able to fully appreciate. Society has come a long way in accommodating the special needs of those with no or severely reduced eyesight. Recent news stories report of experiments with electronic implants that use implants set into the eye and couple somehow with the retina to send image information to the person's brain. While in no way close to being able to be called sight, it has at least allowed the guy or girl with training to detect and avoid obstacles based on changes in scenery shading. We are probably a century away from true bionic vision, incremental improvements will thankfully improve the lives of our thusly challenged brethren. This article from a 1947 edition of Radio News reports on efforts made by the New York Institute for the Educations of the Blind to make amateur radio...

New! everythingRF Magazine

everythingRF, a long-time supporter of this website, is now, in addition to publishing e-books, putting out an e-zine which provides some insightful content, interesting products and expert interviews within the RF & Microwave industry. Vol. 4, now available, includes articles on Next Gen Adjustable Q-Band Gain Equalizers, Earth to Orbit:The Important Role of Antennas in NTN, Benefits for Phased Array Systems Through SM Components, as well as product features, upcoming industry events, and more. Download it now.

Mac's Radio Service Shop: Barney Talks A.C.-D.C.

Have you ever heard of a "globar" resistor? They have been around since the early days of radio and were used, among other things, to protect vacuum tube heater elements from burning up due to high inrush current when first turned on. Globars have a negative temperature coefficient (NTC) of resistance so that, opposite of standard carbon and metal film type resistors, they exhibit a higher resistance when cold than when hot. Mac and Barney discuss their use in this episode of "Mac's Radio Service Shop." You might be more familiar with the name "thermistor" for such devices, but globars are unique elements in that their construction from non-inductive ceramic material makes them useful at high power levels and high frequencies. Globar appears to now be owned by Kanthal (aka Kanthal Globar). Interestingly, Keysight Technologies...

Transistors: Types & Techniques

Louis Garner was the semiconductor guru for Popular Electronics magazine in the 1960s when he wrote this article attempting to demystify the proliferation of over 2,000 transistor types. He devised a "transistor tree," tracing evolution from the obsolete point-contact transistor - unstable with high gain but noisy - to advanced designs balancing cost, frequency, power, and reliability. It covers pnp and npn basics, then details processes: grown-junction (inexpensive, good high-frequency); meltback diffused (similar, better response); alloyed-junction (popular for power); surface-barrier family (SB, SBDT, MA, MADT; excellent high-frequency, low voltage); post-alloy-diffused...

• Global Trade Holds Its Ground

• FCC "Supercharge" Wi-Fi in 6 GHz Band

• Legacy Memory (DDR2, 3, 4) in Demand but Scarce

• 2026 is Year of 6G Slop

• FCC to Exempt Amateurs from Foreign Adversary Reporting

• Continuing Your Professional Education in 2026

The RF Cafe Homepage Archive is a comprehensive collection of every item appearing daily on this website since 2008 - and many from earlier years. Many thousands of pages of unique content have been added since then.

Women Radio Commandos

"Those who cannot remember the past are condemned to repeat it." That line from George Santayana's The Life of Reason: Reason in Common Sense always comes to mind whenever I see articles from vintage publications about how people at the time were being forced to defend their ways of life from maniacal would-be dictators who marshaled armies of like-minded crazies to invade and attempt to subdue other countries and/or citizens within their own borders. It seems after a generation or two of comfortable, relatively safe existence, the collective guard is lowered and the hard-lessons from history are forgotten or subversively erased from memories. This particular 1944 Radio News magazine article tells the story of women of European Allied nations - in particular Polish women - taking up arms against Axis powers (Germany and Italy) during World War II. Part of the survival effort included learning to operate and service communications equipment in order to provide surveillance and security both on the battlefield and in helping countrymen escape the incursion. Some were captured...

National Union Radio Corporation Promotion

National Union Radio Corporation was ahead of its time in terms of hiring women engineers. Admittedly, they and all other manufacturers were dealing with a shortage of male engineers due to the ongoing need by the military for fending off the scourges of fascism, Nazism, communism, socialism, and all the other "isms" of the day that threatened to overtake the world. However, they should receive due credit for going out of the way to promote the sciences as careers for the fairer gender. The advertised positions required the successful applicant to have earned a bona fide degree in physics, electrical engineering, chemical engineering, mechanical engineering, mathematics or chemistry. According to a page on the Harvard Business School website, "The National Union Radio Corporation was incorporated in September 1929 to acquire...

Mac's Service Shop: How It Started

Mac's staff service technician, Barney, asked a great question when he mentioned that Pittsburgh radio station KDKA made the country's first commercial broadcast in 1920: "Who was listening?" It is a reasonable question since prior to the beginning on commercial radio broadcasts there would have been no reason for there to have been a lot of people to own a radio for receiving commercial broadcasts. The answer, of course, is that there were plenty of multi-band radios in homes and businesses for listening in on shortwave broadcast from around the world - a very popular pastime in the era. Just as today we are bombarded with admonitions to not stare at computer monitors or cellphone screens for too long lest we suffer near-sightedness or worse, radio listeners of yore who used headsets were told, "Youths of this generation will never have as protruding ears as some of their older brothers." I suppose...

The Declaration of Independence...

...because it is important to remember what is actually in it - not just what the Public Schools teach about it::: "In CONGRESS, July 4, 1776. The unanimous Declaration of the thirteen united States of America, When in the Course of human events, it becomes necessary for one people to dissolve the political bands which have connected them with another, and to assume among the powers of the earth, the separate and equal station to which the Laws of Nature and of Nature's God entitle them, a decent respect to the opinions of mankind requires that they should declare the causes which impel them to the separation. We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness..."

The Moon: We Look Before We Leap - Ranger 6

Congress was breathing hard down the neck of NASA while Ranger 6 was being prepared for its surveillance mission to the lunar surface. In 1962, Ranger 3, the first to carry a TV camera, went into orbit around the sun after missing the moon. Ranger 4 (dubbed "Brainless I") impacted the moon but did not send back any data. And Ranger 5 lost power after launch and missed the moon by about 450 miles. Time was running out to collect data for use in fulfilling the challenge issues by President John F. Kennedy on May 25, 1961, to "...commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth." That challenge was successfully met by the Apollo 11 mission partially on July 21st, 1969 by landing Neil Armstrong and Buzz Aldrin on the moon...

Electronic Crossword Puzzle

This "Electronic Crossword" appeared in the September 1958 issue of Radio & TV News magazine. Its creator, John Gill, designed specialty theme crossword puzzles for many other editions of Radio & TV News and Electronics World (see the big list at the bottom of the page). He considered this crossword to be a "fooler" because he claims to include many "unusual definitions and a number of obscure words which you will have to work around if your vocabulary of 'exotic words' is rusty." It really doesn't seem so difficult to me, and anyone used to working my custom RF Cafe Crosswords will have no problem with it.

How to Solder

Proper soldering is almost as much of an art form as it is a technical skill. Having been through numerous soldering classes in my career, starting with electrical vocational courses in high school, then again in USAF technical school, and other times while working as a technician and engineer, I always exercise care in making solder joints. Proper preparation - including both tinning of mating surfaces and a means to prevent the joint members from moving during cool-down - is of utmost importance for assuring a nice, smooth, shiny joint with just the right amount of solder. Lead-free solders do not tend to produce the level of shininess as do the good old 60-40 type tin-lead solders, but you can still make a nice looking joint. This might be more information than you want to know about me, but I even strive for perfection in solder joints in copper pipes and fittings used in plumbing work...

Capacitor Know-How Simplifies Electronic Projects

Filtering, timing, coupling, and energy storage are the most common uses for capacitors (not to mention their use in electronic component sculptures). Metallized paper or plastic, plastic film, mica, ceramic, electrolytic, and a few other capacitor types have been around for a long time, with newer formulations of electrolytics providing higher charge storage density, lower leakage, greater stability, lower cost, wider operational temperature ranges, more robust construction, etc. We now have supercapacitors that...

Crosley Model 1316 (167 Console)

In the early days of radio, it was common for manufacturers to sell the electronics chassis separately from the cabinet, as well as selling a chassis / cabinet combination. Even as late as in 1941, the Crosley 03BC radio I have was a custom wooden console sold for accepting electronics from the 02CA electronics. I have never been able to find an advertisement where Crosley sold the 03CB as an integrated set, although I have seen ads for the cabinet. This Crosley Model 1316 chassis was evidently supplied in an optional Model 167 console cabinet, as presented in a 1936 issue of Radio-Craft magazine. A Web search turned up other Model 167 cabinets of both the "tombstone" and "cathedral" design. Did the Crosley numbering system top out at 167 for a while?

Reverse Current Keeps Ferry Afloat

A news story with a title about a boat and reverse current is more likely to be referring to water flow in a river or stream than about electrical current in a conductor. Having grown up in a neighborhood next to a tributary of the Chesapeake Bay, I spent quite a bit of time around boats, both large and small. Salt water is particularly destructive to metal hulls due to cathodic corrosion, exacerbated by the salt water's conductivity. While working as an electrician in the 1970s, I installed electrical supplies for a few dockside cathodic protection system that probably functioned like the one described in this 1965 issue of Popular Electronics magazine. The principle is fairly simple whereby anodes are placed in the water around the hull and a counter-current is induced...

Promote Your Company on RF Cafe

Banner Ads are rotated in all locations on the page! RF Cafe typically receives 8,000-15,000 visits each weekday. RF Cafe is a favorite of engineers, technicians, hobbyists, and students all over the world. With more than 17,000 pages in the Google search index, RF Cafe returns in favorable positions on many types of key searches, both for text and images. Your Banner Ads are displayed on average 225,000 times per year! New content is added on a daily basis, which keeps the major search engines interested enough to spider it multiple times each day. Items added on the homepage often can be found in a Google search within a few hours of being posted. If you need your company news to be seen, RF Cafe is the place to be...

RF & Electronics Stencils for Visio

With more than 1000 custom-built stencils, this has got to be the most comprehensive set of Visio Stencils available for RF, analog, and digital system and schematic drawings! Every stencil symbol has been built to fit proportionally on the included A-, B-, and C-size drawing page templates (or use your own page if preferred). Components are provided for system block diagrams, conceptual drawings, schematics, test equipment, racks, and more. Page templates are provided with a preset scale (changeable) for a good presentation that can incorporate all provided symbols...

TV/FM Antennas Getting Bigger and Better

Take a look at the variation in antenna design in the 1960s as presented in Radio-Electronics magazine. There was a boom in television and FM radio happening at the time, and antenna manufacturers were coming out with great new designs that promised to squeeze out that last little bit of signal reception and interference rejection. While fundamentally most of the antennas featured the standard array of straight, constant diameter reflector and radiator elements, many also incorporated fancy flat metal patches, spirals, and what resemble modern printed elements without the substrate. My guess it was mostly a combination of marketing hoopla and an effort to avoid patent infringements. There are not many TV and FM radio antenna models available today, but those that are generally don't have all the extra features. Some of the modern compact TV antennas made for receiving digital signals sport some fancy stuff, but they are fundamentally log periodic or Yagi design. Ham antennas typically do not have all the extra gimmicks, either. Aside from that, I have to acknowledge the amount of effort that went into illustrating all 30 of these antennas. A EM analysis of each using the latest modeling software...

November 15th Electronics Engineering Crossword Puzzle

For the sake of avid cruciverbalists amongst us, each week I create a new crossword puzzle that has a theme related to engineering, mathematics, chemistry, physics, and other technical words. As with all RF Cafe crossword puzzles, this November 15th Electronics Engineering crossword puzzle contains no names of politicians, mountain ranges, exotic foods or plants, movie stars, or anything of the sort unless it/he/she is related to this puzzle's technology theme (e.g., Hedy Lamarr or the Bikini Atoll). The technically inclined cruciverbalists amongst us will appreciate the effort. , movie star unless he/she was involved in a technical endeavor (e.g., Hedy Lamarr)...