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Variable-Capacitance Diodes

Variable-Capacitance Diodes, July 1969 Electronics World - RF CafeIt appears that maybe Abraham Lincoln had a son who was an electrical engineer working at Motorola Semiconductor back in the 1960's. Put glasses on Honest Abe (I did) and author Irwin Carroll's a spitting image of the Great Emancipator. Seriously though, this article is a great introduction to the fabrication and use of variable capacitance (aka varicap and varactor) diodes. They have been - and still are - used widely for electrically tunable oscillator and filter circuits. Topics such as temperature and figure of merit ("Q") are discussed as well. This edition of Electronics World ran a series...

Anatech Electronics July 2025 Newsletter

Anatech Electronics July 2025 Newsletter - RF CafeSam Benzacar, of Anatech Electronics, an RF and microwave filter company, has published his July 2025 Newsletter that, along with timely news items, features his short op-ed entitled "3GPP Release 20 Gets Us Closer to 6G." In it, he states, "One of the most significant areas of emphasis in Release 20 is integrating artificial intelligence (AI) and machine learning into the radio access network (RAN) and the core network." I have seen numerous news items in the last few months reporting on the melding of AI and network communications. This type of AI "intelligently" controls the global and local systems by optimizing traffic flow via real-time tower and control center analysis. A major feature is device-to-device (D2D) communications that can bypass the network...

Solid-State Scene: IC Comparators and Op Amps

Solid-State Scene: IC Comparators and Op Amps, May 1973 Popular Electronics - RF CafeIt is hard to imagine a time when integrated circuit (IC) comparators were a big deal, but as recently as 1973 when this article appeared in Popular Electronics, they were new to a designer's bag of tricks. Prior to an IC solution, comparators needed to be constructed from opamps and a handful of peripheral biasing components. As with other integrated circuits, not only does the overall price go down, but so does circuit board real estate, cost, temperature variability, and electrical parameter variance between devices. The first comparator circuit I remember designing was a temperature sensor that went in an oven used for curing the potting...

Mac's Service Shop: Servicing Without Service Data

Mac's Service Shop: Servicing Without Service Data, February 1974 Popular Electronics - RF CafeHere is an area of electronics that will be foreign soil to most Gen-Xers and Millennials - troubleshooting your malfunctioning radio, phone, television, garage door opener, kitchen appliance, etc. Admittedly, most modern devices are designed and priced to be replaced rather than repaired. Relatively cheap product replacement and service plans keep them going for a year or three until they are obsoleted by newer devices with whiz-bang additional features. However, there are many of us still around who are born to tinker and are too cheap to bear the thought of throwing something away before at least attempting to fix it. I have written often about how many...

MIT's 3D Chips Faster Energy-Efficienter

MIT 3D Chips Could Make Electronics Faster and More Energy-Efficient - RF Cafe"The low-cost, scalable technology enables seamless integration of high-speed gallium nitride transistors onto a standard silicon chip. Gallium nitride is an advanced semiconductor material that is expected to play a key role in the next generation of high-speed communication systems and the power electronics that support modern data centers. However, the widespread use of gallium nitride (GaN) has been limited by its high cost to incorporate it into standard electronic systems. To address these challenges, researchers from MIT and collaborating institutions have developed a new fabrication process that integrates high-performance GaN transistors..."

RF Cafe Engineering Crossword Puzzle

RF Cafe Engineering Crossword Puzzle w/Weekly Headlines February 25, 2018At least 10 clues with an asterisk (*) in this technology-themed crossword puzzle are pulled from "Tech Industry Headlines" column on the RF Cafe homepage (see the Headline Archives page for help). For the sake of all the avid cruciverbalists amongst us, each week I create a new technology-themed crossword puzzle using only words from my custom-created related to engineering, science, mathematics, chemistry, physics, astronomy, etc. Enjoy...

Please Thank IPP for Their Long-Time Support!

Innovative Power ProductsInnovative Power Products has been designing and manufacturing RF and Microwave passive components since 2005. We use the latest design tools available to build our baluns, 90-degree couplers, directional couplers, combiners/dividers, single-ended transformers, resistors, terminations, and custom products. Applications in military, medical, industrial, and commercial markets are serviced around the world. Products listed on the website link to detailed mechanical drawings, electrical specifications, and performance data. If you cannot find a product that meets your requirements on our website, contact us to speak with one of our experienced design engineers about your project.

Scope-Trace Quiz

Scope-Trace Quiz, March 1965 Popular Electronics - RF CafeJust yesterday I posted an article titled "Understanding Your Triggered Sweep Scope," that appeared in the May 1973 issue of Popular Electronics, so I figured this "Scope-Trace Quiz" would make a good compliment. It is from a 1965 issue of Popular Electronics. Driver circuits all include a sinewave source in parallel with a series resistor and diode, connected to the vertical and horizontal o-scope inputs. The resulting Lissajous waveforms resemble hands on a clock face thanks to the diode. Shamefully, I only scored 70%, but in my own defense I'll say I didn't take the time to draw them out on paper. Pay careful attention to the scope...

Airport Radar Could Help Aliens Spot Earth

Airport Radar Could Help Aliens Spot Earth - RF Cafe"Advanced alien civilisations could discover human life on Earth by picking up technosignatures given off inadvertently by civilian and military radar, new research shows. The study investigated how hidden electromagnetic leakage might look to extraterrestrials up to 200 light-years away if they had advanced radio telescopes like those on Earth. It also suggests this is how far humans would be able to look to spot extraterrestrials who have evolved to use a similar level of technology. Preliminary results revealed at the Royal Astronomical Society's National Astronomy Meeting 2025 in Durham show how aviation hubs such as Heathrow, Gatwick and New York's JFK International Airport give off clues to human existence..."

Test Bench: Build the Torture Box Environmental Chamber

Test Bench: Build the Torture Box Environmental Chamber, February 1974 Popular Electronics - RF CafeHere is a unique type of article from a 1974 issue of Popular Electronics. Author Ralph Tenny presents a poor-man's environmental test chamber constructed with a Styrofoam picnic cooler, a dry ice sump, a heater, a thermocouple, and a bunch of input/output ports for making electrical measurements. While working on my senior project at college - an electronic remote weather station - I needed to verify functionality up to 150°F and down to 0°F. Having the Torture Box would have been handy, but instead I used the kitchen oven and freezer with the interconnect cable mashed between the door gasket and frame. Unfortunately I don't have any...

Mac's Service Shop: Modules and the Technician

Mac's Service Shop: Modules and the Technician, January 1973 Popular Electronics - RF CafeThe transition from vacuum tubes to semiconductors, and from black and white to color televisions was in full swing by 1973. Accompanying the change in components was a re-thinking of the most effective and profitable method of manufacturing and servicing the new equipment. Modularization was thought to be key to future success even though production costs were slightly higher. Reliability improvements were already reducing the need for service calls and highly trained technicians who could troubleshoot failures down to the component level. Swapping out suspect modules with known-good modules, in Mac's words, results in "a quickly trained module swapper who knows only 'how' and not..."

Radio Measurements in Space

Radio Measurements in Space, May 1967 Electronics World - Airplanes and RocketsThe first thing I learned (or re-learned) in reading this article is that in 1967, "Hertz" had only recently been assigned as the official unit of frequency. According to Wikipedia, International Electrotechnical Commission (IEC) adopted it in in 1930, but it wasn't until 1960 that it was adopted by the General Conference on Weights and Measures (CGPM) (Conférence Générale des Poids et Mesures). Hertz replace cycles per second (cps). The next thing that happened was that I was reminded of how images such as the op-art tracing of antenna oscillation that are routinely generated today by sophisticated software, required huge amounts of setup time and trials to yield just a single useful and meaningful image using actual hardware...

The 8 Most Essential Types of PCB Vias

San Francisco Circuits has published a comprehensive guide on the 8 most essential types of PCB vias, helping designers, engineers, and procurement teams navigate the challenges of modern board manufacturing. This is a guide to the 8 different via types. As electronic devices continue to shrink in size while increasing in complexity, PCB vias play a critical role in enabling multi-layer interconnections, high-speed signal integrity, and thermal performance. The 8 main types of PCB vias each serves a specific function depending on the board's structure, component density, and electrical requirements...

Atomic Radiation: Measuring Techniques

Atomic Radiation: Measuring Techniques, July 1969 Electronics World - RF CafeThis is Part 3 of a series of articles on atomic radiation that appeared in Electronic World magazine in 1969. It deals with measurement techniques and equipment. Shippingport Atomic Power Station, the first full scale nuclear power plant in the U.S., went operational in 1957. It marked the dawn of a new era of electric power generation that was filled with grandiose predictions of limitless, non-polluting, dirt cheap power. Everything was going to be powered by electricity - air heating and cooling, lighting, automobiles, water heating. Atomic power was going to be a figurative and almost literal beating of swords into ploughshares as the destructive energy...

Engineering & Tech Headlines <Archives>

• FCC Power Shift Underway

• Global Foundry Market Sees Milder Dip in 2025

• U.S. Renegotiating Chips Act Awards

• Recalls Can Create a Multitude of Legal Problems

• Why ChatGPT's Essays Don't Fool the Experts - Yet

Electronics Themed Comics

Electronics Themed Comics, April 1944 Radio-Craft - RF CafeTGIF, as the saying goes. Here are a couple new vintage electronics-themed comics for your enjoyment as you wind down the work week. They appeared in a 1944 issue of Radio-Craft magazine. My favorite is the one with the lady in the vacuum cleaner repair shop. Look at her request! Her husband must have put her up to it. The other comic is pretty good, too. Having lived toward the end of the vacuum tube era, my appreciation of the equipment is more for the nostalgic quality than memories of having to wait for the tubes to warm up and re-tuning the radio and TV set at intervals while listening and/or watching...

NASA Seeks Space Relay and Navigation Services

NASA Seeks Space Relay and Navigation Services - RF Cafe"NASA has issued a formal request for information from domestic and international companies on their capabilities to provide satellite-based communication and navigation services near Earth. The effort aims to transition space mission support from government-operated systems to commercial satellite services. This call is part of the agency's broader Communications Services Project, which seeks to develop partnerships with private industry to address the needs of upcoming science and exploration missions. 'As part of NASA's Communications Services Project, the agency is working with private industry to solve challenges for future exploration,' said Kevin Coggins, deputy associate administrator of NASA's SCaN Program..."

Do You Know Your DC Circuits?

Do You Know Your DC Circuits?, May 1973 Popular Electronics - RF CafeA series of three articles appeared in 1973 issues of Popular Electronics that conducted a high-level review - or introduction if you've never seen it before - of DC circuit analysis. In this first installment, Professor Arthur Seidman, of the Pratt Institute, covers a variety of subjects starting with direct current (DC) circuit theory. Ideal current and voltage sources, units and notations, Ohm's law, Kirchhoff's law, resistors, capacitor and inductor charge and discharge curves, series and parallel circuits, power calculations, conductance, and other good stuff is covered. There is even (gasp) a bit of calculus presented...

Tunnel Diodes

Tunnel Diodes, July 1969 Electronics World - RF CafeA decade after tunnel diodes were first invented by Nobel Laureate Leo Esaki, grand plans for the unique device never played out. Predictions included its use for computer solid state memories to replace magnetic core arrays. Tunnel diodes benefitted from the aura surrounding their exploitation of the quantum mechanical tunneling phenomenon, which had a futuristic ring to it. Conventional diodes, having a relatively wide depletion region, require the current carriers (electrons and holes) to overcome a potential hill in traveling from the valence band to the conduction band of energies. Since high doping levels are used in the tunnel diode, a narrow depletion region is formed at the junction. This allows electrons...

Calvin & Phineas Hamming It Up®™: Saving Field Day

Calvin & Phineas Hamming It Up®™: Saving Field Day, by Kirt Blattenberger - RF CafeAmateur Extra-class teenagers Calvin Nolten and Phineas Thorin embark on a mission to track down the source of spurious signals in the 70 cm Ham band which threaten DX contesting on Field Day. The story is Saving Field Day, wherein, Calvin Nolten, a pint-sized shockwave of teenage pandemonium, slammed open the front door of his home with a report that could've been mistaken for a misfiring capacitor, the frame shuddering as if protesting the assault. At fifteen, barely scraping five-and-a-half feet, Calvin was a bundle of raw energy. His school backpack was a chaotic jumble of ham radio manuals, a late-model Galaxy smartphone, and lunchtime leftovers. He stormed the kitchen, raided the fridge for a quick snack, and before the light inside had a chance to go out, Calvin was out the back door, bound for Phineas Thorin's basement "shack." Mrs. Nolten, unperturbed by the familiar maelstrom, took solace in know that the chaos meant her boy was home safe - and likely already plotting some radio mischief with his partner in crime next door...

Today in Science History

Today in Science History - RF Cafe

RF Cafe Homepage Archives

The RF Cafe Homepage Archive is a comprehensive collection of every item appearing daily on this website since 2012 - and many from earlier years.

Crossword Puzzle, March 1962 Popular Electronics

Electronics Crossword Puzzle, March 1962 Popular Electronics - RF CafeBeing an old-school old guy (turn 64 this year), I still work the crossword puzzle in the daily newspaper - surely you've heard of antiquated print media form of which I am the only house on my street which has it delivered daily. I also like the cryptogram type word jumble puzzles. Working the Sudoku puzzles is also a pencil and paper exercise (as opposed to interactive online) because of my method of figuring out the numbers. My older sister is a whiz at them, and she does them on her iPhone. Old habits die hard, as the saying goes. But I digress. In addition to the weekly RF Cafe Engineering and Science crossword puzzles I create each week, I also like to post crosswords that appeared in the vintage electronics magazines. This one appeared in the March 1962 issue of Popular Electronics...

Protect Against Lightning

Protect Against Lightning, July 1955 Radio & Television News - RF CafeLightning has not changed since the days when Benjamin Franklin flew his special kite during storms. Contrary to some peoples' belief, he did not "discover electricity;" rather, the experiment proved his theory that lightning was a form of electrical discharge. Maybe someone has already pointed this out, but in effect Franklin put into service the world's first lightning rod. The conductive (wet with rain) hemp rope between the metal wire spike on the kite and ground (the plate of a Leyden jar) performed the task a lightning rod is meant to do - lower the difference of potential between the charged clouds and ground, thereby reducing the likelihood of an electrical discharge. An induced current traveled along the rope and charged the Leyden jar. If lightning had actually struck the kite as fables suggest, Franklin would probably have been killed even though he was holding on to a silk string attached to the bottom of the hemp string to provide some insulation. Mr. Kirchhoff's current law would have apportioned the lightning strike current at the knot joining the two strings according to the respective...

Red Cross Emergency Communications Test

Red Cross Emergency Communications Test, May 1941 QST - RF CafeComic strips used to be a popular venue for instruction as well as for humor. Early editions of QST and many other magazines often had many small comics scattered throughout. The one featured here came from the May 1941 QST. Amateurs were and still are a vital part of disaster response efforts. In fact it is pretty much inarguable that a big part of why the FCC has not stripped away a larger portion of the allocated Ham bands is due to the thousands of operators who volunteer their time and equipment to assist government and private agencies with communications during times of duress. Some have argued that the "amateurs" often do a much better job at disseminating time-critical information that the "professionals."

Measuring Semiconductor Device Input Parameters with Vector Analysis

Measuring Semiconductor Device Input Parameters with Vector Analysis - RF CafeJoe Cahak, owner of Sunshine Design Engineering Services in Ramona, California, has written a white paper entitled, "Measuring Semiconductor Device Input Parameters with Vector Analysis." This article covers a recent test experience that utilized some thinking about the test fixture, the bias requirements and the device mounting and special calibration offsets needed to de-embed the test fixture response from the device response within the test fixture. The device also had to have bias on several ports simultaneously. We had to establish a "reference plane" within the fixture, from which we can use the Vector Network Analyzer's Port Extension or Phase Offset to dial out the distance from our 1 port calibration reference plane to the point of short reference within the fixture. With this phase offset compensation we can then measure...

An Inside Story About Metal Tubes

An Inside Story About Metal Tubes, October 1935 Radio-Craft - RF CafeThe advent of metal-encapsulated vacuum tubes was supposed to be the death knell for traditional glass tubes. This 1935 article from Radio-Craft spelled out the many virtues of "metal" tube and how in short order their superiority would obviate the need - even desire - for "glass" tubes. I'll let you read the article for the details, but want to make note of an evidently archaic term used that could potentially be really popular in today's manufacturing world if duly resurrected - "quantiquality" (aka "quanti-quality" or "quanti quality"). The connotation is a process of high quantity in conjunction with high quality. The only references I could easily find to quantiquality was from late-19th-century newspaper archives. If sometime within the next few years you start seeing some form of quantiquality appear in marketing copy and scholarly papers, remember that you heard it here first...

Beware the Service Gyp!

Beware the Service Gyp!, September 1934 Radio-Craft - RF CafeRepair service businesses have always gotten a bad rap for deliberately inflating part and labor costs - often deservingly so - but it's a shame the honest brokers are dragged down by the scum (or "gyps" as this article calls them). Come to think of it, the word "gyp" is likely short for "gypsy," which is sure to offend someone these days. Along with admonishing customers to beware of shyster servicemen, there is an example of an orchestrated "sting" operation whereby a radio set was intentionally "broken" in a certain way with witnesses as to the fault, and then a couple dozen repair services were called upon to troubleshoot and fix it, then present a bill for their work. The result is interesting, and even resulted in one guy being prosecuted. The story reminds me of a similar much-publicized sting that was done back in the 1990s against car repair services that were creating leaks in brake lines and then charging customers to fix them...

Dipoles and Yagis

Dipoles and Yagis, November 1958 Radio-Electronics - RF CafeHere is a very useful article on the benefits and technical challenges of stacking antennas; it appeared in a 1958 issue of Radio-Electronics magazine. It avoids rigorous mathematical analysis and instead presents recommended guidelines and includes some very nice measured antenna patterns (no computer-generated predictions in 1958) of the various configurations. The authors discuss radiation pattern changes based on horizontal versus vertical stacking, and a combination of both. Plotting all the vertical and horizontal radiation patterns would have take a lot of time with a slide rule back in the day. This is the first of a series written by engineers at the Scala Radio Company...

Electronic Analogy Quiz

Electronic Analogy Quiz, November 1961 Popular Electronics - RF CafeIt is common in electronics courses for an analogy to be drawn between electrical and mechanical phenomena. In fact, a lot of circuit analysis methods and equations apply directly to mechanics, and vice versa. An LC (inductor-capacitor) oscillating tank circuit is akin to a spring and dashpot. Resistance of a wire is likened to skin friction of water flowing through a hose. Who among us can forget those lessons? This Electronic Analogy Quiz from the November 1961 edition of Popular Electronics magazine presents a challenge both because some not-so-familiar examples of analogies are offered, and because some are a real stretch. Therefore, don't feel too bad if you don't get a few. That's my way of saying that I didn't get all of them right ;-) Answers and explanations are at the bottom of the page...

Transmission Lines and Coaxial Connectors

Transmission Lines and Coaxial Connectors - RF CafeIn our continuing saga Wireless Networking in the Developing World, we now turn our attention to transmission lines and coaxial connectors, where we find: The transmitter that generates the RF power to drive the antenna is usually located at some distance from the antenna terminals. The connecting link between the two is the RF transmission line. Its purpose is to carry RF power from one place to another, and to do this as efficiently as possible. From the receiver side, the antenna is responsible for picking up any radio signals in the air and passing them to the receiver with the minimum amount of distortion and maximum efficiency, so that the radio has its best chance to decode the signal. For these reasons, the RF cable has a very important role in radio systems: it must maintain the integrity of the signals in both directions...

Questions and Answers on Oscilloscopes

Questions and Answers on Oscilloscopes, April 1957 Radio & TV News - RF CafeSimpson Electric is a name most RF Cafe visitors are probably familiar with as being the maker of high quality analog multimeters, with the Simpson 260 line being the most famous (it is still manufactured today). Not as many people, however, know that Simpson also used to make oscilloscopes. This article from a 1957 issue of Radio & TV News magazine was written by a Simpson Electric engineer whose job was, in part, to respond to questions asked by users. It covers basic operations like how to calibrate the display, adjust the horizontal time base and vertical amplitude scales, and how to synchronize the display with the input signal. Some explanation of how to interpret periodic and pulse type waveforms is provided as well as tips on how to avoid overloading and possibly damaging the instrument...

Planning Integrated Signal Communications

Planning Integrated Signal Communications, December 1950 Radio & Television News - RF CafeThe U.S. Army's Signal Corps was set up to "exercise supervision over signal communications literally from the Pentagon to the foxhole." Created in 1860 at the suggestion of a military doctor, the Signal Corps originally used a system of flag waving for messaging dubbed "wigwag" and graduated to overseeing the nationwide telegraph network six years later. By 1870, members were tasked with establishing and operating a weather forecasting service, so in 1907 when they created an aeronautical division it was just in time for facilitating the nation's rapidly growing cadre of aircraft pioneers (recall the Wright brothers had flown four years earlier at Kitty Hawk) by providing en route weather information. Having already mastered the state of the art that was radio and telephone...

Test Tube for Sound: Bell Telephone Labs

Test Tube for Sound: Bell Telephone Labs, December 1947 Radio News - RF CafeSome people like to demean engineers and scientists for their propensity to want to conduct experiments and obtain measured, empirical data rather than "winging it" and being satisfied with intuitive knowledge or the contemporarily popular term "gut." If mankind had not adopted scientific methods and ventured beyond the so-called cradle of civilization on the African continent, we would all still be living in grass huts, hurling rocks at prey, and foraging for berries. Quantifying and categorizing all things in nature helps inventors create new and improved implements that help make life better. Early on it was mostly individuals like Archimedes, Euler, Newton, and Edison who built the pool of knowledge that fed and evolved into corporations, governments, and universities doing the vast majority of the work. Bell Laboratories is probably one of the most recognizable names for a group of people that collectively produced an immense amount of data and products...

Vector-Circuit Matching Quiz

Vector-Circuit Matching Quiz, June 1970 Popular Electronics - RF CafeThis vector circuit matching quiz will hurt the brain a little more than most of the ones that were printed in Popular Electronics. In order to score well, it helps to visualize the circuits relative to where they would appear on a Smith Chart. Capacitive impedances lie in the bottom half and have negative phases (-s, -jω). Inductance lie in the upper half and have positive phases (s, jω). The familiar 'ELI the ICE man' mnemonic helps, too. Be sure to pay attention to the color of the vector arrow heads. Example: In a purely inductive circuit like #4, voltage leads current by 90°. Since phase rotation is CCW, you need to look for lettered phase diagram where the white arrowhead (voltage) is 90° ahead of the black arrow head...

Mac's Service Shop: A Typical Day in the Shop

Mac's Service Shop: A Typical Day in the Shop, July 1955 Radio & Television News - RF CafeJust as the title of this installment of Mac's Service Shop, "A Typical Day in the Shop," suggests, the story is a recollection of the kinds of scenarios that would found in an ordinary shift in an electronics service business in the mid 1950's. Vacuum tubes were the norm of the day, as were discrete leaded components and a rat's nest of wires running from solder lug to solder lug. Printed circuit boards were beginning to appear in commercial products, but mostly existed in specialty defense and aerospace applications. You might wonder how many different ways could there be for simple circuits like biasing and heater element lighting, but some pretty imaginative variations made their way into radios, television, record players, and tape decks, and often times that made a serviceman's life heck. Such was the case here as über-owner-technician Mac admonishes sidekick Barney for not taking time...

Lissajous Pattern Quiz

Lissajous Pattern Quiz, September 1963 Popular Electronics - RF CafeJules Antoine Lissajous was a French mathematician who in the days before oscilloscopes concerned himself with patterns (waveforms) that would be generated as the result of two separate functions (signals) driving both the x- and y-axes. Lissajous used mechanical vibration devices connected to mirrors to bounce light beams onto a projection surface, so his results were not merely hand-drawn plots on graph paper. He was probably as mesmerized with them as we are today when they appear. Sci-fi movies have used Lissajous patterns in the background to 'wow' the audience into thinking it is witnessing futuristic, cutting-edge technology. When troubleshooting analog circuits, it is very advantageous to have seen and recognize many different types of waveforms so that you have a better chance of picking out patterns ...

LadyBug LB5954L Power Sensor with LAN Option - RF Cafe