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KR Electronics (RF Filters) - RF Cafe
Today in Science History

The Bridged-T

"The Bridged-T Filter, February 1964 Radio-Electronics - RF CafeThe bridged-T filter is a quick-and-dirty construct used to notch out a specific frequency that is interfering with a desirable frequency or band of frequencies. It is a resonant LC (inductor-capacitor) circuit consisting of a single inductor "bridging" a pair of series capacitors having a resistor to ground between them, or, if preferred, a capacitor bridging one or two inductors. A convenient nomogram (aka nomograph) is provided by the author in this 1964 Radio-Electronics magazine article for quickly selecting values, which was a very popular design aid in the pre-calculator era. A slide rule could be used to calculate a range of values when only a single variable was in play, but juggling more than one variable (component value) was greatly aided by a multivariable nomograph. Truth is nomographs can still...

Carl & Jerry: TV Picture

Carl & Jerry: TV Picture, June 1955 Popular Electronics - RF CafeTelevision, in 1955, was still a relatively new phenomenon to many - maybe even most - people. According to multiple sources, the portion of American households with a TV set went from under 20% in 1950 to nearly 90% ten years later in 1960. That was a meteoric rise, particularly considering the expense of even a minimal TV. The technology was not even available commercially when most people were born, so the rush to join in on the craze was akin to the mass adoption of cellphones in the 1990s. "Carl & Jerry" creator John Frye used his pair of electronics-savvy teenagers to help make the "magic" behind recreating a moving picture on a CRT miles away from where it was created. Water flowing through a garden hose has often been employed as an analogy for current flowing through a wire to explain electricity to laymen and beginning students of the craft. Here, it is not water flowing through the hose but water leaving the hose and flowing through the air that serves to represent an electron stream travelling from the electron gun to the phosphor-coated glass front of a CRT. Frame rates, scan lines, deflection coils, and other relevant terms are i

RF Front-End Tech Drives Automotive Innovation

RF Front-End Tech Drives Automotive Innovation - RF Cafe"The RF front-end (RFFE) industry, valued at $21 billion, is expanding beyond its traditional focus on mobile and infrastructure to drive innovation in the automotive sector. Each segment within the industry presents unique dynamics and growth opportunities. After a difficult 2022, the smartphone market is showing signs of recovery, with expected year-over-year growth of 4%, projected to reach 1.2 billion units by 2024. The mobile RFFE market is predicted to hit US$18 billion by the end of 2024, though it may face stagnation due to market saturation and pricing pressures. This market is expected to expand, with the 2027 launch of RedCap..."

Magnetoresistance: Better Than Hall-Effect Multipliers

Magnetoresistance: Better than Hall-Effect Multipliers, April 6, 1964 Electronics Magazine - RF CafeI'm having a hard time writing this with my eyes rolled back in my head. The last time I experienced this level of overwhelmedness was probably the third or fourth week of my feedback and control class at UVM. Even though electricity and magnetism shares many complimentary and parallel concepts, for some reason thinking in terms of magnetics when describing amplifiers, mixers, modulators, etc., has always caused brain freeze. Maybe it has to do with an ingrained bias due to my earliest dealings with circuits being from a technician background before earning an engineering degree. The equations of electric fields and magnetic fields are very similar so that helps lower...

Thanks to Temwell for Their Support!

Temwell (filters) - RF CafeTemwell is a manufacturer of 5G wireless communications filters for aerospace, satellite communication, AIoT, 5G networking, IoV, drone, mining transmission, IoT, medical, military, laboratory, transportation, energy, broadcasting (CATV), and etc. An RF helical bandpass specialist since 1994, we have posted >5,000 completed spec sheets online for all kinds of RF filters including helical, cavity, LC, and SMD. Standard highpass, lowpass, bandpass, and bandstop, as well as duplexer/diplexer, multiplexer. Also RF combiners, splitters, power dividers, attenuators, circulators, couplers, PA, LNA, and obsolete coil & inductor solutions.

What's Your EQ?

What's Your EQ?, February 1962 Radio-Electronics - RF Cafe Here we are with another set of three "What's Your EQ?" circuit challenges, these from the February 1962 issue of Radio-Electronics magazine. As usual, those challenges provided by Jack Darr are the purview of television servicemen of the era. The photo shown of the problematic CRT display looks like a chest x-ray or maybe hieroglyphics in the dark corner of a cave, but evidently the artifacts are readily identifiable to an initiated few. The Forbidden Current Path circuit answer is not what I thought it would be. I maintain that whether my answer or the designer's answer is correct depends on the physical...

New Wireless Data Rate Record Set

New Wireless Data Rate Record Set - RF Cafe"A new world record in wireless transmission, promising faster and more reliable wireless communications, has been set by researchers from UCL. The team successfully sent data over the air at a speed of 938 Gb/s over a record frequency range of 5–150 GHz. This speed is up to 9,380 times faster than the best average 5G download speed in the UK, which is currently 100 Mb/s or over. The total bandwidth of 145 GHz is more than five times higher than the previous wireless transmission world record. Typically, wireless networks transmit information using radio waves over a narrow range of frequencies..."

Sputnik: A Brief History

Sputnik: A Brief History - RF CafeSputnik refers to the first series of satellites launched by the Soviet Union. The word "Sputnik" means "satellite" in Russian. The launch of Sputnik 1 on October 4, 1957, marked a monumental moment in human history, heralding the dawn of the Space Age and sparking a fierce technological competition known as the Space Race between the United States and the Soviet Union. This satellite, the world's first artificial one, orbited Earth at an altitude of roughly 215 to 939 kilometers and broadcast a radio signal that astonished the world, particularly in the United States, where it spurred rapid advancements in aerospace and scientific research. The successful launch of Sputnik was an achievement that was years in the making, involving a combination of visionary planning, political motives, and intensive engineering by some of the Soviet Union's top scientists.

Blog: Air Quality Measurements with Particle Counters

Axiom Test Equipment Blog: Provide Essential Air Quality Measurements with These Particle Counters - RF CafeTranscat | Axiom Test Equipment, an electronic test equipment rental and sales company has published a new blog post entitled "Provide Essential Air Quality Measurements with These Particle Counters" that covers how particle counters can provide essential measurement capabilities that can help avoid contamination and support high manufacturing yields. These measurement tools can detect and measure microscopic particles suspended in air that can contaminate the most carefully planned manufacturing lines. Air particle counters can be designed for various...

Receiving U.S. Satellite Signals

Receiving U.S. Satellite Signals, March 1958 Radio News - RF CafeIn 1958, most people were not accustomed to seeing the now-familiar maps plotting sinusoidal courses of satellites across the face of the earth. It had only been in October of the previous year that any object other than the moon was in orbit around our home planet - that was U.S.S.R.'s Sputnik. Just as people of all ages and all backgrounds enthusiastically joined in the newfangled phenomenon of aeroplanes after the Wright Brothers flew their fragile craft at Kitty Hawk, electronics communications and scientists worldwide hopped aboard the satellite train. This article from a 1958 issue of Radio & TV News magazine provided insight into the construction and flight characteristics...

Thanks Again to LadyBug Technologies for Continued Support!

LadyBug Technologies RF Power Sensors - RF CafeLadyBug Technologies was founded in 2004 by two microwave engineers with a passion for quality microwave test instrumentation. Our employees offer many years experience in the design and manufacture of the worlds best vector network analyzers, spectrum analyzers, power meters and associated components. The management team has additional experience in optical power testing, military radar and a variety of programming environments including LabVIEW, VEE and other languages often used in programmatic systems. Extensive experience in a broad spectrum of demanding measurement applications. You can be assured that our Power Sensors are designed, built, tested and calibrated without compromise.

Radio and Television News - Predictions

Radio and Television News, January 1969 Electronics World - RF CafeWhat were some of the top issues of the radio and television industry half a century ago? In a lot of respects, the same things that concern it today. A ready supply of service technicians was a concern that was taken seriously by the Electronics Industry Association (EIA). While there are not many local repair shops for electronics products nowadays, there is still a huge demand to techs who are willing and able to do the hard work of keeping the world's communication infrastructure operational - climbing towers, repairing cell equipment. Now, as then, good pay, job security, benefits, and respect for the job being done were at the top of...

RIGOL Introduces Oscilloscope & Generator Lines

Impressive Performance at an Impressive Price: RIGOL Introduces Oscilloscope & Generator Lines - RF CafeIn a parallel to the traditional test setup of signal generation and signal acquisition, RIGOL Technologies announced today the latest additions to its portfolio of performance measurement equipment with the introduction of the DG5000 Pro Series Generators and DHO/MHO5000 Series Oscilloscopes. The DHO/MHO5000 Series bring next-level performance to RIGOL's respected line of high-resolution oscilloscopes, while the DG5000 Pro generators do the same for the company's capable Pro Series arbitrary waveform generators...

Basic Electronic Counting

Basic Electronic Counting, March 1958 Radio News - RF CafeWhen selecting articles for posting here on RF Cafe, I like to include ones that are directed toward newcomers to the field of electronics as well as for seasoned veterans. This piece from a 1958 issue of Radio & TV News magazine entitled "Basic Electronic Counting," is a prime example in that it introduces the concept of binary numbers. We've all been there at some point in our careers. A big difference between now and when this article appeared is that in 1958, almost nobody was familiar to binary numbers, and fuggetabout [sic] octal and hexadecimal. Only those relatively few people designing and working with multimillion dollar, vacuum tube-based digital computers installed in universities, megacorporations, and government research facilities had ever dealt with digital numbers. The earliest example of powers of two I remember was back in junior high school. It had to do with a

Art of Invention Constantly Reinvented

Art of Invention Constantly Reinvented - RF cafe"Every invention begins with a problem - and the creative act of seeing a problem where others might just see unchangeable reality. For one 5-year-old, the problem was simple: She liked to have her tummy rubbed as she fell asleep. But her mom, exhausted from working two jobs, often fell asleep herself while putting her daughter to bed. 'So [the girl] invented a teddy bear that would rub her belly for her,' explains Stephanie Couch, executive director of the Lemelson MIT Program. Its mission is to nurture the next generation of inventors and entrepreneurs. Anyone can learn to be an inventor, Couch says, given the right resources and encouragement. 'Invention doesn't come from some innate genius, it's not something that only really..."

Mechanical Filters

Mechanical Filters, April 1969 Electronics World - RF CafeMechanical filters of the type described in this 1969 Electronics World magazine article are yet another example of the genius of some people. They are actually a form of electromechanical device in that the applied electrical signals are first converted into mechanical signals, followed by resonant mechanical elements that discriminate according to frequency, and finally a conversion back to an electrical signal is made. It is fundamentally the same principal as a crystal, SAW, or BAW filter, albeit each with distinctly different methods and topologies. Mr. Donovan Southworth, of Collins Radio, presents the basics of mechanical filters in this brief write-up...

Thanks Again to LadyBug Technologies for Continued Support!

LadyBug Technologies RF Power Sensors - RF CafeLadyBug Technologies was founded in 2004 by two microwave engineers with a passion for quality microwave test instrumentation. Our employees offer many years experience in the design and manufacture of the worlds best vector network analyzers, spectrum analyzers, power meters and associated components. The management team has additional experience in optical power testing, military radar and a variety of programming environments including LabVIEW, VEE and other languages often used in programmatic systems. Extensive experience in a broad spectrum of demanding measurement applications. You can be assured that our Power Sensors are designed, built, tested and calibrated without compromise.

Electronic Test Paper

Electronic Test Paper, July 1963 Radio-Electronics - RF CafeAttempts at making an electronically printed facsimile (fax) of an original document at a location distant from the source have been around for quite a while. As mentioned by Radio-Electronics magazine editor Hugo Gernsback in this article, Samuel Morse had a crude working device for printing messages on paper even before his eponymously named code of dots and dashes became famous in 1837. A couple decades earlier, a fellow named John Redman Coxe, of Philadelphia, Pennsylvania, devised a method of electronically printing images and text on paper using a conductive solution and a direct current pile (aka battery). Dr. Coxe, a physician, is not a well-known figure in the electronics world, but in his day...

"Edge of Chaos" High-Performance Microchips

"Edge of Chaos" High-Performance Microchips - RF Cafe"Researchers have discovered how the 'edge of chaos' can help electronic chips overcome signal losses, making chips simpler and more efficient. By using a metallic wire on a semi-stable material, this method allows for long metal lines to act like superconductors and amplify signals, potentially transforming chip design by eliminating the need for transistor amplifiers and reducing power usage. A stubbed toe immediately sends pain signals to the brain through several meters of axons, which are composed of highly resistive fleshy material. These axons operate using a principle known as the 'edge of chaos,' or semi-stability, enabling the swift and precise transmission of information..."

Japanese Trade-Name Directory

Japanese Trade-Name Directory, August 1969 Electronics World - RF CafeThe January 1969 issue of Electronics World magazine published an extensive list of Japanese company trade names and their addresses. Many of them went out of business or were bought by other corporations long ago, as occurs in all countries. "Aiwa" is listed twice, but that might have been a legitimate duplication due to separate locations (BTW, I owned an Aiwa stereo at one time). My first "real" cassette tape deck was made by TEAC (founded in 1953 as the Tokyo Electro Acoustic Company) and my first "real" stereo receiver was made by Sansui. I remember the line in "Back to the Future 3" where Doc Brown, having time-travelled from 1955, makes a disparaging remark about a circuit in the DeLorean failing because of it being labeled "Made in Japan." Marty counters...

Engineering & Tech Headlines <Archives>

• ARRL Defends 902-928 MHz Amateur Radio Band

• FCC's Auto Safety Spectrum Rules

• $5M in U.S. Chips Act Money to Metrology Projects

• U.S. State Department Approves Surveillance Radar System Sale to Romania

5G Americas ITU IMT-2030 Vision for 6G White Paper

John Redman Coxe: A Short Biography

John Redman Coxe: A Short Biography - RF Cafe - RF CafeJohn Redman Coxe was a prominent American physician, scientist, and innovator born on September 20, 1773, in Philadelphia. Coxe's intellect and curiosity drove him toward an illustrious career in both medicine and early scientific exploration, which included experimentation in electrochemistry. He graduated with a degree in medicine in 1794, setting the course for his lifelong journey into medicine and early scientific innovation. Coxe broadened his approach to medicine and science, inspiring him to explore the convergence of scientific methods and practical applications. John Redman Coxe is most remembered not only for his contributions to medicine but also for his interest in experimental physics, particularly in the field of electrochemistry...

Thanks to TotalTemp Technologies for Continued Support!

TotalTemp Technologies - RF CafeTotalTemp Technologies has more than 40 years of combined experience providing thermal platforms. Thermal Platforms are available to provide temperatures between -100°C and +200°C for cryogenic cooling, recirculating & circulating coolers, temperature chambers and temperature controllers, thermal range safety controllers, space simulation chambers, hybrid benchtop chambers, custom systems and platforms. Manual and automated configurations for laboratory and production environments. Please contact TotalTemp Technologies today to learn how they can help your project.

Vibration and Shock - Nature's Wrecking Crew

Vibration and Shock - Nature's Wrecking Crew, August 1966 Radio-Electronics - RF CafeWhen I saw this 1966 Radio-Electronics magazine article entitled, "Vibration and Shock - Nature's Wrecking Crew," for some reason the first thing I thought of was "The Wrecking Crew," that anonymously played the music for a huge number of popular singers - mostly those without prominent bands of their own during the 1960s and 1970s rock-and-roll era. ...but I digress. My introduction to the potential deleterious effects of vibration on electronics was in the 1970s, with airborne receivers and servos in my radio controlled model airplanes. Even though they were transistorized, vibration from glow fuel engines could wreak havoc with potentiometers in servos and solder joints everywhere, including battery packs. I remember seeing the control surfaces jitter...

Raytheon Needs Tube Design Engineers

Raytheon Manufacturing Company Needs Vacuum Tube Engineers, July 1944 QST - RF CafeYou don't see jobs advertisements like this anymore. Here is an ad that appeared in the the July 1944 edition of QST (the American Radio Relay League's, ARRL's, monthly magazine), placed by Raytheon Manufacturing Company (now just Raytheon Company), looking for vacuum tube design, test, and processing engineers. Licensed amateur radio operators were in high demand during the war years because of their knowledge and enthusiasm for electronics and wireless communications. I hope you didn't come to this page hoping to really find a tube designer job available. Of course, there are still vacuum tubes being designed for TWTs and magnetrons, but those are few and far between...

The Carborundum Signal Detector

The Carborundum Signal Detector - RF CafeThe "carborundum" signal detector, an innovative device developed by engineer General H. H. C. Dunwoody in the early 20th century, represents a significant advancement in radio technology, particularly in the context of crystal detectors used for receiving radio signals. This device utilized the unique properties of silicon carbide, also known as carborundum, which was synthesized in the late 19th century by Edward Goodrich Acheson. The connection between Dunwoody and the material lies in the application of carborundum as a semiconductor in radio signal detection. The operational theory of the carborundum signal detector is rooted in its ability to rectify alternating current (AC) signals. When radio waves, which are essentially electromagnetic waves...

Lossless Electronics with Innovative Quantum Sandwich

Lossless Electronics with Innovative Quantum Sandwich - RF Cafe"Researchers have created a cutting-edge structure by placing a very thin layer of a special insulating material between two magnetic layers. This new combination acts as a quantum anomalous Hall insulator, significantly broadening its potential use in developing ultra-efficient electronics and innovative solar technology. A Monash University-led research team has found that a structure featuring an ultra-thin topological insulator, sandwiched between two 2D ferromagnetic insulators, transforms into a large-bandgap quantum anomalous Hall insulator. This heterostructure opens the door to ultra-low energy electronics and even topological photovoltaics..."

Care and Handling of Coaxial Connectors

Care and Handling of Coaxial Connectors the Quick, Foolproof Way, August 1970 Popular Electronics - RF CafeYou have probably seen some pretty atrocious coaxial cable connector installations. You might have even been responsible for a few of them ;-(   It could be tempting, at least for frequencies in the lower megahertz range, to allow yourself to be a little sloppy with coaxial cable preparation and connector attachment, but doing so can result in marginal functionality if power levels are high or if power levels are extremely low. When voltage levels are high, excessive air gaps between the inner and outer conductors can result in arcs, and poor connections can generate intermodulation products high enough to cause interference (possibly subjecting you to a violation citation from the FCC). At very low power levels, distortions and lack of symmetry in the interface between the cable and the connector...

Bell Telephone Laboratories - Circular Waveguide Invention

Bell Telephone Laboratories, June 1955 Radio & Television News - RF CafeAccording to this full-page advertisement in the June 1955 issue of Radio & Television News magazine, Bell Telephone Laboratories was responsible for designing and fielding "waveguide pipe," aka flexible circular waveguides. According to other historical sources, both George Southworth of Bell Telephone Laboratories and Wilmer Barrow of the Massachusetts Institute of Technology (M.I.T.) independently and simultaneously developed circular waveguide, but the early devices were rigid pipe rather than being fabricated from tightly wrapped, insulated wire that permitted it to be bent rather than requiring separate corner and offset pieces. Insertion loss and VSWR is typically not as good as with rigid waveguide, but the ease of installation in many situations justifies the poorer electrical performance. Bell Telephone Laboratories was responsible ...

RF Cafe Engineering Crossword Puzzle for December 23

RF Cafe Engineering & Science Crossword Puzzle December 23, 2018Each week, for the sake of all avid cruciverbalists amongst us, I create a new technology-themed crossword puzzle using only words from my custom-created lexicon related to engineering, science, mathematics, chemistry, physics, astronomy, etc. This week's puzzle contains a special holiday message (colored clues) to all RF Cafe visitors. You will never find among the words names of politicians, mountain ranges, exotic foods or plants, movie stars, or anything of the sort. You might, however, see someone or something in the exclusion list who or that is directly related to this puzzle's theme, such as Hedy Lamarr or the Bikini Atoll, respectively...

Hughes Research and Development Laboratories

Hughes Research and Development Laboratories, October 1955 Radio & Television News - RF CafeWhen I saw this Hughes Research and Development Laboratories employment ad in a 1955 issue of Radio & Television News, I wasn't sure how to take it. The text of the ad makes no reference to the bar graph and the weird drawing. Note the "bottle" is actually a slide rule. The graph can be interpreted to indicate that the more education a person has, the less likely he is to have children. If the typical age of the respondent is in the twenties, then that might reflect how people still in school to earn a higher degree would not be having children. It might also show that people with higher degrees focus more on their careers than on having a family. If you extrapolate the graph backward, does it imply people with an Associate's degree might average 1.5 children, those with just a high school diploma have about 1.7 children, and high school dropouts average maybe 2.0 kids? You have to also assume that most of the people with higher degrees earned them prior to beginning work or else you would have to ask what the Ph.D. with 0.9 kids did...

RF & Electronics Stencils for Visio

RF & Electronics stencils for Visio r4 - RF CafeWith 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...

The Ubiquitous Ham

The Ubiquitous Ham, June 1966 Popular Electronics - RF CafeYou probably need to be a Ham radio operator to fully appreciate the humor in some of these comics. The first one, for instance, is a poke at a guy proudly pointing out his QSL cards from distant (DX) stations "right near the city limits," "on the other side of town," etc., basically what you can pull in with a home Citizens Band (CB) radio base station and a rooftop antenna. In another, the "73" signoff code is from the Western Union telegraph standard meaning "Best regards." "88" means "Love and kisses," hence the guy's unnerved response. The others don't really require an insider viewpoint. Let me know if you need any more help ;-)...

RF & Electronics Stencils for Visio

RF & Electronics stencils for Visio r4 - RF CafeWith 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...

Vintage Collins Radio Company Advertisement

Vintage Collins Radio Company Advertisement, April 1945 QST - RF CafeCollins Radio Company (later on Rockwell Collins and now Collins Aerospace) has been around since 1933. Like the vast majority of U.S. companies during the World War II era, they - management and employees - took great pride in doing their part for the war effort. Unlike today, when a relatively few people actually know someone on active duty in the armed forces, workers were very likely to have a brother, son, father, or husband in the service. Here is an advertisement that I scanned out of my copy of the April 1945 QST magazine. It mentions that many of the employees are amateur radio operators. During the war, a call went out for surplus equipment from all sources, including amateurs, so some sacrificed their personal equipment for the good...

Microwaves: Part III - Antennas and Radiators 

Microwaves: Part III - Antennas and Radiators, October 1945 Radio-Craft - RF CafeMajor Eugene Skinner (a mere Captain when the previous two parts were written) wrote many articles about radar and microwave technology for Radio-Craft magazine. In 1945 he provided a three-part series entitled "Microwaves." This third part focuses on antennas and radiators, including waveguides and feedhorns. The discussion is high level covering the basic operation of basic circuit elements, so it is excellent fodder for people new to the field - hobbyists, students, technicians, and engineers. The previous two parts are also available if you want to start at the beginning...

Sunspots Aid Radio Signals

Sunspots Aid Radio Signals, July 1957 Radio & TV News - RF CafeSunspot cycles repeat approximately every 11 years, so there had only been six solar maximums from the beginning of long distance radio communications (Marconi in 1901) up until this article was published in 1957. That year ('57) had the sun experiencing an extremely high number of sunspots (see chart below), as had the previous few years, which caused communications to be profoundly affected during the period. Under ideal conditions, high energy electrons typically ejected from the sun (coronal mass ejection, CME) cause the Earth's ionosphere to become an excellent reflector of RF energy at certain wavelengths, resulting in phenomenal long distance contacts. Under the worst conditions, extreme levels of "noise" are injected into radio signals, thereby severely degrading or even eliminating communications. This story reports on a comprehensive study on the effect of such activity on long distance communications...

Room Acoustics for Stereo and Entertainment Systems

Room Acoustics for Stereo and Entertainment Systems, February 1960 Electronics World - RF CafeHome entertainment is as big of a deal (or bigger) today as it was in the 1960's and 1970's when high fidelity personal sound gear was coming into the mainstream. Capability and features were going up while the price was coming down on really nice equipment. In order to achieve theater quality sound from your stereo and/or large screen television, thought and planning is essential or you will end up with a confusing mess of directed and reflected sounds. This article contains very valuable information on room configuration and sound absorbing materials and strategies. A fairly extensive table of common floor, wall, and ceiling sound absorption coefficients is provided, as are charts of reverberation times of various venues and volumes...

Vintage Centralab Ceramic Capacitors Ad

Centralab Ceramic Capacitors, November 1951 Radio & Television News - RF CafeCentralab (Central Radio Laboratories, aka CRL) was a major manufacturer of capacitors in the early days of radio and television, and pioneered many of the ceramic compounds that eventually replaced paper and mica as dielectrics. In fact, according to this 2-page advertisement in a 1951 issue of Radio & Television News magazine, their researchers mixed and tested more than 20,000 ceramic compounds while developing a line of capacitors that met strict precision, stability, and durability tests. It is reminiscent of Thomas Edison reportedly having tried a thousand or more filament types for his incandescent light bulb before arriving on a suitable candidate. Centralab did not invent ceramic capacitors, but they played an important role in their adoption. As with many of the early electronics companies, Centralab no longer exists. It was bought by Philips...

The Sarasota Mystery

The Sarasota Mystery, April 1966 Popular Electronics - RF CafeAfter reading both this article and "The Sarasota Mystery First Follow-Up" article in the April 1966 issue of Popular Electronics, I'm convinced that the inventor Wallace Minto either did not understand the phenomenon he describes, or he's out to punk the reader. If this initial article had been printed in the April issue rather than March, it almost certainly would have to have been a Fool's scam. Minto believes he has discovered a new form of electromagnetic propagation that exploits molecular / atomic properties of water to transmit the signal - without attenuation and without picking up noise. If it...

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...

Scatter Communication

Scatter Communication, August 1958 Radio News - RF CafeIf you are a Ham radio operator - especially a DX (long distance) operator, you have been required to study and learn about how the various layers of the Earth's ionosphere can, under predictable conditions, be an excellent reflector of certain radio wavelengths, thereby facilitating over-the-horizon communications. Reading this article is like a flashback from the license preparation manuals - particularly for the General license exam. There is a lot of information here. When this article was published in a 1958 issue of Radio & TV News magazine, the world was nearing the end of the International Geophysical Year (IGY), which had as its goal learning as much as possible about the properties of the upper atmosphere. The first earth-orbiting satellites were being launched and manned space flight was only months away, so there was much interest in learning ...

How to Target RFCafe.com for Your Google Ads

Google AdSense - it makes good sense - <em>RF Cafe</em>One aspect of advertising on the RF Cafe website I have not covered is using Google AdSense. The reason is that I never took the time to explore how - or even whether it is possible - to target a specific website for displaying your banner ads. A couple display opportunities have always been provided for Google Ads to display, but the vast majority of advertising on RF Cafe is done via private advertisers. That is, companies deal with me directly and I handle inserting their banner ads into the html page code that randomly selects and displays them. My advertising scheme is what the industry refers to as a "Tenancy Campaign," whereby a flat price per month is paid regardless of number of impressions or clicks. It is the simplest format and has seemed to work well for many companies. With nearly 4 million pageviews per year for RFCafe.com, the average impression rate per banner ad is about 225,000k per year (in eight locations on each page, with >17k pages)...

Engineering & Science Crossword Puzzle for March 15

Engineering & Science Crossword Puzzle March 15, 2020 - RF CafeThis March 15, 2020, tech-themed crossword puzzle contains only clues and terms associated with engineering, science, physical, astronomy, mathematics, chemistry, etc., which I have personally built over nearly two decades. Many new words and company names have been added that had not even been created when I started in the year 2002. You will never find a word taxing your knowledge of a numbnut soap opera star or the name of some obscure village in the Andes mountains. You might, however, encounter the name of a movie star like Hedy Lamarr or a geographical location like Tunguska, Russia, for reasons which, if you don't already know, might surprise you.

RF & Electronics Symbols for Office™

RF & Electronics Schematic & Block Diagram Symbols for Office™ r2 - RF CafeIt was a lot of work, but I finally finished a version of the "RF & Electronics Schematic & Block Diagram Symbols"" that works well with Microsoft Office™ programs Word™, Excel™, and Power Point™. This is an equivalent of the extensive set of amplifier, mixer, filter, switch, connector, waveguide, digital, analog, antenna, and other commonly used symbols for system block diagrams and schematics created for Visio™. Each of the 1,000+ symbols was exported individually from Visio in the EMF file format, then imported into Word on a Drawing Canvas. The EMF format allows an image to be scaled up or down without becoming pixelated, so all the shapes can be resized in a document and still look good. The imported symbols can also be UnGrouped into their original constituent parts for editing...

Espresso Engineering Workbook™ for Excel

RF Cafe Espresso Engineering Workbook™ for Excel - RF CafeThe newest release of RF Cafe's spreadsheet (Excel) based engineering and science calculator is now available - Espresso Engineering Workbook™. Among other additions, it now has a Butterworth Bandpass Calculator, and a Highpass Filter Calculator that does not just gain, but also phase and group delay! Since 2002, the original Calculator Workbook has been available as a free download. Continuing the tradition, RF Cafe Espresso Engineering Workbook™ is also provided at no cost, compliments of my generous sponsors. The original calculators are included, but with a vastly expanded and improved user interface. Error-trapped user input cells help prevent entry of invalid values. An extensive use of Visual Basic for Applications (VBA) functions now do most of the heavy lifting with calculations, and facilitates a wide user-selectable choice of units for voltage, frequency, speed, temperature, power, wavelength, weight, etc. In fact, a full page of units conversion calculators is included. A particularly handy feature is the ability to specify the the number of significant digits to display. Drop-down menus are provided for convenience...

Bandwidth Requirements for Pulse-Type Transmissions

Bandwidth Requirements for Pulse-Type Transmissions, February 1945 QST - RF CafeIn 1945, when this article was published in QST, radar was still in its infancy. Engineers were already aware of the need to shape pulse waveforms from experience with CW keying and the need to mitigate the effects of "chirping." A perfectly rectangular pulse in the time domain, as we learned in our signals and systems courses, creates a sin (x)/x response in the frequency domain. The Fourier transform shows that a perfectly square pulse in the time domain is the summation of an infinite number of odd harmonics of the fundamental (1st harmonic). The first few harmonics are audible to the CW copier as higher frequency "chirps." To reduce the annoyance (and wasted transmitted energy), time constants were added to the leading and trailing edges of the waveform to remove the higher frequencies, while leaving the pulse shape sufficiently rectangular to achieve its goal...

KR Electronics (RF Filters) - RF Cafe
Innovative Power Products Cool Chip Thermal Dissipation - RF Cafe

ConductRF Phased Matched RF Cables - RF Cafe

Windfreak Technologies Frequency Synthesizers - RF Cafe