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Today in Science History

Antenna Principles: Directive Arrays w/Metal-Screen Reflectors

Antenna Principles: Directive Arrays with Metal-Screen Reflectors, May 1947 Radio-Craft - RF CafePart VI of the multi-month series of articles on antenna principles which appeared in Radio-Craft magazine covers directive arrays with metal-screen reflectors. Metal-screen, wire, and mesh reflectors are discussed as reflector surfaces for broadside array, the collinear array, and billboard array collections of dipole elements. An interesting statement by author Jordan McQuay is, "It is more practical and efficient to use a reflector screen [as opposed to reflector dipole elements], particularly if there are a large number of dipoles. Such a non-resonant reflector is easier arid cheaper to construct, and provides a better broad-band response than a resonant reflector." I don't know enough about antenna deign to determine whether with modern methods of simulation and construction, if that still holds...

Engineering White Papers & Books, April 2020

Engineering White Papers & Books, April 2020 - RF CafeReading trade journals is always given as one of the main ways cited by engineers on career surveys for continuing education. Engineering whitepapers, pamphlets, books, magazines, and chapter examples listed here are a small sample of a lot of new items that are offered for FREE through TradePub. The publishers make them available to qualifying people as a promotional campaign for their full line of offerings. Whitepaper topics include careers, manufacturing, and engineering, while magazine titles include Microwave Engineering Europe, Electronic Design, and Microwave Product Digest. Note: I earn a few pennies (literally) when you download one of these or the many other pubs available, so please help yourself.

Top 20 Engineering Schools by Salary

Top 20 Engineering Schools by Salary - RF CafeThe Design News website published their list of engineering schools with alumni that earn the highest salaries. As usual, all the familiar names appear, but with some shuffling of positions. For a reason I still do not understand - and I'm not knocking it - Harvey Mudd College leads the pack with an entry level salary of $90,700 and a mid-career salary and $161,800. Stanford was #2 and MIT #3. For reasons I do understand, military academies consistently rank highly (USNA #4, USMMA #10, USCGA #19). Says, the article: "As part of Engineering Week, we're presenting the 2020 report from PayScale (2019 report) shows which schools are turning out the highest paid grads with a bachelor's or graduate degree. Two years ago we posted the results of PayScale's study that only included grads with bachelor’s degrees. The difference in the lists is surprising. PayScale defines engineering schools as those public or private institutions that grant more than 50 percent of their undergraduate degrees in math, sciences, computer science, engineering, or engineering technology majors..."

After Class - Using Load Lines

After Class - Using Load Lines, January 1956 Popular Electronics - RF CafeUse of a load line chart is a fast way of selecting the bias (operating) point and operational range for nonlinear devices. Notice that I didn't specifically say for transistors because this particular article deals with load lines for vacuum tubes. Almost nobody has any need for tube load line charts anymore, but the skill needed to interpret load lines for transistors is fundamentally the same as for tubes. Substitute Vce (collector-to-emitter voltage) for Plate Volts and Ic (collector current) for Plate Milliamperes and you have equivalence. Popular Electronics magazine ran this "After Class" tutorial series covering a broad variety of topics for many years. There is a short quiz at the end...

Spin Capacitor Cuts Heat and Power

Spin Capacitor Cuts Heat and Power - RF CafeAnd now, the cousin of the Flux Capacitor --- the Spin Capacitor! "In what is claimed to be a world first, physicists have developed a so-called spin capacitor that could herald new electronics that require less power and generate less heat. The advance by scientists at Leeds University generates and holds the spin state of electrons for a number of hours compared to previous efforts that held the spin state for a fraction of a second. Their results are published in Science Advances. A conventional capacitor holds energy in the form of electric charge and the development from Leeds does this also whilst storing the spin state of a group of electrons. According to the university, this could lead to a storage device measuring one square inch that could store 100 terabytes of data..."

Coronavirus Patent - Who Knew?

Coronavirus Patent, Who Knew? - RF CafeLet me start by saying this is NOT the COVID-19 form of coronavirus. It is patent US10130701B2 issued to a UK research entity. A CNIPA (China National Intelligence Property Administration) website search does not show any coronavirus patents - maybe the Wuhan Institute of Virology application is still pending. A search on the USPTO website for "coronavirus" (ttl) turns up 75 results. I'm not sure which makes me more uncomfortable - a communist country's patent office that shows no coronavirus patents or a representative republic country's patent office that shows scores of them, with 5 having China (cn) as the assignee country (acn).

MPDevice: RF & Microwave Circulators & Isolators

MPDevice - RF CafeMPDevice (MPD) has become a trustworthy and reliable company in the global RF market as a manufacturer of passive RF Devices. Included are attenuators and terminations, coaxial connectors, adapters, and cable assemblies, DC blocks, surge arrestors, power combiner / dividers, and directional couplers. The Korean Telecommunication market is now entering into the era of hyperconnected society. With continuous enhancement in R&D capabilities and quality control, MPD will continue in an effort to become the No. 1 technologically innovative company with a focus on the emerging 5G marketplace.

400 Million U.S. Radios?

400 Million U.S. Radios?, May 1947 Radio-Craft - RF CafeFamous quotation books are full of statements made by people - many of them "experts" - throughout history which have proven to be hilariously wrong, and unfortunately some have been tragically wrong. Thomas Watson, president of IBM, in 1943 famously predicted on digital computers, "I think there is a world market for maybe five computers." In 1946, 20th Century Fox's Darryl Zanuck declared, "Television won't be able to hold on to any market it captures after the first six months. People will soon get tired of staring at a plywood box every night." Virtually on the eve of the PC revolution (1977), DEC founder Ken Olsen, "There is no reason anyone would want a computer in their home." British Prime Minister Neville Chamberlain assured his countrymen regarding Adolph Hitler's assurance of nonaggression, "I have returned from Germany with peace for our time". In 1947 when Radio-Craft magazine founder and editor wrote this article telling of the many in-the-know types who were predicting a grave future for commercial broadcast radio once television became a common fixture in households...

Promote Your Company on RF Cafe for as Little as $40/mo.

Sponsor RF Cafe for as Little as $40 per Month - RF CafeRF Cafe typically receives 8,000-15,000 website visits each weekday and about half that on weekends. RF Cafe is a favorite of engineers, technicians, hobbyists, and students all over the world. With more than 13,000 pages in the Google search index, RF Cafe returns in favorable positions on many types of key searches, both for text and images. 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. I also re-broadcast homepage items on LinkedIn. If you need your company news to be seen, RF Cafe is the place to be. Advertising begins at $40/month.

Low-Loss Coaxial Cable

Low-Loss Coaxial Cable, December 1966 QST - RFCafeWhen it comes to low loss transmission media, it's hard to beat waveguide and open wire. Open wire can exhibit less a couple tenths of a decibel per hundred feet at low frequencies, but it is very susceptible to perturbations from nearby objects, wind and moisture. Waveguide exhibits a few tenths of a decibel per 100 feet at very high frequencies, but it is expensive and difficult to work with. In the middle is coaxial cable, which for a good quality product of appropriate size, you can get very low attenuation. As with most things, you get what you pay for in coax cable. I once used really expensive Andrew (now Commscope) Heliax coax cable on an S-band radar (2.8 GHz) system that had only a little more than 1 dB/100 ft, which was necessary from a receiver noise figure requirement rather than for transmitter power efficiency. This article from QST covers some of the basics of low loss cable...

ICNIRP Publishes New RF Electromagnetic Exposure Guidelines up to 300 GHz

ICNIRP Publishes New RF Electromagnetic Exposure Guidelines up to 300 GHz - RF Cafe"The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has released new guidelines for the protection of humans exposed to radio frequency electromagnetic fields. The guidelines cover the upcoming 5G technologies, as well as AM and DAB radio, WiFi, Bluetooth, and the currently used 3G/4G mobile phones. ICNIRP Chairman, Dr. Eric van Rongen, said the new electromagnetic field guidelines have taken seven years to develop and are more appropriate than the 1998 guidelines for the higher frequencies that will be used for 5G in the future. He added that they know parts of the community are concerned about the safety of 5G and they hope the updated guidelines will help put people at ease. The guidelines have been developed after a thorough review of all relevant scientific literature, scientific workshops..."

Make Sense of Antenna Design and Matching Networks

Make Sense of Antenna Design and Matching Networks - RF CafeMr. Asem Elshimi has an article entitled "Make Sense of Antenna Design and Matching Networks" on the EDN website. He introduces the basics of EM radiation and ideal antenna formats, then discusses acceptable compromises based on the application. "When it comes to actual antennas in the real world, much of our knowledge is empirical. We know very broadly theories that explain how a point charge radiates (Maxwell’s equations), the need for matching (microwave theory), and how dipole antennas drawn on paper radiate the way they do, but these laws are nearly useless in solving the real-world problem of antenna design. By sharing my intuition on how wireless electronics work on a physical level, I hope to be useful in shaping a broad understanding of antenna design and matching networks and underscore the value of best practices and hard-earned wisdom..." (note Fig. 1 antenna drawings appear to be mine)

Broadband Engineers Threatened over 5G Coronavirus Conspiracies

Broadband Engineers Threatened over 5G Coronavirus Conspiracies - RF Cafe"EE suspects telephone mast engulfed by fire in Birmingham was an arson attack as celebrities claim Covid-19 caused by new network ('ØG' video). Ofcom has warned broadcasters to refrain from spreading rumors that 5G is linked to coronavirus. Telecoms engineers are facing verbal and physical threats during the lockdown, as baseless conspiracy theories linking coronavirus to the rollout of 5G technology spread by celebrities such as Amanda Holden prompt members of the public to abuse those maintaining vital mobile phone and broadband networks. Facebook has removed one anti-5G group in which users were being encouraged to supply footage of them destroying mobile phone equipment, with some contributors..."

Exodus Advanced Communications: RF & Microwave Power Amplifiers

Exodus Advanced Communications - RF CafeExodus Advanced Communications is a multinational RF communication equipment and engineering service company serving both commercial and government entities and their affiliates worldwide. Power amplifiers ranging from 10 kHz to 51 GHz with various output power levels and noise figure ranges, we fully support custom designs and manufacturing requirements for both small and large volume levels. decades of combined experience in the RF field for numerous applications including military jamming, communications, radar, EMI/EMC and various commercial projects with all designing and manufacturing of our HPA, MPA, and LNA products in-house.

Radio Data Sheet 345 Admiral Model 6RT44-7B1

Radio Data Sheet 345 Admiral Model 6RT44-7B1, April 1947 Radio-Craft - RF CafeWhenever I post any of these Radio Data Sheets from vintage electronics magazines, I attempt to find photos of actual units. Drawings are good, but actually seeing a for-real example is the best option. This Admiral Model 6RT44-7B1 phonograph appears on the Radio Attic's Archive website. As mentioned previously, electronics service shops relied heavily on these Radio Data Sheets that were printed in monthly magazines like Radio-Craft, Radio News, and Radio & Television News. The alternative was purchasing service documentation from the manufacturer (often only available to factory-authorized shops), from Sam's Photofacts, or some other third-party supplier. Of course experience and intuitiveness could substitute for documentation, but as many episodes of John T. Frye's series of "Mac's Radio Service Shop" illustrates, quirky variations in circuits...

Graphene Transistor Amplifier for THz & Light

Graphene Transistor Amplifier for THz & Light - RF Cafe"A new type of graphene amplifier could offer researchers a unique way to access the electromagnetic spectrum. Engineers from Loughborough University have designed an optical transistor out of graphene and a high-temperature superconductor that can amplify terahertz frequencies, and could unlock a whole new field of potential technologies. Terahertz waves (THz) have long fascinated scientists, but unfortunately, their use has been limited by their weak signals. Without an added boost of power, the wavelengths have been too weak for researchers to harness their potential power - until now, that is. The amplifier is deceptively simple, made up of two layers of graphene and the superconductor..."

Probability Stick Broken into 3 Pieces Can Form a Triangle?

Probability Stick Broken into 3 Pieces Can Form a Triangle? - RF Cafe"There's a tricky question asked at Google and Amazon interviews that is bound to stump you. However, worry not as YouTuber Zach Star is here with the solution in this fun video. The question goes like this: let's say you have a stick that you will randomly cut in three pieces. What are the odds that the three pieces created can form a triangle? If the three pieces are about equal in size, you can make a triangle. If, however, you have two much smaller pieces, you can not. It should also be known that for a triangle to be made, the two shortest lengths combined need to be bigger than the third. How does that relate to our question? Well, you have to watch the video for that..."

Z-Comm SMV0912B-LF 865 to 960 MHz VCO

Z-Comm SMV0912B-LF Features Low Phase Noise with Extremely Low Power Consumption - RF CafeZ-Communications, Inc., announces a new RoHS compliant VCO (Voltage-Controlled Oscillator) model SMV0912B-LF. The SMV0912B-LF operates from 865 to 960 MHz within a tuning voltage range of 0 to 2.5 Vdc. This low cost VCO features very clean spectral purity performance of -100 dBc/Hz @10 kHz offset and covers the frequency range with an average sensitivity of 80 MHz/V. The SMV0912B-LF is designed to deliver 3±3 dBm of output power into a 50 ohms load while operating over the industrial temperature range of -40 to 85°C. This high performance VCO is further enhanced by saving precious energy. It consumes a mere 6 mA of current while operating off a 3.0 Vdc supply. The SMV0912B-LF features a typical 2nd harmonic suppression of -10 dBc...

Science & Math Ignorance in the Media

Coronavirus World Map (MSN) - RF CafeQuestion: According to the legend on this graphic, how many confirmed cases of coronavirus do the gray-colored areas have (answer below)? Look at this "Countries with Confirmed Cases of Coronavirus" map used in an MSN.com news story. According to graphic creator Tara, it was provided by the World Health Organization. This is an example of why the news media should not be unquestioningly believed when presenting data. Its reporters are for the most part very scientifically and mathematically ignorant (and some are plain stupid). They do not know how to assimilate and present numerical information, while pompously demanding that everyone listen to the scientists. Answer: Exactly 100. Do you understand why?

Windfreak Technologies MPDevice microwave devices - RF Cafe
Windfreak Technologies
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    Kirt Blattenberger,

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

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