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Homepage Archive #1

These archive pages are provided in order to make it easier for you to find items that you remember seeing on the RF Cafe homepage. Of course probably the easiest way to find anything on the website is to use the Google Search box in the upper left corner of every page
Homepage Archive Pages
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13
2013:  Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec

2014:  Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec


Please Welcome Triad RF Systems

Triad RF SystemsTriad RF Systems just signed on with RF Cafe as an advertiser and supporter of the website. They are a small, private company run by serial entrepreneurs, offering tower-mounted amplifiers, unmanned aerial vehicle (UAV, aka drone) amplifier systems, and many standard (30 - 6,500 MHz, up to 200 W) and custom-designed amplifier subsystems to your specifications.

Surfing at 560 M.P.H.

Surfing at 560 M.P.H, Internet on Commercial Airplanes - RF CafeHere is an interesting graphic published in the New York Times that illustrates how Internet connections in high-speed commercial aircraft manage to function reliably. I have never tried using the Internet on an airplane. Anyone care to comment?

The Future of Predictive Coding - Part II

The Future of Predictive Coding - Rise of the Evidentiary Expert? - RF CafeBut wait, there's more. IMS ExpertServices' lawyer Maggie Tamburro just published The Future of Predictive Coding (Part II) – Caveats Revealed, a continuation of her original article. At issue is whether predictive coding can be presented as an "expert" in court cases. Essentially, if I read this correctly, it would permit a computer algorithm that predicts future behavior to be admitted as evidence on par with, say, a human psychologist. The argument for predictive coding is that its criteria are selected by and code is written by humans and is therefore not a Hal (2001: A Space Odyssey) scenario. Neither is it absolutely reliable. Is it admissible for demonstrating intent to commit - or not commit - a crime? What we have is more akin to Minority Report than to 2001...

RF & Microwave Webinar

Wireless Site Survey Using a Handheld Spectrum Analyzer - RF CafeWireless Site Survey Using a Handheld Spectrum Analyzer, by Agilent Technologies, Wednesday, July 11, 1:00 pm EDT

VIP's Are Hams Too!

VIP's Are Hams Too!, March 1958 Popular Electronics - RF CafeWhat do General Curtis LeMay, Arthur Godfrey, Herbert Hoover, Arthur Collins all have in common? They were Ham radio operators. A lot of famous people were/are Hams, with these and a few other notables mentioned in this March 1958 edition of Popular Electronics. Conspicuously missing is one of modern day's most renowned Hams, and that's Walter Cronkite, KB2GSD (died in 2009). His broadcast career stretched back to World War II, so he was definitely around long enough. Maybe the author just didn't know; after all, he couldn't...

DJIA Chart Back on RF Cafe

DJIA Chart Back on RF CafeA couple years ago the DJIA market thumbnail chart I had at the bottom of the page stopped working (it is a Google Gadget), so it was removed. It is finally, it is working again, so it's back at the bottom. Now you have more reason than ever to keep returning to RF Cafe  ;-)

Hallicrafters SCR-299 Mobile Radio in WWII

Hallicrafters SCR-299 Mobile Radio in World War II - RF Cafe Video for EngineersThe definition of "mobile," at least as it pertains to battlefield communications, has changed significantly since this Hallicrafters SCR-299 radio was developed during World War II. The SCR-299 is an adaptation for battlefield use of what began life as a transmitter for amateur radio operators. Ruggedization of the entire unit was performed by factory engineers to ensure it would survive the rigors of rapid deployment over hill, over dale, as the soldiers hit the dusty trail. RF Cafe visitor Paul A. recently sent me a link to this video documentary produced by Hallicrafters showing the SCR-299 being used in the field as well as some cool factory factory production footage. Often when I am looking at an old house, or car, radio, or airplane, I envision the people who were alive at the time, putting the lathe and plaster on the walls of a home, or wrapping the paper-dielectric capacitor lead around the post used in point-to-point wiring of a radio, or maybe installing the seats in a vintage car - nameless, faceless...

Play Games with Nixie Tubes

Play Games with Nixie Tubes, March 1958 Popular Electronics - RF CafeNixie tubes were used for numeric - and sometimes alpha - displays back in the days before LEDs and LCDs. They were more light bulbs than tubes, but were encapsulated in evacuated glass shells like vacuum tubes and had round, multi-pin bases like tubes. Separate filaments were provided for each character. There were tow basic varieties: characters that displayed through the top of the tube, and characters that displayed through the side of the tube. Supposedly the name "Nixie" derived from "NIX I", an abbreviation of "Numeric Indicator eXperimental No. 1," as designated by the Burroughs Corporation sometime around...

Wireless Themed Crossword -7/8/2012

Science Theme Crossword Puzzle, July 8, 2012 - RF CafeEach week I create a new crossword puzzle that has a theme related to engineering, mathematics, chemistry, physics, and other technical words. You will never be asked the name of a movie star unless he/she was involved in a technical endeavor (e.g., Lamar)...

Homebrew Wooden Cellphone

Homebrew Wooden Cellphone - RF CafeMIT PhD candidate David Mellis has recently achieved fame for his custom designed and built cellphone. $150 worth of cobbled-together parts got him a GSM phone with an 1.8″ color , 160×128 pixel, TFT screen. He used a clever way of forming the pressable buttons in the plywood cover. Digi-Key must be happy with the unintended product placement opportunity in this picture of David and his companion trying out his wooden phone.

What Is the Higgs Boson?

Wonderful Motherboard video asks Brooklynites, "What is the Higgs Boson" - RF CafeEmployees of Wonderful Motherboard took to the streets of Brooklyn, NY, to ask people what they know about the Higgs Boson. The responses are about what you might expect. One of my sisters asked me yesterday what the Higgs Boson is. My answer was that it is basically the "equals" sign in Einstein's famous e=mc2 equation. You can quote me on that one.

Notable Quote

"Successful technology is invisible. It gets out of the way and lets us live our lives." - Amber Case - RF Cafe Notable Quote

"Successful technology is invisible. It gets out of the way and lets us live our lives." - Amber Case of Geoloqi (Jul/Aug 2012 Inc.)

Featured Book - Silicon Valley History

An Alabama Boy and the Birth of Silicon Valley - RF Cafe Featured BookAn Alabama Boy and the Birth of Silicon Valley: The Autobiography of Ernest Jerry Collins - by Ernest Jerry Collins 

"Few people would expect that someone born in the small town of Gadsden, Alabama during the Great Depression would end up being involved in everything from the US Navy to the Atlas II ICBM missile, but Ernest Jerry Collins did just that..."

Featured Book - Silicon Valley History

An Alabama Boy and the Birth of Silicon Valley - RF Cafe Featured BookAn Alabama Boy and the Birth of Silicon Valley: The Autobiography of Ernest Jerry Collins - by Ernest Jerry Collins 

"Few people would expect that someone born in the small town of Gadsden, Alabama during the Great Depression would end up being involved in everything from the US Navy to the Atlas II ICBM missile, but Ernest Jerry Collins did just that..."

The Capacitor: What It Is, What It Does...

The Capacitor: What It Is, What It Does, How It Works, April 1960 Popular Electronics - RF CafeHere is a very nice primer on capacitors that appeared in the April 1960 edition of Popular Electronics. A lot of ground is covered including history, form factors, dielectric types (ceramic mentioned as a new variety at the time), applications, etc. Interestingly, units of picofarads were still being referred to as μμfarads. In fact, since not a lot of work was being done yet in the GHz realm, there was not much use for pF other than maybe to tune a filter response. The author reveals a sense of humor when writing of early capacitance experiments as he says...

Find the Brightest Bulb

Find the Brightest Bulb, April 1960 Popular Electronics - RF CafeHere is a nifty little exercise that appeared in the April 1960 edition of Popular Electronics. It has 10 different light bulb circuits and challenges you to figure out which bulb would burn the brightest. All are intuitively obvious to most of us who have been in the field for decades, but do you remember how to do a circuit mesh analysis to prove your "gut," as the Donald would say? If you resort to building any of...

10 Minutes of Your Time, Please

Read the U.S. Declaration of Independence - RF CafeHere in America, July 4th is when we celebrate our Declaration of Independence. Please take this time to read it in its entirety. The delineated wrongs of King George III ring chillingly familiar as applicable to the government we have today: Refusal to assent to laws, forbidding his governors to pass laws of immediate and pressing importance, obstructing the laws for naturalization of foreigners. Yes, it's all in there...

Operate and Release Times of Relays

Operate and Release Times of Relays, April 1967 Electronics World - RF CafeThe April 1967 edition of Electronics World had a series of articles on designing systems with electromechanical relays. Even in today's high solid state relay world, there are still lots of applications for electromechnical relays. Only a handful of people actually design them, but the application tutorials provided therein are as valuable to today's engineers and technicians as they were 45 years ago...

Average Engineering Wages

Average Engineering Wages in the U.S. (May 2011) - RF CafeMany of the major engineering magazine websites publish annual salary survey results that have polled their readership. They always provide numbers explaining how they arrived at their charts, but in the end, those might not represent a true cross-section of salaries since they only represent people who bothered to participate. Maybe the type of person who fills out surveys tends to bias the results upward or downward. Those polls also usually include participants from other countries, with salary information being converted to U.S. dollars (although often separate charts are included showing the distribution of data by country. Still, I am never quite sure of what the numbers really mean. Since I am not sophisticated enough to collect my own statistics, instead I went to the website of the U.S. Bureau of Labor Statistics to get their latest numbers (as of May 2011) for incomes of all wage earners. Salaries used here are from the "Average...

The Future of Predictive Coding

The Future of Predictive Coding - Rise of the Evidentiary Expert? - RF CafeEvery month or so the good folks at IMS ExpertServices sends me an article written by one of their legal beagles (aka lawyers) reporting on court high tech cases that are of interest to RF Cafe visitors. They all involve use of Expert Witnesses. Here's an excerpt from this one titled The Future of Predictive Coding: "Like a dog chasing its own tail, technology has been forced to generate new solutions to deal with the escalating costs and burdens associated with legal review of massive amounts of electronically stored information..."

New Radar Shop Troop Checks In

Welcome Please welcome fellow USAF radar technician Tony Spagnolia to my honored list on the AN/MPN-14(13) ASR/PAR Mobile Radar Shop web page. If you or anyone you know is a former radar tech, please contact me and I'll be glad to add you...

Bayliss Transformers Advertisement

Bayliss Transformers Advertisement, March 9th The Wireless World Article - RF CafeThis advertisement for transformers, coils, chokes, and rotary converters from William Bayliss Ltd., on Sheepcoat Street in Birmingham, England, appeared in the March 9, 1932 edition of The Wireless World. For those not familiar with it, The Wireless World was the UK's premier electronics magazine of the day...

Free Engineering Magazine Subscriptions

Microwave Engineering Europe Subscription - RF CafeElectronic Design Subscription - RF CafeMost of the "important" technical magazines offer you a free subscriptions if you are qualified - often that means you still have a pulse. Their advertisers pay according to circulation, so higher subscription Military & Aerospace Electronics Subscription - RF CafeMicrowave Product Digest Subscription - RF Cafenumbers mean higher sales prices for them. A few of the most useful for us are Electronic Design, Microwave Engineering Europe, Military & Aerospace Electronics, and Microwave Product Digest (lots of good articles). There are a couple hundred magazines and white papers to choose from (I make about $1 on each one you subscribe to)...

Microwave Themed Crossword -7/1/2012

Science Theme Crossword Puzzle, July 1, 2012 - RF CafeEach week I create a new crossword puzzle that has a theme related to engineering, mathematics, chemistry, physics, and other technical words. You will never be asked the name of a movie star unless he/she was involved in a technical endeavor (e.g., Lamar)...

No Space Between Number and Units

No Space Between Numbers and Units - Grrrrr..... - RF CafeIn the last year, there has been a trend to forego the space between numbers and units in product datasheets and in press releases. Not only does that practice violate a centuries-old standard, but it creates an opportunity for misinterpretation. I actually asked a couple company communications people why they are doing that and they say it is to prevent units and numbers from being separated as a line wraps on the screen. I mentioned that the non-breaking space symbol (HTML &#160; or &nbsp;), aka hard space or fixed space, can be inserted...

Featured Book for Entrepreneurs

Street Smarts: An All-Purpose Tool Kit for Entrepreneurs - RF Cafe Featrued BookStreet Smarts: An All-Purpose Tool Kit for Entrepreneurs, by Norm Brodsky and Bo Burlingham. Every month I look forward to reading Norm Brodsky's sage advice to small business owners / entrepreneurs in Inc. magazine's Street Smarts column. The nut of his philosophy to crunch the numbers and make business decisions accordingly just as the big companies do. Otherwise, those who do will run right over you. OK, so now I know what to do; I just have to do it.

RF Absorbent Material (RAM) Chart

RF Absorbent Material (RAM) Chart by Emerson & Cuming - RF CafeEmerson & Cuming has a really nice chart available for determining the dielectric constant and loss tangent. It includes materials that they supply as well as for some other common materials. JP-4 fuel, various types of rubber, silica, beryllium oxide, pure water are amongst those included on the chart...

Nobel Prize "Medal Migrations"

Nobel Prize "Medal Migrations" per July 2012 Scientific American - RF CafeAccording to a survey done by Scientific American (July 2012), there has been a majority shift of Nobel Prize awards from European recipients to American recipients. The author cleverly titles the article "Medal Migrations" (metal migration - get it?). This would make me proud as an American except that I know the selection process has been greatly politicized. The graphic also includes trends in awards according to gender and age (average age increasing significantly, youngest is 25 years old, oldest is 103!). The institution with the most affiliated members...

Notable Quote

We prefer not to call people 'seats.'" -- Jason Fried - RF Cafe Notable Quote-Archive-

"In the surreal world of student loans, the brilliant student completing an electrical engineering degree at M.I.T. pays the same interest rate as the student majoring in ethnic studies at a state university who has a GPA below 2.0." - Richard Vedder, Professor of Economics, Ohio University

RF & Microwave Webinar

-Archive-

MSR Base Station Introduction and Measurement Challenges, by Agilent, Thursday, June 28, 1 pm ET

Ultra-Portable Cellular Networks for Next Generation Warfare, by Military & Aerospace Electronics, Thursday, June 28, 2:00 PM EDT

Among the Novice Hams - Nov 1957 PE

Among the Novice Hams, November 1957 Popular Electronics - RF CafeAs with on my Airplane and Rockets hobby website, a big part of my motivation for scanning and posting these vintage electronics magazine articles has been two-fold. The first reason is to provide access to historical documents for educational reasons. The second reason is to have the names of people and places published in text format (everything OCRed) so that someone doing a Web search for himself, a relative, or a friend, might run across it here...

Pop'tronics Comic Strip Electronics

Pop-tronics Comic Strip, November 1957 Popular Electronics - RF CafeThe 1950s was a time when futurists were predicting that domestic robots would be common place items in households. By the turn of the century, mankind, freed from the drudgery of manual labor, would have plenty of time for recreating, resting, and sitting around brainstorming the next big thing. Here it is 12 years into the new century and at the most, a fraction...

Crossword from 1957 Popular Electronics

Crossword Puzzle from 1957 Popular Electronics - RF CafeHere is a 1950s vintage crossword puzzle from Popular Electronics. Unlike the weekly crosswords from RF Cafe that uses only relevant technical words, this one fills in with common words. It's still a good puzzle.

CITE City: A Planned High Tech Ghost Town

Pegasus CITE City: A Planned High Tech Ghost Town - RF CafeWhen you think about a ghost town, visions might be invoked of a deserted Old West town where Wyatt Earp could have passed through, or maybe you think about a recent news story of one of the empty - or nearly so - newly constructed towns in some areas of China where a slowing economy has put big plans on hold.   Believe it or not, there is a group of investors here in America that plan to construct an entire 15 square mile city from the ground up, complete with high-rise buildings, a shopping mall, urban areas, suburbs, an airport and bus terminal, train tracks and paved roads, trees and parks, water and wastewater facilities, an electrical grid, and virtually everything else you would expect to find in a typical 20th century city with a population of around 35,000, but nobody will ever live there. People would only complicate matters by necessitating planning for and compliance with crippling regulations and accommodations. It sounds like the dream of a serious misanthrope. In reality, it is the perfect environment for conducting large scale systems testing on everything from wireless communications, to computer networking...

Life @ RF Cafe

A Perfect Summer Day in Reie, Pennsylvania, June 25, 2012 - RF CafeMore than a few people asked why we moved from North Carolina to Erie, Pennsylvania, back in 2008. This photo at least partially answers the question. The view is from the back porch of RF Cafe HQ.

Radio on Postage Stamps

Radar, Lidar, Amateur Radio, & Radio on Postage Stamps - RF CafeOver the past many decades, my involvement in stamp collecting (philately) has waned and ebbed with the amount of time available to dedicate to it. Commemorative stamps - from all countries - have always been of the greatest interest to me. Even if you are not a cruciverbalist, your interest in radio should be piqued by the large number of postage stamps that have been issued in radio's honor. Although I do not own most of the stamps pictured here, there are some that are in my collection. This is a small cross-section...

The Case of the Morse Code Oven Latch

The Case of the Morse Code Oven Latch - RF CafeIn the May 2012 edition of QST, "Hands-On Radio" column author H. Ward Silver has an article titled, "RFI Hunt." It is a very interesting saga of discovering, then troubleshooting, then correcting a very strange and unlikely issue. In a nutshell, Mr. Silver installed a new 105-foot dipole antenna about 30 feet over his house and, unbelievably, when he operated CW at 30 or 40 meters (at 25 W or higher), the door safety latch on his self-cleaning oven would energize during the dot or dash transmission. He works his way through many iterations of line chokes, bypass capacitors...

Radio Tech Positions @ U.S. Capitol Police

Radio Tech Positions @ United States Capitol Police - RF Cafe Employment ForumInstalls/maintains a wide range of radio equipment and system components, including VHF repeaters (conventional and trunked), combiners, duplexers, filters, power amplifiers, UPS, and antennas. Sets up and installs ad hoc radio networks (repeaters, receivers, duplexers, base stations, and connectivity) at off site locations in support of USCP travel missions...

Science Themed Crossword - 6/24/2012

Science Theme Crossword Puzzle, June 24, 2012 - RF CafeEach week I create a new crossword puzzle that has a theme related to engineering, mathematics, chemistry, physics, and other technical words. You will never be asked the name of a movie star unless he/she was involved in a technical endeavor (e.g., Lamar)...

Angel Flight Video

"Angel Flight" Video, Radney Foster - RF CafeAngel Flight" is the unofficial designation given to aircraft transporting fallen military members back to the USA for burial. Country songwriter/singer Radney Foster came up with a piece by that title. The video presented here is not the one posted on his site as the "official" version; this one is a remix that has the words superimposed (and there is no advertisement in it - yet). We're fast approaching...

Dave Coverly Tech Comics

"That's right dear, our ancestors had tails." Dave Coverly Comic - RF Cafe"That's how we figure out which hampster is the male," by Dave Coverly - RF CafeDave Coverly (SpeedBump.com) is an artist who frequently does tech-themed comics for newspapers on topics like cell phones, Listen, Ed, either you stop bringing your dog to work, or you name her something besides "Eureka," by Dave Coverly - RF Cafe math, "If you can read this, I need more coffee," by Dave Coverly - RF Cafescience, electronics, etc. Here are a few that I think are particularly clever.


Tech Blunder in "Air Force One" Movie

Technical Blunder in "Air Force One" Harrison Ford - RF CafeMelanie and I were watching Air Force One (Harrison Ford) the other night and there was a scene where the Prez was in the bowels of the 747 and had to jerry-rig some wiring to dump fuel. He used a butter knife to easily strip the insulation off the wires. I know from having built MIL-SPEC and aerospace harnesses that only Teflon...

Notable Quote

We prefer not to call people 'seats.'" -- Jason Fried - RF Cafe Notable Quote-Archive-

We prefer not to call people 'seats.'" -- Jason Fried, re enterprise software applications


Featured Book

Load-Pull Techniques with Applications to Power Amplifier DesignLoad-Pull Techniques with Applications to Power Amplifier Design,
by Fadhel Ghannouchi, Mohammad Hashmi


Beware Yontoo Virus

Yesterday evening, Melanie alerted me that on her computer an ad for a search company called Contenko was appearing on her web pages where Google Ads and other 300x250-pixel image ads would normally appear. She wondered if the problem was with something gone awry on RF Cafe, because that's where she first noticed it. I immediately suspected a virus and confirmed something was up after verifying that the page source code was presenting the proper images. A quick search revealed that a piece of software by Yontoo is being distributed with some downloadable software that is capable of hijacking image space and displaying its own content. It is not officially a virus, but in my book it certainly is a virus. It, without permission, usurps real estate on any web page and attempts to steal potential profit. In my case, I have RF component companies that pay to rent public space on RF Cafe web pages so if some piece of shite company decides to display their products there instead, it denies my advertisers a chance to get business. This phenomenon is not unique to RF Cafe; it does its dirty deed on any website. I suspect the software installed with a program that Melanie downloaded for her violin and cello playing since the date in the Windows Control Panel's Add/Remove area coincides (might want to check your). These things always make me reflect longingly on the story of a major hacker in Russia discovered with a ball peen hammer buried in his head.

Senior Engineer @ Millimeter Wave Products

Senior Engineer Needed by Millimeter Wave Products - RF Cafe Employment ForumFamiliar with microwave and millimeter wave amplifier designs, filters, down converters, multipliers, passive components, waveguide theory and antenna design and testing...
6/20/2012

After Class: The Particle Accelerators

After Class: Special Information on Radio, TV, Radar and Nucleonics, November 1957 Popular Electronics - RF CafeBy 1957, betatrons, cyclotrons, cosmotrons, synchrocyclotron, bevatrons, and other forms of "trons" had the physics world all agog with anticipation of the next big discovery. Quarks were still a decade away from being discovered and something as exotic of the Higgs boson (aka god particle) hadn't entered anyone's mind. The news media was agog with reports of the world...

Arbitrage via Microwaves

Arbitrage via Microwaves, McKay Brothers photo of microwave link - RF CafeIf you have wondered why the world's stock markets behave the way they do, why the DJIA falls 150 points on one day on news of Greece leaving the euro, then gaining 200 points the next day on news of a bailout, then back down a day later on more news of the bailout, your confusion is understandable. It seems that there might be nobody who actually can predict the market's contortions and that every trade is a gamble. You would be wrong. There is evidently a small group of elite, well-financed, well-equipped market players who have decision advantages measured in microseconds - just enough time to have a glimpse of the world that almost no one else has and then execute trades based on that privileged information. It allows them to test theories of market reactions and make nearly instantaneous adjustments to either increase profit on good decisions or minimize losses on bad decisions. This is referred to as "high frequency trading." Actually, software makes all the decisions, not actual humans, but of course that software is created based on human knowledge.   According to one of many articles in the June 2012 edition of IEEE's Spectrum magazine reporting on the world's money machine, a multimillion dollar microwave link has just been built between the New York Stock Exchange (NYSE) and the home of Chicago-based futures traders by the company McKay Brothers (nobody named McKay has ever worked there). Its purpose is to exploit the lack of signal delay inherent...

QA Manager @ TRM Microwave

QA Manager Needed by TRM Microwave - RF Cafe JobsTRM Microwave is looking for a Quality Assurance Manager to ensure that the product or service we provide is fit for its purpose and meets customer expectations. The QA manager coordinates the activities and develops procedures and processes required to meet this aim...

Dilbert™ on Trade Shows

Dilbert on Trade Shows - RF CafeBeing that the world's largest RF and microwave trade show, IMS2012 (aka MTT-S) is happening this week in Montreal, Canada, I thought this Dilbert™ comic strip from last month would be a fitting subject for posting on RF Cafe. Having been to a couple of the IMS shows and talking to exhibitors, many seem to actually relate to Dilbert's experience. The main value of having a presence there is often simply being seen in the realm of major players, which confers a certain level of industry prominence. So, even if spending a week at the show does not directly result in new customers, at lease some companies believe the cumulative effect of a persistent presence will pay off in the long run. I tend to agree. That being said, it looks like Melanie and I will probably not be adding to RF Cafe's cumulative advantage this year because we likely will not be going to the IMS2012 show after all. Maybe next year.

Eavesdropping on Satellites

Eavesdropping on Satellites, February 1963 Popular Electronics - Telescope & Sky1963 was five years since America's first communications satellite, Echo, was placed in orbit. Echo was a passive, spherical reflector that merely provided a good reflective surface for bouncing radio signals off of. By 1963, the space race was well underway and active communications satellites were being launched at a rapid pace. Spotting and tracking satellites has long been a popular pastime with two types of hobbyists: amateur astronomers using telescopes and binoculars, and amateur radio operators using antennas and receivers...

Metamaterials for RF

Microwave Rotman Lens by John Hunt (COMSOL article) - RF Cafe Cool PicMetamaterials are receiving as much attention in university research departments these days as graphene and carbon nanotubes. What makes metamaterials so desirable is its negative refractive index. It causes waves - be they electromagnetic or mechanical - to bend (refract) in the opposite direction as nearly every material found in nature. If water droplets had a negative index of refraction, rainbows would display color in the opposite direction with red on the bottom and violet on the top. If a negative refractive index was the norm in nature, our resistor color code would probably be reversed: 0=black, 1=brown, 2=violet, 3=blue=4, etc. So, why is a negative refractive index a big deal? It allows waves (signals) to be bent (focused) across wider bandwidths without dispersing (spreading out) the beam spatially. It can also be used to steer waves around an object in a manner that renders the object invisible within the bandwidth of interest, a prime requirement for cloaking. While cloaking is most often thought of as a military application for hiding soldiers and equipment, it is also being studied for uses such as directing earthquake waves and wind around buildings and bridge abutments...

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