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About RF Cafe

Kirt Blattenberger - RF Cafe Webmaster

Copyright: 1996 - 2024


    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 World Wide Web (Internet) was largely an unknown entity at the time and bandwidth was a scarce commodity. Dial-up modems blazed along at 14.4 kbps while typing up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

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Tech Topics Smorgasbord Archives - 36

RF Cafe University"Factoids," "Kirt's Cogitations," and "Tech Topics Smorgasbord" are all manifestations of my rantings on various subjects relevant (usually) to the overall RF Cafe theme. All may be accessed on these pages:

 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36

Electronics Themed ASCII Art

Electronics Themed ASCII Art - RF Cafe SmorgasbordASCII Art has been around nearly as long as digital computers have been in existence. It was the only type of "graphics" available to most users before other than text displays were commonplace. Universities, corporations, and government research facilities had crude forms of graphical displays, but it was not until the 16-color, 640x200-pixel CGA (Color Graphics Adapter) monitors began shipping with IBM PCs that most people had access to "real" graphics. To compensate, some pretty clever souls came up with what has become known as "ASCII Art." ASCII (American Standard Code for Information Interchange), for those of you too young to remember when that was part of common computer parlance, is the basic set of numbers, letters, and special characters that all computers are capable of rendering based on unique codes assigned to them. For instance, ASCII character 48D (30H) is the number "0," 65D (41H) is upper case "A,"...

Log Polar Plane Stencil c1958

Log Polar Plane Stencil c1958 - RF Cafe SmorgasbordCanadian website visitor Richard F. sent me this photo of his "Log Polar Plane" acetate stencil, circa 1958. As a collector of vintage of science / technical paraphernalia, he ran across this as part of one of his acquisitions. "Computing Aids" is printed on it. I had never heard of the log polar plane, but according to the Wikipedia entry, "In mathematics, log-polar coordinates (or logarithmic polar coordinates) is a coordinate system in two dimensions, where a point is identified by two numbers, one for the logarithm of the distance to a certain point, and one for an angle. Log-polar coordinates are closely connected to polar coordinates, which are usually used to describe domains in the plane with some sort of rotational symmetry. In areas like harmonic and complex analysis, the log-polar coordinates are more canonical than polar coordinates." The David Young, on the University of Edinburgh website, explains, "Log-polar sampling is a spatially-variant image representation..."

Engineering and Technology History Wiki (ETHW) - Dr. Dave Leeson

Engineering and Technology History Wiki (ETHW), Dr. Dave Leeson - RF Cafe SmorgasbordIf you have not yet discovered the Engineering and Technology History Wiki (ETHW) website, now would be a good time to surf on over and take a look at the vast resources there - particularly the "Oral-History" series of in-person interviews of our field's top scientists and engineers. Among them are Dr. Harold Beverage, Dr. Ulrich L. Rohde (N1UL), Harold S. Black, Harold A. Wheeler, Dr. Irwin Jacobs and Dr. Andrew Viterbi, and of particular significance to me, Dr. David B. Leeson (W6NL), founder of California Microwave and Ham radio contesting champion. Many of the oral interviews were conducted in the pre-Internet era and some of the people are no longer with us. A few days ago, I had the honor of being contacted Dr. Leeson as part of his search for information he wants for some work he is doing. His name is familiar to amateur radio contesters who participate in DX (long distance) events...

What Does My Overheated Transmissions Have to Do with Admiral Grace Hopper?

What Does My Overheated Transmissions Have to Do with Admiral Grace Hopper?r, Kirt's Cogitations #330 - RF CafeLast week Melanie and I drove down to Greensboro, North Carolina, to attend our daughter's wedding. The weather was typically hot there, but not out of the norm. All went well at the small ceremony. Both bride and groom showed up, as did the minister and necessary witnesses. After the blessed event was over, we headed back northward to our humble abode in Erie, Pennsylvania. Our route upon exiting NC is I81 for a few miles in Virginia, then north onto I77, up to Rt. 19, then I79 all the way home up and down mountains for a few hundred miles. Our 2011 Jeep Patriot has never had any mechanical issues, but then it only has 81k miles on it and is kept in the garage. That day, though, the transmission overheating idiot light illuminated while on I81 - not a particularly hilly stretch. The outside temperature there was about 80 °F. I had noticed a slightly higher pitch sound from it while going uphill, but didn't think anything of it until the light came on. (On−Trak Automotive Services)...

COVID-19 Vaccination Effort Has No Statistically Significant Control Group

COVID-19 Vaccination Effort Has No Statistically Significant Control Group, Kirt's Cogitations #329 - RF CafeLet me begin by stating that in general, I am not an "anti-vaxxer." Since my days in the USAF, I have chosen to get an annual flu shot, my kids received all the required / recommended vaccinations during their school years. I've even had the second-generation shingles shots. No problemo. All those vaccines were subject to the full scientific regimen of development and testing prior to being administered to the general public. The current crop of COVID−19 vaccines, however, are a major exception - especially the mRNA varieties. None have been thoroughly vetted with the traditional multi-year studies which include a very wide cross-section of voluntary participants. Furthermore, none have been approved by normal guidelines - these are emergency approvals. Statistical studies were performed which attempted to correlate cause and effect. If necessary, necessary modifications to the formulation were made and then trials began anew. Once the medical and science community had enough data...

PS Magazine: The Preventative Maintenance Monthly

PS Magazine: The Preventative Maintenance Monthly, Kirt's Cogitations #328 - RF CafeA few times in the past I have mentioned the U.S. Army's long-running comic-book-style of training material for vehicle maintenance. It began in 1940 under the title of The Army Motors and ran through the end of World War II. In June 1951, at the beginning of the Korean War, the publication was re-introduced as PS Magazine - The Preventative Maintenance Monthly, where the "PS" part stands for "Post Script," a la the "p.s." you might put at the end of a written letter. In this case the "p.s." is a post script to the regular Army vehicle maintenance manuals. I recently happened to run across the RadioNerds.com's extensive section on PS Magazine, and it is a treasure trove of downloadable PDF versions of the magazines. As you can see from the cover illustrations and the contents, its appeal was primarily to the predominantly male vehicle maintenance force...

How Long Is 1 Trillion Seconds?

How Long Is 1 Trillion Secsonds? Kirt's Cogitations #327 - RF CafeEngineers are entirely comfortable with numbers multiplied by very large powers of 10; that is, with many trailing (or leading if a decimal) zeros after the significant figures. A terahertz is 1 x 1012, or 1 followed by twelve zeros, or 1,000,000,000,000. A picosecond is 1 x 10-12, or eleven zeros between the decimal point and the one, or 0.000000000001. The mass of the sun is approximately 1.9885×1030 kg, or 1,988,500,000,000,000,000,000,000,000,000 kg. The mass of an electron is approximately 9.10938×10−31 kg, or 0.000000000000000000000000000000910938 kg. We don't even break a sweat when punching those kinds of numbers into a calculator. We're used to it. When most laypeople these days hear politicians nonchalantly toss around figures in the trillions of dollars regarding a country's deficit or planned new spending packages, or the net worth of Amazon's Jeff Bezos, Tesla's Elon Musk, and Donald Trump, they have no concept of how big the numbers are...

1940 Sears Amateur Radio & Test Equipment Catalog

1940 Amateur Radio & Test Equipment Catalog Sears Catalog Kirt's Cogitations #326 - RF CafeRF Cave visitor and contributor Joseph Birsa (N3TTE), sent me a note about yet another edition of a special purpose catalog published by Sears - the Sears 1940 Amateur Radio, Test Equipment, Sound System Catalog. A little research revealed that it was actually an extended version of the 1940 Sears, Roebuck and Co. Superior Amateur Equipment and Radio Service Supplies - 64 versus 48 pages, respectively. Even the standard edition Sears, Roebuck Fall 1941 Catalog contained a large section dedicated to radios and equipment. The cover on the shorter catalog makes me think of The Radio Boys series of books, where a cadre of four early 20th century teenagers experienced adventures centered around build and operating wireless equipment. Hallicrafters, National Company, Meissner, and Hammarlund receivers and transmitters were offered for sale. Bliley and Silvertone...

Inventors and Their Inventions - #325

Inventors and Their Inventions, Kirt's Cogitations #325 - RF CafeWhen doing some research for creating a new quiz on inventors and their inventions, I decided to look for people according to their countries. I almost always do image searches since doing so does a good job of filtering out pages that merely mention the topic of interest. My first Google search was "american inventors." I expected to see the familiar faces of Thomas Edison, Henry Ford, George Westinghouse, Marie Curie, Alexander Graham Bell, George Washington Carver, Edwin Armstrong, Hedy Lamarr, Benjamin Franklin, Robert Goddard, Albert Einstein, the Wright Brothers, Samuel Morse, William Shockley, etc. Those are the names that first come to my mind, and admittedly the list is dominated by White men. Imagine my surprise when the Google search results belied my perception. Take a look at the first few pages of results to see what I mean. Next, I moved on to an image search for "canadian inventors..."

QST Christmas Covers - #324

QST Christmas Covers, Kirt's Cogitations #324 - RF CafeAs our traditions are besieged by malcontents determined to denigrate, impugn, and ultimately erase memories of holidays and events that have meant so much to families and friends, I feel compelled to resist the movement by documenting parts of the past that will cause us to wax nostalgic over our cherished traditions. Intimidation and violence is part of the strategic calculus; we have seen it in spades in 2020, and 2021 promises to be even worse. The Cancel Culture might eventually win out with the complicity of government agents both elected and unelected, but I'm not going down without a fight. Here is a collection of twentieth century, December issue QST magazine covers with Christmas themes that will no doubt be familiar to many of you. Finding them was more difficult...

December 24, 2020

Engineering Documentation Methods Questionnaire

Engineering Documentation Methods Questionnaire, North Dakota State University - RF CafeRF Cafe visitor Michael Maassel, an electrical engineering professor in North Dakota State University's Electrical and Computer Engineering Department, requested that I post these few questions to help him effectively prepare students taking senior-level (aka "Capstone") design courses for a real-world experience after graduation. Says the good professor, "The biggest headache I have is getting the students to document their work, both in hardware and in software. Currently, I am requiring that the students use a quad line notebook. This has not been very successful." How do you handle documentation in your every-day work?

Radio Boys Book Series

Radio Boys Book Series, Kirt's Cogitations #323 - RF CafeFor many years Melanie and I have been collecting and reading The Radio Boys series of thirteen books, which were written in the 1920s by Allen Chapman. It was a time in history when the miracle of radio communications was capturing - even enrapturing - the public with its seemingly miraculous ability to convey messages across town and around the world without the need for wires, hence "wireless." The stories center around four teenage buddies, namely Bob Layton, Joe Atwood, Herb Fennington, and Jimmy Plummer (aka Doughnuts") who, with the assistance of a local pastor, Dr. Dale, took an avid interest in radio and built from scratch a successful crystal radio. Their enthusiasm compounds upon itself as adventures and experiences using wireless foster interest in building better receivers and then building transmitters for sending Morse code and audio ("phone"). In order to appeal to his intended audience - primarily young boys - villains, good guys, hapless bystanders, government agents, local law enforcement, family, and even the occasional damsel in distress...

The New Normal - Face Masks Forever

The New Normal - Face Masks Forever, Kirt's Cogitations #322 - RF CafeAbout a decade ago, photos began appearing on news websites showing Chinese citizens walking around wearing face masks in order to filter out the massive air pollution pouring from city factories and coal-fired electric power generation plants. Articles were written advising on the best types of face masks to use while visiting or working in China. The only topic about China competing for shock factor at the time was the rash of suicides at Foxconn as the poor soulless, hopeless workers who build our inexpensive electronics products jumped from upper factory windows and roofs. Since around March of this year, nearly every location in the United States and around the world is looking like China did for the entire last decade. A worldwide pandemic was declared because of a deadly virus which originated from the Wuhan area of China...

Power Equivalent in the Electricity-Water Analogy

Power Equivalent in the Electricity-Water Analogy, Kirt's Cogitations #321 - RF CafeHave I mentioned that my YL, Melanie, decided she would earn her Amateur radio Technician license? After living in a household with a bilingual husband (English and Electronics) for nearly 38 years and having become fairly proficient at ETL (electronics as a third language*), Melanie decided to earn her Technician license. She has never delved into the technical aspects of electricity / electronics, but has, along with hearing me speak of it (too) often and having proof-read my writings and scanned and OCR'ed more than a thousand articles from vintage electronics magazines, her gray cells are permeated with the vocabulary, lingo, jargon, vernacular, slang, and argot of the realm. Being an expert test taker, she will undoubtedly pass the written test with flying colors. With much self-restraint, I have avoided offering my sage advice and knowledge during her studies of the ARRL's Ham Radio License Manual. The current edition is the 4th, being valid from 2018 through 2022. Melanie has asked for a little clarification on SWR, decibels and couple other minor topics, but otherwise has progressed...

The 3D Smith Chart: From Theory to Experimental Reality

The 3D Smith Chart: From Theory to Experimental Reality - R FCafeThe world was introduced publically in 2007 to the concept of a 3-dimensional Smith chart by Chris Zelley. In article published in IEEE Microwave Magazine entitled, "A Spherical Representation of the Smith Chart," the radically new concept was illustrated on the surface of a ping pong ball using a felt-tipped pen (thumbnail at left). Inspired by the sight, Andrei A. Muller and a small team of developers in 2013 created a version of the 3D Smith Chart in software using the Java language that allows it to execute on any platform. In 2017, an expanded functionality commercial version of 3D Smith Chart was released at a very modest price. A number of articles have been published on the topic extolling the unique ability of a 3-dimensional complex impedance volume to expose...


Morse Code in "Western Union" Song

Morse Code in the "Western Union" Song, Kirt's Cogitations #318 - RF CafeThe other day a song entitled "Western Union" played on my local over-the-air oldies radio station. It was released by the group The Five Americans in 1967. I've heard it many times before, but it finally occurred to me that the use of Morse code-like symbols in the refrain made it a perfect candidate for a spot here on RF Cafe. The full lyrics of "Western Union" can be found at the bottom of the page, but notice the "Dah-Dit-Dah-Dit-Dah" repeats in the refrain. Even though I'm a licensed (as of 2010) Ham, my shameful (according to some veterans) status as a post-Morse-code era did not require demonstration of code proficiency. As such, my lack of a Morse code deciphering ability required that I rely on an online translator for considering what the code might be. Depending on how you separate the dits and dahs, the string of characters can be interpreted as TETET (- . - . -), TAA (- .- .-), KA (-.- .-), NK (-. -.-), CT (-.-. -) or other combinations, none of which seem to mean anything in particular...


Buy & Sell Ham Radio Operator Homes

Amateur Ham Radio Operator Homes - Buy & Sell, Kirt's Cogitations #318 - RF CafeA couple years ago a house two streets away had an estate sale after the elderly gentleman who owned it passed on. There was a lot of old amateur radio gear for sale, and most of it had been bought early in the morning, right after the beginning of the sale according to the man's daughter who was on-hand. The newspaper notice mentioned the Ham equipment. In the back yard was a nice 40-foot crank-up tower that was a bit weather-worn, but otherwise appeared to be in good condition. She said that was the first item sold. I didn't ask how much she got for it. The house was to be sold, and they were glad to have the tower gone before listing it on the market. I have wondered in the past when seeing a "For Sale" sign in the lawn of a house with one or more radio towers in the yard how much they would impact the sale price. Some Hams would plan to take...


The Lincoln Vocational Technical Center - A Partial Autobiography - #317

The Lincoln Technical Center, Annapolis, Maryland, Kirt's Cogitations #317 - RF CafeLincoln Vocational Technical Center. One day in late spring of 1973 I found myself walking around the gymnasium of Annapolis Junior High School (AJHS) trying to decide which courses I would prefer upon beginning tenth grade the following fall. It was one of the final days of ninth grade, which had been by far my least happy year in school. Living in Mayo, Maryland, I and my fellow neighborhood ninth graders should have attended Southern Senior High School (SSHS) in Harwood, Maryland, where our predecessors had gone for ninth grade, but overcrowding caused the Anne Arundel School Board wizards to decide that for at least that year, we would remain at AJHS for another term. Historically, kids from my area went to AJHS only for seventh and eighth grades and then switched to SSHS. Annapolis, being the capital city of Maryland, was significantly more urban than the rural areas which SSHS type people were accustomed to. The clientele was much more aggressive in the big city. Sure, we had our "red neck greaser" rowdies in the southern part of the county, but at least their parents would whip them if they got caught getting into trouble. The north county parents, we believed at the time...


How to Remove Clutter from Online Document Displays - #316

How to Remove Clutter from Online Document Displays, Kirt's Cogitations #316 - RF CafeIf you are annoyed by pop-ups and extraneous framework elements and/or SEO (search engine optimization) tracking code accompanying application notes, white papers, and images, and videos, many times you can get rid of them by editing the URL displayed in your browser address bar. Compare the displays in this set of screen captures based on the original URL provided in an e-mail (top) to the one where all the extraneous terms have been removed from the URL (bottom). Note that the yellow highlighted components have been eliminated. Often, I remove that stuff from hyperlink URLs before sending my visitors to websites. Companies don't particularly like me doing that, but doing so helps maintain your privacy. URLs in e-mails are particularly likely to contain appended code that contains one or more "&utm_" parts. UTM is the Urchin Tracking Module introduced by Google Analytics' predecessor Urchin and are now supported by Google Analytics. They typically ....



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