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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 tying up your telephone line, and a nice lady's voice announced "You've Got Mail" when a new message arrived...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

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Remember When ... larger electronics systems companies had in-house machine & PCB fabs?

Today in Science History

Tech Industry Headlines

Tech Industry Headlines - RF Cafe - Archive -

• UK to Pause Smart Motorway Rollout

• 230B Phone Apps Downloaded in 2021

• Beijing Warns Against Helping Olympic Vehicles in a Road Accident

• Compact and Simple Terahertz Radiation Source

• FCC Reaches Major 911 Communications Failures Settlements

• RF Sem Market to Grow by $961M from 2020 to 2025

• U.S. Space Force's New GPS III Variant Capabilities

• What's Next for the World's Supply Chains in 2022?

• Complex Numbers Essential in Quantum Theory

R/C Triplex: 3 Controls on 1 Channel

R/C Triplex: Three Controls on One Channel, November 1956 Popular Electronics - RF CafeThis "R/C Triplex: Three Channels on One Channel" article that appeared in a 1956 issue of Popular Electronics magazine was written by a fellow who was well known in the aeromodeling world at the time - Claude McCullough. Claude won many titles in precision scale for both control line (C/L) and radio control (R/C). As was the case with many R/C modelers of the era, he did a lot of experimentation with transmitters, receivers, and electromechanical devices used to move control surfaces. Rubber-band-powered escapements dominated the field, but some servomechanisms were being developed to provide a means for proportional control and/or a more powerful means of multiposition control. As can be seen in the video I produced showing how a typical escapement worked, the output drove the airplane's rudder to either neutral, full left, or full right deflections, with no position in-between. To actuate the control, the R/C pilot pushed a button on the transmitter the number of times required to affect the desired control movement. That made for somewhat jerky flights, but it was a very popular setup...

Superpower Molecule Could Revolutionize Science

Superpower Molecule Could Revolutionize Science - RF Cafe"When scientists discovered DNA and learned how to control it, not only science but society was revolutionized. Today researchers and the medical industry routinely create artificial DNA structures for many purposes, including diagnosis and treatment of diseases. Now an international research team reports to have created a powerful supermolecule with the potential to further revolutionize science. The work is published in Nature Communications. The researchers describe their supermolecule as a marriage between DNA and peptides. DNA is one of the most important biomolecules, and so are peptides; peptide structures are used, among other things, to create artificial proteins and various nanostructures. 'If you combine these two, as we have, you get a very powerful molecular tool..."

Windfreak App Note: Testing RF Generators for Reliability

Windfreak App Note: Testing RF Generators for Reliability - RF CafeDavid Goins, founder of and chief engineer for Windfreak Technologies, has written a number of application notes pertaining to the specification and testing of RF and microwave frequency signal generators. Most of the articles include features and applications for Windfreak Technologies products, but the concepts are universally applicable. His latest, "Testing RF Generators for Reliability" is featured here. It begins: "We pride ourselves in designing, building, and selling high value radio frequency products that are thoroughly evaluated and tested. All of our products go through rigorous testing before releasing to our customers. Our devices have proven to be very reliable. In rare cases, we have had a product come back for repair caused by output amplifier failures. In this post, we explain the testing process we go through to ensure our high-quality products and the two reasons for output amplifier failures..."

The Semiconductor Diode

The Semiconductor Diode, May 1961 Popular Electronics - RF Cafe"What are these devices?" "How do they work?" "What are their characteristics?" "How are they used?" Those are the kinds of questions about semiconductor diodes posed - and answered - in this article in a 1961 issue of Popular Electronics. Author Jim Kyle runs through a short history of he diode and then delves with more detail into physical construction, I-V curves, power handling, junctions capacitance, resistance, etc. An interesting point mentioned is that while a semiconductor diode will conduct some finite amount of current when biased in the reverse direction (sometimes a desired characteristic), a vacuum tube diode will not conduct at all when reverse biased - thereby making the tube a more perfect rectifier...

Westinghouse "Columnaire" Radio Service Data Sheet

Westinghouse "Columnaire" Models WR-8 and WR-8-R (Remote Control) Radio Service Data Sheet, June 1931 Radio-Craft - RF CafeWestinghouse's motive for dubbing the Model WR−8 the "Columnaire" is apparent when you see a photograph of it. This model also had a −R version with remote control. The remote, though, has a cable attached to it; it's not wireless like today's remote controls. There are some very nice photos of a fully restored WR−8−R version on the AntiqueRadios.com website forum. Look about half-way down the page. Near the bottom of the page is a copy of an advertisement for the Westinghouse WR−8 with a price of $193 (~$3,563 in 2022 money per the BLS Inflation Calculator). The fundamental circuit of these receivers is the WR−5 receiver chassis and power pack shown in Data Sheet No. 29. The model WR−6 is a highboy; its circuit is the same as used in the WR-6, except as modified for tone control. The Model WR−7 is similar to the model WR−6, except as modified for an electric phonograph...

Radio Electromagnetic Spectrum Frequency Bands

Radio Electromagnetic Spectrum Frequency Bands - RF CafeIn response to my solicitation for information on the origin of band letter designations, a website visitor offered this: "I just looked at your web page that gives the names of the various RF bands, and, in one place asked for any information on origins of the names. I have some history on the band names that apply to UHF and above. In the early days of radar (during WWII), the British and the U.S. researchers at MIT chose, arbitrarily I believe, letter designations for radar frequencies. The frequencies that were then possible to use for radio communication were just called by their 'meter range' names: HF, VHF and UHF. The new frequencies that were then only used for deployable radar sets, and for new technology looking for even shorter wavelength radars, were given letter designations. So, in the 1940s and 1950s, radar sets were identified as being UHF, L-Band, S-Band, C-Band, X-Band and K-Band. Later they added Ku-Band - presumably for 'K Upper,' but I do not know..."

RF Cascade Workbook

RF Cascade Workbook - RF Cafe RF Cascade Workbook is the next phase in the evolution of RF Cafe's long-running series, RF Cascade Workbook. Chances are you have never used a spreadsheet quite like this (click here for screen capture). It is a full-featured RF system cascade parameter and frequency planner that includes filters and mixers for a mere $45. Built in MS Excel, using RF Cascade Workbook 2018 is a cinch and the format is entirely customizable. It is significantly easier and faster than using a multi-thousand dollar simulator when a high level system analysis is all that is needed. An intro video takes you through the main features...

Many Thanks for Alliance Test Equipment's Support!

Allied Test Equipment Products - RF CafeAlliance Test Equipment sells used / refurbished test equipment and offers short- and long-term rentals. They also offer repair, maintenance and calibration. Prices discounted up to 80% off list price. Agilent/HP, Tektronix, Anritsu, Fluke, R&S and other major brands. A global organization with ability to source hard to find equipment through our network of suppliers. Alliance Test will purchase your excess test equipment in large or small lots. Blog posts offer advice on application and use of a wide range of test equipment. Please visit Allied Test Equipment today to see how they can help your project.

Amateur Radio Theme Crossword Puzzle for January 23rd

Amateur Radio Theme Crossword Puzzle for January 23rd, 2022 - RF CafeThis January 23rd custom made crossword puzzle has an Amateur Radio theme, compliments of RF Cafe. All RF Cafe crossword puzzles are custom made by me, Kirt Blattenberger, and have only words and clues related to RF, microwave, and mm-wave engineering, optics, mathematics, chemistry, physics, and other technical subjects. As always, this crossword puzzle contains no names of politicians, mountain ranges, exotic foods or plants, movie stars, or anything of the sort unless it/he/she is related to this puzzle's technology theme (e.g., Reginald Denny or the Tunguska event in Siberia). The technically inclined cruciverbalists amongst us will appreciate the effort. Enjoy!

Google's White Spaces Spectrum Database

Google's White Spaces Spectrum Database - RF Cafe SmorgasbordThere are not many technical realms where Google engineers have not either entered or created. Wireless connectivity is key to their continued dominance in the information domain, so they understandably have a vested interest in the "white space" spectrum debate. White space comprises portions of the electromagnetic spectrum where bands are either unlicensed or where licensed bands are or will be up for grabs. An example of the former is the 2.4 GHz Wi-Fi band, and an example of the latter is some parts of the broadcast television band that is being vacated in areas. Although this information is a few years old, it shows how Google was working early−on with the Federal Communications Commission (FCC) to build a real-time database of what they term "dynamic spectrum" in order to provide useful information about available white space (now directs here) to both users and providers. A separate database is available for fixed and mobile spectrum. Enter your location of interest and the map zooms into that region. For instance, in my town (at the time) of Erie, Pennsylvania (see marker on map below), as of January 2013 when this was first posted there were 21 channels available...

Get Your Custom-Designed RF Cafe Gear!

Custom-Designed RF-Themed Cups, T-Shirts, Mouse Pads, Clocks (Cafe Press) - RF CafeThis assortment of custom-designed themes by RF Cafe includes T-Shirts, Mouse Pads, Clocks, Tote Bags, Coffee Mugs and Steins, Purses, Sweatshirts, and Baseball Caps. Choose from amazingly clever "We Are the World's Matchmakers" Smith chart design or the "Engineer's Troubleshooting Flow Chart." My "Matchmaker's" design has been ripped off by other people and used on their products, so please be sure to purchase only official RF Cafe gear. My markup is only a paltry 50¢ per item - Cafe Press gets the rest of your purchase price. These would make excellent gifts for husbands, wives, kids, significant others, and for handing out at company events or as rewards for excellent service. It's a great way to help support RF Cafe. Thanks...

Many Thanks to Reactel for Their Long-Time Support!

Reactel Filters - RF Cafe

Reactel has become one of the industry leaders in the design and manufacture of RF and microwave filters, diplexers, and sub-assemblies. They offer the generally known tubular, LC, cavity, and waveguide designs, as well as state of the art high performance suspended substrate models. Through a continuous process of research and development, they have established a full line of filters of filters of all types - lowpass, highpass, bandpass, bandstop, diplexer, and more. Established in 1979. Please contact Reactel today to see how they might help your project.

Detecting Aircraft at Night

Detecting Aircraft at Night, February 1942 Radio News - RF CafeMost(?) RF Cafe visitors are probably familiar with British engineer John Logie Baird as being considered "the father of television." His work in the 1920s produced both live and recorded motion pictures transmitted and received electronically. What most visitors (including me) probably did not know is that he also developed television apparatus using infrared imaging; he called it "Noctovision." Noctovision (noct or nox meaning night) was a moving image form of the still imaging "Noctovisor," which was an early night vision system that converted an infrared image into an optical image. Radar was still in its infancy in 1942 when this article appeared in Radio News magazine, and had not been implemented widely enough to provided needed surveillance against nighttime bombing raids from Germany's Luftwaffe (air force) flying across the English Channel. According to author Rosen, infrared wavelengths have 16x the fog penetrating power of optical wavelengths...

Thanks Again to Anatech Electronics for Support!

Anatech Electronics logo - RF CafeAnatech Electronics (AEI) manufactures and supplies RF and microwave filters for military and commercial communication systems, providing standard LP, HP, BP, BS, notch, diplexer, and custom RF filters, and RF products. Standard RF filter and cable assembly products are published in our website database for ease of procurement. Custom RF filters designs are used when a standard cannot be found, or the requirements dictate a custom approach for your military and commercial communications needs. Sam Benzacar's monthly newsletters address contemporary wireless subjects. Please visit Anatech today to see how they can help your project succeed. 

China's GalaxySpace to Challenge SpaceX's Starlink - RF CafeTogether with Amazon's Kuiper and the EU's OneWeb, China's GalaxySpace and SpaceX's Starlink will forever transform the night sky by launching tens of thousands of small LEO satellites, each of which will reflect sunlight to observers situated between them and the sun. Many - if not most - will be visible to the naked eye and will definitely appear as streaks in time exposure astronomical images. These systems will provide global broadband connectivity at a projected cost of about $100 per month to those of us who will actually shell out our wampum for it, which is about the cost of equivalent cable-based Internet connectivity now. As is the case now, our expensive subscriptions will continue to subsidize the many who pay reduced rate or nothing for the service - another instance of a few pulling the metaphoric welfare wagon while rest are in it for the free ride...

How the Stereo Disc Works

How the Stereo Disc Works, July 1958 Radio-Electronics - RF CafeMy first major high fidelity (Hi−Fi) stereo system purchase came during my senior year at Southern Senior High School when I had saved enough money to buy a combination AM/FM receiver, 8-track tape deck, turn table, and two speakers with separate woofers, midranges, and tweeters. At the time I thought the setup might impress friends and relatives... until I learned quite quickly that "serious" stereo sound connoisseurs decidedly did NOT have equipment with "Reader's Digest" logos on it. Oh well, the price seemed like a really good bargain to me give the promised tonal superiority. Compared to the clock radio I used previously for my music listening sessions, the Reader's Digest stereo system produced music hall quality sound. Ah, the deep bass notes were grand. Spending most of my earned money on model airplanes, rockets, and my '69 Camaro left little disposable income for LPs (referred to as "discs" in this article), so the turntable did not get much use. I did, however, read up on how to balance the tone arm...

Tiny Sensor Makes the Invisible Visible

Tiny Sensor Makes the Invisible Visible - RF Cafe"A TU/e research group has developed a new near-infrared sensor that is easy to make, comparable in size to sensors in smartphones, and ready for immediate use in industrial process monitoring and agriculture. This breakthrough has just been published in Nature Communications, with co-first author Kaylee Hakkel defending her Ph.D. thesis on January 14th. The human eye is a marvelous sensor. Using three photoreceptor cells that convert visible light into signals for different colors, the eye gives essential information about the world around us. "When our brain puts the signals together, it makes a prediction of what the signals mean based on our experiences. For example, a red strawberry is sweet, but a green one is not..."

Webinar: HF in a Nutshell

Webinar: HF in a Nutshell - RF CafeOn Friday, January 28th and Monday, the 31st, Rohde & Schwarz (R&S) will be conducting a webinar entitled "HF in a Nutshell." You would be excused to thinking that this an amateur radio event because many of the company's employees are Hams, but in fact it is billed as "An overview of current beyond-line-of-sight communications solutions." Further, "HF communications technology is reliable, proven and has been in service for decades. This webinar is the first in a series covering HF topics and will illustrate that HF communications is in no way your grandparents' technology, but rather THE communications solution for the future. You will receive an overview of currently available Beyond Line of Sight (BLOS) communications solutions and the latest developments in this field, i.e. HF versus satellite communications (SATCOM)..."

Low-Pressure Modulation Facts

Low-Pressure Modulation Facts, July 1953 QST - RF CafeAuthor Howard Wright takes the opportunity here in a 1936 issue of QST magazine to distill the concept of modulation down to its basic operation while dispensing with the garbled mix of "graphs, formulas, charts, vectors, diagrams, and Greek letters which often enter into various discussions of modulation." Mr. Wright describes how to the uninitiated radio dial spinner, the culmination of events occurring behind the scenes in an AM reception process is akin to this: "...it might be compared to the reproduction of a color photograph in a magazine. How would we ever know that, to be reproduced, the picture was broken down into its primary colors, if all we had to go by was the original print and the magazine?" That is a very apt comparison...

Bell Telephone Labs - How Do You Stop an ICBM?

Bell Telephone Laboratories - How Do You Stop an ICBM?, December 1961 Radio-Electronics - RF CafeThe era of nuclear weapons of course began in August of 1945 when they effectively ended World War II, but it wasn't until around 1955 that another country - the U.S.S.R. - developed a deployable thermonuclear bomb. Even before that happened, the U.S. Department of Defense began planning for systems to detect and ultimately disable enemy ICBMs and aircraft-delivered nuclear bombs. The nuclear arms race had begun, and continues to this day. Now, there are five countries recognized as possessing thermonuclear weapons, three countries declaring possession, and one country implying possession. A somewhat insane concept dubbed MAD asserts that if everyone can strike and counterstrike with equal capability, that will prevent nuclear warfare because the aggressor will suffer as significantly as the victim. This 1961 Bell Telephone Labs promotion in Radio−Electronics magazine introduced one of the early concepts for intercepting inbound ICBMs. The most familiar and successful system...

Reactivating Leaky Electrolytic Capacitors

Reactivating Leaky Electrolytic Capacitors, January 1956 Popular Electronics - RF CafeUnlike the Roll Your Own Foil Capacitors article in the same issue of Popular Electronics magazine, this one advising how to reactivate leaky capacitors might be of use to a lot more people. The process is called "reforming," and consists of applying a DC voltage to the faulty capacitor, beginning at a very low voltage, and then slowly raising the voltage until the rated working voltage (WVDC) is reached. Doing so, if the capacitor is not beyond rehabilitation, will reconstitute the oxide layer that serves as the dielectric. This particular item was presented as the answer to a question posed by a reader. A Google search on "reform capacitor" will turn up more detail about the procedure. Most people recommend against reforming unless you have no other option, as this writer from India might have faced at the time...

Please see the RF Cafe Homepage Archives for previous items of interest...

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