1996 - 2016
BSEE - KB3UON
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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Please click here to view May 2014 homepage archive page 2.
Oscilloscopes are usually the first instrument of choice when scouring for agile or unknown analog or digital signals. Modern oscilloscopes offer impressive functionality, but operating these scopes can be a challenge. As a welcome contrast, the new R&S RTE digital oscilloscopes from Rohde & Schwarz provide generous measurement capabilities, minus the operating complexity. With each sporting a common-sense operating scheme, efficient internal circuit architecture, and flexible, high-resolution touchscreen...
Have you ever heard of a "swinging choke?" I surely hadn't, so my probability of getting Inductance Quiz question number 5 correct was 50% at best. I guessed wrong - just my luck. As a result my score was 8/9 = 89%. Oh, the shame. Maybe you will have a better time of it. Be careful with Q6 as well. Otherwise, if you understand the fundamentals of inductor circuit analysis, you will have no problem.
"Need It? Rent It!" That is what was embroidered on the baseball cap my rental store owner father-in-law used to wear. Sometimes it just just makes sense to avoid the cost of ownership. Advanced Test Equipment Rentals just issued their TEC Talk newsletter for May 2014. It includes hot topics in the tech news world, highlights of new or special function test equipment they have available, and some electronics industry news.
If you are looking for a very thorough treatise on transformers, from AC line frequency up through audio and RF frequencies, but without a lot of formulas to distract you, then this article by Ken Gilmore is it. He begins with the fundamentals of a current setting up a magnetic field, talks about mutual coupling and induction, step-up- and step-down transformers, autotransformers, iron and laminated core transformers, multi-tap voltage and impedance matching transformers, and even touches on the mage-size transformers in electrical distribution system substations. Transformers fundamentally work the same way today as...
AWR Corporation, the innovation leader in high-frequency EDA software, offers a wide range of activities during IMS2014. As a platinum sponsor with its parent company National Instruments, AWR will be demonstrating its newly released V11 NI AWR Design Environment™ in Booth #633 on June 3-5, 2014, presenting numerous MicroApps presentation, hosting a customer appreciation event as well as sponsoring other IMS-related offerings.
Pulse modulation comes in many forms, including pulse position modulation (PPM), pulse width modulation (PWM), pulse frequency modulation (PFM), pulse amplitude modulation (PAM), and pulse code modulation (PCM). In addition to providing a nice introduction to the concept of pulse modulation, author Herbert Kondo covers the basics of each type and then discusses their application in various communications systems. The first time I recall encountering pulse modulation was in the mid-1970s with radio control system for model airplanes. Pulse position modulation was the scheme used in both AM...
USAF radar tech Elbert Cook has completed his scale model of the MPN-13 GCA (Ground Control Approach) mobile radar system that he worked on. It has an incredible amount of detail, including the ASR (airport surveillance radar) and PAR (precision approach radar) antennas, the VHF and UHF radio antennas, navigation hazard light, and even the gin poles that stabilize the trailers against wind forces. Elbert's modeling skills are impressive indeed! Hopefully, this model will someday end up in a USAF museum - maybe at Wright-Patterson AFB.
Now here is a profound ode to one of the most noble of technician genres ever to tweak a receiver front end or to change out a transmitter magnetron - The Radar Man! Some of you know that I worked on airport surveillance and precision approach radar in the USAF, so my bias is established. Hmmm... now that I read the poem more carefully, I realize that it is not complimentary at all. It must have been one of those jealous TACAN or satellite comms techs that wrote it!
The first commercial color television broadcast occurred in 1954 during the Tournament of Roses Parade. By the late 1950s, color television sets were becoming popular in homes, but the price, at around $500, was too prohibitive for most people to afford. In 2014 dollars that is equal to around $4,200, which would allow you to hang a 70" Sharp 3D HDTV on the family room wall. This 1957 article reported that there were only about five major manufacturers (more, actually) making color TV sets, including RCA, Sylvania, Emerson, Westinghouse, Magnavox, Zenith, and Philco. Most or all used a common 21" round CRT. Over the years many television manufactures came and went...
RFtronics develops both turnkey and custom solutions for the RF telecom equipment designers and manufacturers. Currently, our product line includes high power couplers, splitters / combiners and filters between 1 MHz and 3 GHz. Local, ISO certified manufacturing with a 25 000 sq. ft. facility and more than 20 years experience in the RF/microwave design and manufacture. This gives us the best of both worlds, the agility of a small company and the production capabilities of a larger-sized, high-volume manufacture.
"A self-taught signals & electronics hacker from Helsinki, Finland. Fond of mysteries, codes and ciphers, and vintage tech. Absorptions is a blog about my hobbies." That is the tag line for Ms. Oona Räisänen's website. Thanks to QST's "Eclectic Technology" column author Steve Ford for bringing this impressive story to the public. Oona's article tells of her adventure in tracking down the source of a mysterious element of an audio clip from a video of a news station helicopter following a police chase. After multiple efforts, the embedded digital signal was decoded and then confirmed to be accurate by the transmitting equipment manufacturer. It's a quick read, complete with good graphics, that you'll enjoy.
Printed MIMO Antenna Engineering, by Mohammad Sharawi. Wireless communications has made a huge leap during the past two decades. The multiple-input-multiple-output (MIMO) technology was proposed in the 1990's as a viable solution that can overcome the data rate limit experienced by single-input-single-output (SISO) systems. This resource is focused on printed MIMO antenna system design. Printed antennas are widely used in mobile and handheld terminals due to their conformity with the device, low cost, good integration within the device elements and mechanical parts, as well as ease of fabrication.
If you like good old fashion 3Ø, high voltage generator and transformer stories with troubleshooting and analysis, then you won't want to miss this one. Having started my career as an electrician with tech school and field experience, I am always drawn to such topics even though I seldom have a chance to tinker with it anymore. The comments section at the end already has quite a few posts, including responses from the author. There's usually one obnoxious person who wants to demonstrate superiority and call names, and there's one here, too. I give Mr. Hardy a lot of credit for his ability to deal with an aspect of electrical engineering for which he was not necessarily trained in depth.
Here is a short tutorial on how to construct a 1/4-wave stub "trap," or filter to attenuate even-order harmonics from transmission lines, be they antennas or sections of track running on a microwave substrate. The article appeared in a 1960 edition of Popular Electronics.
"Far better an approximate answer to the right question, which is often vague, than an exact answer to the wrong question, which can always be made precise." - John Wilder Tukey, statistician and developer of the Fast Fourier Transform (FFT).
Werbel Microwave is a designer and manufacturer of RF and microwave passive components that operate up to 18 GHz. Products and designs are for the commercial wireless industry, featuring power dividers & combiners, directional and hybrid couplers, bias Ts, and resistive dividers. An expansion is planned for business year 2014 that include high power directional couplers, weatherproofed enclosures, and miniature drop-in packages. Typical turnaround time from concept to manufacture is within four to six weeks after receipt of order.
John H., of Tucson, AZ, is the April winner! He selected Microwave and Millimeter-Wave Electronic Packaging, by Rick Sturdivant. John was not only a purchaser of RF Stencils for Visio, but he also pointed out an error on on of the pages, so he was awarded his choice of a book. Two other people had been notified on May 1 and again on May 3, but neither responded, so they lost the chance. Graciously provided by Artech House
For the sake of avid cruciverbalists, each 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., Hedy Lamar). This particular puzzle has lots of abbreviations and acronyms.
Hide me. My predicament started out as a mere curiosity, but then over time the phenomenon seemed to occur with greater and greater frequency. I tried to dismiss it as being a "coincidence" that was only noticeable because I was subconsciously monitoring and listening for it. After today, however, the time has clearly come to take action. The disturbing events are instances where I am reading or writing a particular word or phase and at the exact same instant I hear that exact word or phrase spoken on the radio. Now, I have to admit that I spend practically my entire waking life either reading or writing, while simultaneously listening to a variety of talk and music radio in the background. Melanie will attest to the alarmingly large number of times I remark...
For over 20 years Z-Comm has employed the latest in proven technology to achieve low phase noise, wide tuning ranges and higher operating frequencies in our VCO and PLL modules. Our state-of-art, high speed SMT manufacturing facility is located in San Diego, CA. Our solutions can be tailored to address any VCO or PLL need with the highest performance available in today's demanding market. Z-Comm can also provide custom solutions for customers with short deadlines.
Hobbyists in the technical realm have in many ways contributed mightily to the advancement of professional scientific knowledge and practice. This is partly because many hobbyists are also career technologists, but the majority are tinkerers, experimenters and otherwise participants who come from all walks of life geographically, economically, professionally, and socially. Just as with university and corporate laboratories, some of the discoveries are the result of structured, preconceived plans of action and designs of experiments with certain goals in mind; many, however, are due to serendipitous events that are recognized by their participants as being significant. Such is the case of 'TV DX' as related in this story. TV DX is the use of...
Dow-Key Microwave is the world's largest manufacturer of electro-mechanical RF switches in coaxial, waveguide, and rack switching matrix formats. We are certified and committed to providing unparalleled customer service, competitive pricing, on-time delivery and products that are distinguished by quality and reliability. Dow-Key offers the largest switch product line in the world with over 10,000 unique configurations.
OK, time again for weekly links to RF and microwave magazine articles. I wish HFE would make their PDF format with bookmarks so I could link directly to an article page, but unfortunately you have to view the online version and thumb through to the page.
Give Science a Boost,
• Möbius Coupling Approach
Drops SMD DRO Phase
Noise, A.K. Poddar,
• The Quirks of Quarks,
• Measure an ADC's Offset
and Gain Error,
A. Chakravarty, S. Jain
• Multiband Doherty
Amplifiers for Wireless
• Jitter and SSN, M. Dunn
• How Trends in Electronics
are Affecting Connectors
(p.22), B. Stanton
The proper care and feeding of vinyl records was - and still is - a big topic amongst audiophiles. As with so many things, phonographs and platters have experienced a resurgence in popularity in the last decade or so as the world gets nuttier and people crave for a simpler, saner time - imagined or otherwise. I remember back in the barracks at Robins AFB, GA, where there was always at least one guy who would have a very extensive (pronounced "expensive") stereo setup complete with an equipment rack, reel-to-reel tape player, dual cassette tape deck, super-sensitive AM/FM receiver with a huge tuning knob on the front, a turntable with a precisely balanced and weighted tone arm (with a stylus that cost two month's pay for an enlisted man)...
Established in 1987, Pulsar Microwave is a supplier of high quality RF and microwave passive components in the frequency range of DC to 85 GHz. Because of our large library of designs, we are able to provide custom products with little effort and in most cases with no additional price increase above the standard catalog item. New products are introduced on an almost monthly basis, the most recent of which are high power directional couplers and power dividers. Coming shortly are high power switches and low power resistive power dividers.
A good technician, knowing what sine-wave signals are simultaneously applied to the horizontal and vertical inputs of an oscilloscope, can predict what the displayed Lissajous pattern will be. In this quiz, the same signal is applied to both amplifiers, but through combinations of impedances that cause differences in the phase angle and amplitude of the actual AC voltages reaching the inputs. All resistances and reactances have the same ohmic impedance at the applied frequency, the gain of both amplifiers is equal, and positive-going voltage deflects the spot upward, or to the right...
API Technologies' Transmit and Receive L-Band Antenna Arrays are designed for military and commercial markets and applications including point-to-point communications, satellite communications, and RF transmitters and receivers. This low profile, high gain, linearly polarized planar antenna array achieves wider bandwidth than similar sized antennas. API utilizes an in-house proprietary mix of substrate materials which allows wider than normal bandwidth for an antenna of this size and frequency range.
I love these kinds of stories. It has the perfect combination of situational humor, irony, and a very important lesson about relying on subjective measurement versus objective measurements. If you have a great tale to tell about one of your work or hobby experiences that no respectable publisher will print, you're welcome to send it to me for consideration in the RF Cafe "Out of Order" series.
While a bit far-fetched, this Carl & Jerry saga has the two amateur radio hobbyists cum detectives applying their knowledge of standing waves and an invention called SNARE (Signal Net for Actuating Radio-sensitive Explosives, by Irwin Ehlmann) to thwart an assassination attempt on a visiting foreign dignitary. The choice by author John T. Frye of a halo antenna on their mobile shortwave rig was probably no coincidence given the guardian angel role it played in the adventure.
AWR Corporation has extended its 2013 ADF tour well into 2014. The final venue stops being added to this tour are located in Israel. Late addition dates and locations include May 20th in Haifa and May 21st in Tel-Aviv. The agenda details as well as registration are all online and available now. AWR Design Forum is a free and open event where designers of microwave and RF circuits and systems can network, share useful information and resources pertinent to high-frequency design, and collaborate on industry issues
"Unprecedented openings for non-engineers result from industry growth and shortage of skilled men." Thus goes the subtitle for a magazine article pitching the promises of a career in electronics technology. It came at a time that predated throw-away everything rather than attempting to repair stuff. It was before the term 'personal device' (aka 'throw-away') had been coined. It was before placards warning "No user serviceable parts inside" were routinely stuck on practically every item purchasable in a department store. It was a time when people took stuff apart to see how it works, and were actually able to figure it out because parts were large enough to see and actually moved, and even printed circuit boards...
Long distance communications (DX) thrives on ionized atmosphere. It causes boundary layers at various altitudes that function as reflecting surfaces and thereby facilitate the 'bouncing' of radio waves off the sky so that they bend around the curvature of the Earth. Early sounding rocket experiments verified that indeed ionized layers of atmosphere did exist as suspected based on theories of aurora activity during periods that correlated with observed solar flare activity. Intense solar flare periods are associated with large numbers of sun spots, since coronal mass ejections (CMEs) are produced which supply enormous amounts of electrons traveling at high speed earthward. CME matter of course shoots in all...
Filter Synthesis Using Genesys S/Filter (Artech House) Hardcover, by Randy Rhea. S/Filter includes tools beyond direct synthesis, including a wide variety of both exact and approximate equivalent network transforms, methods for selecting the most desirable out of potentially thousands of synthesized alternatives, and a transform history record that simplifies design attempts requiring iteration. Very few software programs are based on direct synthesis, and the additional features of S/Filter make it a uniquely effective tool for filter design. This resource presents a practical guide to using Genesys software for microwave and RF filter design and synthesis.
Career and Job Hunting
Advice for May 6, 2014
It's time for another helping of job hunting and career advice stories. There seems to be no limit to the amount of advice available by helpful 'experts.' Many of these particular bits of guidance for your life come from authors on LinkedIn, which typically does have good content. Considering, however, the quality of helpful suggestions offered by your friends and acquaintances in the real world, it would be wise to learn a little about the source before potentially risking your future. With that bit of my own advice in mind...— Is Your Present Job Costing
Innovative Power Products has more than 30 years of experience designing and manufacturing RF passive components. Our couplers, combiners, resistors, and terminations incorporate the latest technology in materials available, which equates to unrivaled product performance. Products include 90° couplers (30 MHz to 4.2 GHz), directional couplers (20 MHz to 6 GHz), combiners (20 MHz to 4 GHz), RF resistors and terminations (DC to 8.5 GHz, up to 800 W CW)
Engineering college rankings for 2014 have been out for a while now, so I'm a bit late reporting the results. All the ranking entities have their own set of criteria and claim to be objective, but unless there is a mutually agreed upon standard, let's face it, they all have a component of subjectivity in the ordering. I'm not going to tackle the validity of methods used, but instead will present the data. Note, however, that it is worth doing a quick read through the stated methods since some are based on institutional research and others rely solely on student surveys. Some rate only schools whose highest degree offered is a Bachelor's, while others include graduate and post graduate schools. Being that RF Cafe is viewed by a worldwide audience, I have included...
Please Thanks Reactel
for Continued Support!
Since it was established in 1979, Reactel has become one of the industry leaders in the design and manufacture of RF and Microwave filters, diplexers, and sub-assemblies. Through a continuous process of research and development, we have established a full line of filters of all types. We offer the generally known tubular, LC, cavity, and waveguide designs, as well as state of the art high performance Suspended Substrate models. We use the latest in CAD/CAM methods and equipment in all of our design and manufacturing processes. We feature a modern, well-equipped machine shop...
The Load Line Story
If you are familiar with Saunder Harris' After Class stories for Popular Electronics, you know they were written in the form of a story that describes a mentor mentoring a mentee (yes, mentee is a real word). "The Load Line Story" presents a quick lesson on how to determine the operational points of in this case a vacuum tube, but it applies equally well to a transistor. If you have had a difficult time conceptualizing the usefulness of I-V curves a load line, then this might be just what you need to get you going. Sure, all the designers out there do this in their sleep, but remember that every day there are new people getting into electronics and this is what they are looking for to help get them on the path to where you are.
IPP Intros New 20-1000 MHz
Drop-in Hybrid Coupler
Innovative Power Products introduces their Model IPP-2247, a 150 watt 90 Degree Coupler in a Drop-In package style that operates from 20 - 1000 MHz. The IPP-2247 will combine two signals up to 150 Watts CW of total output power. This coupler has a remarkable amplitude balance of ±0.25 dB across the whole band. This design is a 3 port device with an internal Termination capable of handling 50 watts. Insertion Loss is less than 0.90 dB, VSWR is less than
Notable Tech Quote
"There are two possible outcomes: if the result confirms the hypothesis, then you have made a measurement. If the result is contrary to the hypothesis, then you have made a discovery." Enrico Fermi. Caveat: This quote is widely repeated on the Internet and in printed material. I could not find an original source, but it sounds good and he could easily have said it considering his other sourced quotes.
Mathematics in Radio
This entry level introduction of differential calculus as it applies to electronic circuit analysis appeared way back in a 1932 edition of Radio News. It was written by none other than Sir Isaac Newton himself (just kidding, of course). Author J.E. Smith created an extensive series of lessons that began with simple component and voltage supply descriptions and worked up through algebraic manipulations and on finally to calculus. I remember not being the best math student in high school (OK, one of the worst), but once I got an appreciation for the power of mathematics for analyzing electronics, mechanics...
RF Engineering Crossword
Puzzle or May 4, 2014
This week's RF Engineering crossword puzzle, like all my crossword puzzles, uses only words that I personally placed into a custom dictionary of words relating to science, mathematics, engineering, chemistry, astronomy, electronics, and other technical fields, plus you are likely to find a few company and engineering schol names that your recognize as well. Contact me if you would like to have your company or school name added to the dictionary terms.
The Broadcasting Goose
"Are we killing the broadcasting goose, layer of many golden eggs?" Dr. Lee de Forest asked in his inaugural address, upon his election to the presidency of the Institute of Radio Engineers. So went the opening editorial in a 1930 edition of Radio News magazine. It was directed at the question of whether excessive, "gratuitous" advertising was going to be so offensive to listeners that they would turn off the set and go back to their former silent worlds. Remember that many, if not most, households, and certainly not automobiles, even had radios at the time. Building an audience was essential to nurturing the new phenomenon of radio, and to saturate the listeners with commercials would surely doom...
PMI Intros 4k W Ppk 1P2T
1.0-1.1 GHz Reflective Switch
PMI Model No. P2T-1G1R1G-25-R-TFF-40W is a single pole, two throw, hermetically sealed, reflective switch designed to operate over the 1.0 to 1.1 GHz frequency range. This model is designed to handle 40 watts average input power and 4 kW peak having a 3usec pulse width and 1% duty cycle. The switch offers fast switching speeds of 300 nsec maximum, low insertion loss of 0.4 dB typically and high isolation of 37 dB typically
Jean Shepherd on Getting His
Class A Radio License - Funny!
Not very long ago I mentioned Jean Shepherd (original asignee of W9QWN and later K2ORS call signs) as being one of my favorite old-time radio broadcasters (1960s-1970s). Jean was famous for recounting stories of his own life and for reporting news of the time in a way that could hold you in rapt attention from beginning to end. His humor, wit, and command of the English language was acknowledged by his contemporaries. If you listen to enough of his broadcasts you will notice the frequent mention of electronics and his experiences as a licensed amateur radio operator beginning at a tender young age. Just recently I listened to him recount his first day in high school when a SNAFU in the computer-generated (must have been a UNIVAC) class schedule mistakenly had him reporting to the girls' swimming pool...
10th U.S. Circuit Court Tackles
Allowing Expert Testimony
This article by Bob Ambrogi, of IMS Expert Services, reports on the 10th U.S. Circuit Court of Appeals' addressing the need for a more objective means for testing whether expert testimony should be allowed during litigation. The action was taken as the result of an IP theft case whereby a software engineer was accused of stealing code from his former company and using it to help start a new competing company. Precedence is given a lot of weight when courts consider testimony and in determining the rules of engagement before the bench. I am innately dubious of simply regarding precedence as settled law because of how often decisions are overturned on appeal. When precedence is used to sidestep the need to make a courageous ruling...
Novel Radio Items
My father used to refer to the "sweet-voiced lady predicting the weather over and over again" as my girlfriend because I would call the 'WEather-1212' phone number (936-1212) so often. It really wasn't because I was infatuated with her voice, it's that I was obsessed with weather forecasting. Most of my free time as a kid and teenager was spent building and flying model airplanes and rockets, and at eighteen years of age I began taking full-size aeroplane flying lessons, so my world revolved around a zone extending from terra firma up to about 5,000 feet AGL. This collection of communications news items in a 1940 edition of National Radio News includes the creation of that very recorded weather forecasting service. Now, I admit to having a bit more of a problem explaining...