RF Cafe Software
About RF Cafe
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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This continuation of Part I covering the basics of diode detectors gets into some of the specific circuit configurations and their applications. Author Robert Scott touches on regenerative and superregenerative feedback "tickler" circuits that are able to detect very low level signals. You have no doubt heard of 'quenching,' but how about 'squegging?' The nonlinear devices used in the article happen to be vacuum tubes, so stay away if you suffer from thermionophobia.
Radio Craft Magazine
Sought by Nazi Spies
Just as with the poor, the spies will always be among us. This story reports on a bookstore in New York that during World War II funneled money and technical information back to the Nazi Party in Germany. Electronics, aerospace, and other technical publications (including Radio-Craft) were chief among the sought-after sources. The shop was a front operation that lost a huge sum of money per the official accounting books, but had copious amounts of funds pouring in from German 'investors.' Today's enemy money fronting operations are largely radical...
Peregrine Intros 50 W Power
Limiter Protects 20 to 2000 MHz
RFMW, Ltd. announces design and sales support for Peregrine Semiconductor’s new, adjustable power limiter providing protection for up to 50 W pulsed RF input. For CW applications, the PE45140 handles up to 10 W of power. The adjustable power limiting threshold, from +22 to +32 dBm, enables flexibility across different platforms and architectures. Peregrine’s UltraCMOS, monolithic solution is 8X smaller than comparable GaAs PIN diode solutions
Sherlock Ohms: System
Lockup Stumps Engineer
It seems these Sherlock Ohms adventures go through occasional slumps in the level of profundity and profoundness. Lately, they have been very good, and this 'case' is no exception. Solving difficult problems that can have many possible causes - compounded by being intermittent and not being intentionally reproducible - often involves equal amount of skill and luck. Even the luck part requires the troubleshooter being smart enough to recognize and exploit the good fortune he has encountered. Such is the situation here where fresh-out engineering Alastair Stell becomes a company hero.
Cobham Antenna Systems
Has New MIMO Antenna Range
Cobham Antenna Systems, Microwave Antennas, a leading antenna producer, is proud to announce a new Multiple In Multiple Out (MIMO) antenna range which contains almost 100 antennas. Included in the range are omni, directional, sector, hemi-omni and blade omni antennas, all with at least two connectors. Cobham’s MIMO range makes use of polarisation diversity; vertical and horizontal (V+H), ±45° dual-slant or even right and left hand circular polarisations
for Transatlantic Cable
Who knew that the British Post Office was ever in the vacuum tube development business? This 1957 article about the world's first transatlantic telephone line (TAT-1) mentions that the amplifier and frequency equalizer repeater circuits and components for the Newfoundland and Nova Scotia section of line was their responsibility. Bell Telephone Lab handled the deep-sea portion of the system that ran between Newfoundland and Scotland. Everything was designed to have at least a 20-year service-free lifespan. TAT-1 was inaugurated September 25, 1956, and was decommissioned in 1978 without any technical failures, thus achieving its designed longevity...
Free Engineering Magazines
& Career Advice
These publications are free for the asking... and I make a few pennies on each one to boot. Thanks.
The Jodrell Bank
Radio astronomy has been the motivation for much research work in the design of low noise, high sensitivity receivers, but also in determining the characteristics of the Earth's upper atmosphere. Before sounding rockets could be launched to verify theoretical proposals, observed versus predicted behavior in radio signals being reflected off the moon and planets needed to be explained and, if necessary, corrected for. One notable example of atmospheric perturbation is the rotation of polarization caused by electrons in the ionosphere (the Faraday effect). Parametric and cryogenically cooled receiver front end technology has been primarily driven...
It's a little difficult to make out the shape within the crossword puzzle grid, but it appears to be a transistor schematic symbol. Unlike the weekly RF Cafe crossword puzzles, not all of the clues and words are specifically related to science and engineering, but a large percentage of them are. Admittedly, I have the advantage of a software program to help place the words within the grid. Doing it by hand is a lot more work. I can't imagine how the people who created the New York Times' Sunday-size puzzles were able to do it without computer assistance!
Empower RF Systems
"Live" at EMC 2014
Empower RF Systems is once again conducting live demonstrations of broadband, high power amplifiers with compelling performance, industry leading small size, and user interface / functionality that dares to challenge legacy products offered in the market. Next appearing at EMC 2014 in Raleigh (Booth #311), we will be highlighting two different models - both covering 20 to 1000 MHz - 1 kW in a 5U chassis and 500 W in an even smaller, 3U chassis
Featured Book: EW Receivers
& Receiving Systems
Electronic Warfare Receivers and Receiving Systems, by Richard A. Poisel. Receivers systems are considered the core of electronic warfare (EW) intercept systems. Without them, the fundamental purpose of such systems is null and void. This book considers the major elements that make up receiver systems and the receivers that go in them. This resource provides system design engineers with techniques for design and development of EW receivers for modern modulations in addition to receivers for older, common modulation formats. Each major module in these receivers is considered in detail...
Aviat Networks Looking for
a Product Engineer
Are you looking for an exciting opportunity working for a Global Technology Leader? At Aviat Networks, we take great pride in hiring a workforce that is committed to supporting and strengthening our values and attributes. If you're a results-oriented, customer centric and innovative thinker who also takes pride in personal and professional integrity, Aviat Networks is the ideal next step in your career. We are looking for a Product Engineer loves to solve problems, enjoy change and know how to have fun so come and join a dynamic team that strives to bring communications to the world
Measurement System (dB-FMS)
Here is a million dollar idea for you to consider. I hereby dub it the "Drone-Based Field Measurement System™" (dB-FMS™). The concept came to me while reading a column in QST magazine discussing the use of the EZNEC antenna radiation pattern prediction software. As you know unless a antenna is situated in a perfect, unobstructed environment like in the middle of a desert with a perfectly uniform ground or on a space-based platform, physical obstacles and variations in surface conductivity can significantly alter the 3-dimensional field distribution. Columnist Joel Hallas is a master at EZNEC and is routinely called upon to model antenna systems for people. As important as length and orientation of antenna elements are, the ground plane configuration can have a profound impact on the radiation pattern...
Dr. Stephen Maas Receives
MW&RF Living Legend Award
NI (formerly AWR Corporation) congratulates Dr. Stephen Maas, who recently received the 2014 Microwaves & RF Living Legend Award. Maas was presented the award at the 2014 International Microwaves Symposium in June in Tampa, Florida. Maas, chief scientist of AWR Group, NI and founder of Nonlinear Technologies, has an extensive background in low-noise and nonlinear microwave circuits and systems. He is a prolific author and educator and has authored several books, including Microwave Mixers, Non-Linear Microwave Circuits and Practical Microwave Circuits. Maas has also held
Notable Tech Quote
for July 29, 2014
"Say again." That phrase is heard often in telephony conversations both wired and wireless. It was coined near the end of World War II by Air Corpsman 2nd Lt. Byron A. Susan, as reported in the January 1945 edition of Radio Craft magazine. Lt. Susan was responsible for setting standards for "radio phraseology" to eliminate ambiguity between aviators and ground forces. "Say again" replaced "Repeat" because the latter is an artillery term used to order the repeat of a gun salvo.
Half Century of Electronics
Publishing: Coherer to Spacistor
The iconumerator (electronic particle counter), the vidicon tube (TV image recorder), the Electro Importing Co.'s Telimco (world's first home wireless outfit), the Wireless Association of America (founded before ARRL), the Dynamophone (voice-activated switch), the "Swatties" (members of the Society of Wireless Telegraph Engineers), the "Detectorium" (silicon crystal detector), Ralph 124C 41+ and his sweetheart Alice 212B 423 (Gernsback sci-fi series) were covered. Radio Amateur News predated QST as America's premier magazine for Hams, the famous 1919 "Verboten" cartoon (protested limitations on private radio operators from the wartime era), the de Forest "Oscillion,"...
Sperry Gyroscope Company Ad
"Klystron" Bestowed to Public
Klystron is a household word these days - literally - since every microwave oven contains one. Do you know who registered the trade name originally? Per this advertisement from a 1945 edition of Radio Craft magazine, Sperry Gyroscope Company did. It was actually scientists at Stanford University (Russell and Sigurd Varian) who developed the klystron tube, financed by Sperry as part of its blind aircraft landing system. In an act of magnanimity that would never be considered in today's competitive markets, Sperry issued the following statement: "From now on, the name Klystron belongs to the public, and may be used by anyone...
July 27, 2014 Wireless
Engineering Crossword Puzzle
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).
The big graphic with Figures 1 through 17 reminds me of the kinds of study sheets I used to make when cramming for exams in my college circuits courses. Did I ever tell you about the wise guy instructor I had for my first Circuits class at the University of Vermont? Anyway, this article provides an introductory level treatment of using negative feedback in amplifier circuits. Lots of illustrations and formulas are included. Frequencies are at baseband, so you won't learn any secrets for high frequency amplifier stabilization, but then even RF and microwave circuits eventually need to convert down to baseband at some point for sampling or for use as audio or video.
Magazine Article Update
for July 25, 2014
I think I skipped a week with RF an microwave magazine article updates. Those things multiply like rabbits, so there have been a slew published since last time. Here are just a few highlights:
• Method Eases
System Jamming, D. Pan,
N. Cheng, Y. Bian
• Overview of RF Switch
Applications, P. Bacon,
D. Fischer, R. Lourens
• Waveguide Filters: New
Design Techniques for
Exploiting a Mature
Technology, A. Trusler
• Seeing Jitter in an Eye
Diagram, J-J. DeLisle
• Broadband Chokes for Bias
Tee Applications (p.56),
• Simulating Antenna
Measurements in an
D. Campbell, G. Gampala,
M. Vogel and C.J. Reddy
Did I ever tell you about the guy I had for my first Active Circuits class at the University of Vermont? He was a real wise guy. During those first few weeks our overloaded brains were bombarded with equations and Bode plots and parameter names and circuit configurations, so the anxiety level was very high. That was in conjunction with the same scenario in four or five other classes; you probably know of what I write. A typical class consisted of Professor Anderson beginning in the upper left corner of the chalk board and writing at Olympic speed as he progressed to the extreme lower right corner 50 minutes later...
Electronics Themed Comics
Here are a few more comics from magazines of the days of yore. It is rare to find a comic in a technical or hobby magazine these days. I don't know why that is. Enjoy.
Rosenberger Micro-RF Test
Switch Connector by RFMW
RFMW, Ltd. announces design and sales support for Rosenberger’s 15K101-40ME4 Micro-RF test switch connector. The 15K101-40ME4 Micro-RF test switch is an ultra-miniature (1.8 mm x 1.9 mm, height 1.5 mm), low-cost, surface mount, coax "switch" connector for the verification of antenna/circuit performance in any kind of small device. The connector can be used for applications that require a low-cost, SMD, coax, point-of-entry to a PCB and/or a switch for temporarily disconnecting the on-board
A Decibel Nomograph
Yes, it's another nomograph. This one is for calculating the number of decibels required to amplify or attenuate a voltage level. The chart came from a 1945 edition of Hugo Gernsback's Radio Craft magazine, but decibels are still defined today the way they were nearly 70 years ago. A hard copy of a nomograph residing in a notebook or on the wall is still a handy tool when you need to do a quick calculation. Unless you have a voice-commanded app where Siri will instantly respond with a conversion for you, printing out one of these nomographs might be a really handy aid...
Research at the Threshold
Atmospheric scientists suspected as recently as early 1957 that Earth's upper atmosphere (ionosphere and beyond) temperature might be around 1,000° K. I say 'suspected' because we had not yet launched instruments there to make actual measurements. Soundly posited and agreed upon theory was validated a short time later when sounding rockets reliably reported a maximum of about 1,300° K in the upper ionosphere. We did not know for sure what electromagnetic wavelengths and their respective energy densities would be outside the protective layers of gases encompassing Earth. Much more was known about the depths of the planet's oceans than of its atmosphere. Scientists knew that life was abundant...
Anatech July 2014 Newsletter
Anatech Electronics, a manufacturer of RF and microwave filters, has published its July 2014 newsletter. As always, it includes both company news and some tidbits about relevant industry events, regulations, and standards. This month, Sam Benzacar offers his views on the subjects of power line EMF exposure, microwave device market growth, LTE TV, GM's LTE in-automobile hot-spot, and switching consciousness on and off. He also has a short article titled, "Curing Interference: Never Too Late."
Career News & Tips
It's time for another round of job hunting and career advice stories. There is no limit to the amount of advice offered by helpful 'experts.' Many of these particular bits of guidance for your life come from authors on LinkedIn, Monster, Money, etc., which typically do 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.
Thanks Once Again to
ATEC for Support!
Advanced Test Equipment Rentals provides the latest models of test and measurement equipment from top name manufacturers like Agilent, Fluke, Anritsu, R&S, Tektronix, and Yokogawa. Our primary focus is providing a complete rental solution of test and measurement equipment to industries such as aerospace, defense, EMC, and communications.
Chalco Paper Tape Reader
Restoration by Mark Blair
RF Cafe visitor Mark J. Blair (NF6X) wrote to let me know about the Chalco Paper Tape Reader that he procured and restored. The Chalco unit was used in the TPN-19 ground-based mobile airport surveillance and precision approach radar. Mark would appreciate being contacted by someone who actually worked with the reader on the TPN-19. Mark has a very interesting website that you might enjoy. Says he, "I like to collect, restore and play with military surplus equipment, and that's mostly what this web site is all about."
Finance for Engineers
Finance for Engineers: Evaluation and Funding of Capital Projects, by Frank Crundwell. I saw this book over on the EE Times website and figured it would be a good subject for my Featured Book spot. With flair and an originality of approach, Crundwell brings his considerable experience to bear on this crucial topic. Uniquely, this book discusses the technical and financial aspects of decision-making in engineering and demonstrates these through case studies. It's a hugely important matter as, of course, engineering solutions and financial decisions...
Unlocking the Mysteries
of Radar - AOC Webinar
July 22 from 4-5 pm EDT.
There is still time and space available to register for this afternoon's webinar presented by Fernando C Gonzalez. This interactive journey, from the humble electron all the way up to the self-driving car, explores sound and light, size, wavelength and frequency. Overview of the history and evolution of radar. From the origins of radar prior to WWII, through pulse Doppler, CW, monopulse radars, and to modern active electronically scanned arrays (AESA), the attendee will understand the fundamentals of how radars work. A 10-15 minute Q&A follows.
National Union Radio Corp. Ad
- Women Engineers Needed
National Union Radio Corporation was ahead of its time in terms of hiring women engineers. Admittedly, they and all other manufacturers were dealing with a shortage of male engineers due to the ongoing need by the military for fending off the scourges of fascism, Nazism, communism, socialism, and all the other 'isms' of the day that threatened to overtake the world. However, they should receive due credit for going out of the way to promote the sciences as careers for the fairer gender. The advertised positions required the successful applicant to have earned a bona fide degree in physics, electrical engineering, chemical engineering...
Notable Tech Quote
"It is difficult to say what is impossible, for the dream of yesterday is the hope of today and the reality of tomorrow." - Dr. Robert Hutchings Goddard
Carl & Jerry: Tussle
with a Tachometer
This is a great example of how Popular Electronics and John T. Frye used the "Carl & Jerry" series to teach some basic electronics design principles through story telling. In this adventure, the guys decide to build a tachometer from schematics they found in a magazine. They debate amongst themselves how the circuits works, the best way to assemble the circuit, component selection, vibration- tolerant mounting, and how to properly calibrate the tach to accurately display engine revolutions per minute.
NI's Analyst Update Reduces
Simulation Times Up to 70%
NI (formerly AWR Corporation) has released V11.01 of the NI AWR Design Environment™ with enhancements to Analyst™ 3D FEM EM simulation engine that cuts simulation times by as much as 70% over previous versions. The updates in V11.01, which are specific to Analyst, include algorithm reformulations/enhancements to both automatic mesh refinement (AMR) and fast frequency sweeps. For high-port-count designs (10+ ports), the speed improvements seen with Analyst are the most pronounced
Newly Announced K-1B Visa
for High Tech Workers
Someone had to take the initiative to launch an improved high-tech immigrant worker program. Accordingly, I took the liberty of creating a K-1B Visa for high technology workers. Congress has not officially written it into law, but American politicians and executives make no pretense of enforcing law they disagree with anymore, so it really does not matter. Here is how the K-1B Visa program works: It is widely known that the United States now considers itself to be a country without a southern border. All anyone needs to do to become an accepted American citizen (the new definition, not the old) and enjoy all the freedoms guaranteed by our Constitution (well, except the parts...
Dave's & Bill's Garage
Restoration (HP Beginnings)
Even though you would never know by today's Hewlett Packard (HP), the company's roots are in electronics test equipment (never thought I might have to explain that!). Most people who have been in the electronics realm are familiar with the story of Dave Packard and Bill Hewlett starting their business in the 12'x18' single-car garage where Dave and his wife lived at 367 Addison Avenue in Palo Alto, California. Bill, yet a bachelor, moved into the garage in 1938 (an early entrepreneurial engineer trend setter who literally lived in his office). Their first commercial product was the Model 200A Audio Oscillator. Hewlett Packard went on to become the world's foremost maker of electronic test equipment for communications, medical, basic research...
TV DXing, and the
Dog on the Roof
Because I was born in 1951, I grew up without the benefit of 1,000 cable channels available whenever I wanted them. This was during the 1950s and 1960s when we lived in the city of Pittsburgh, PA. Instead we had to make due with four - that is four - VHF television stations that we could receive on a black and white TV (actually it wasn't strictly BLACK and WHITE; there were various shades of gray). There was one TV station for each network: CBS, ABC, and NBC, plus one 'Educational' (PBS) station. Later on, we got two independent UHF stations. This was also the era when the 'blackout rule' was largely in effect for sports broadcasts, and if you didn't go to the stadium for a home game...
Please Visit PMI in Appreciation
of Their Ongoing Support
PMI's organization has been setup to design, develop, manufacture, test, and market complex state-of-the-art hybrid RF MIC and MMIC components, supercomponents, and subsystems. Unique products for applications in space, military, commercial, telecommunications, and consumer electronics systems. DC to 40 GHz.
Empower RF Awarded Patent for "Broadband Linearization..."
Empower RF Systems is proud to announce the approval of a patent on "Broadband linearization module and method." New communication services and the use of complex waveforms have created a demand for highly linearized power amplifiers. Deviations from linearity show up as spectral distortions and/or modulation quality degradation (EVM) in the output of these amplifiers -that is, undesired energy, not contained in the original signal, inside or outside
Apollo 11's 45th
Anniversary Crossword Puzzle
"Houston… tranquility base here. The Eagle has landed." Where were you 45 years ago when you heard on radio watched on a B&W TV like I did as Apollo 11's 'Eagle' lunar module touched down on the moon - with less than 30 seconds of fuel remaining? A short while later Neil Armstrong and Buzz Aldrin became humans #1 and #2, respectively, to step onto the lunar surface. "We came in peace for all mankind," was plaque attached to the part of the lunar lander that stayed behind. Poor Michael Collins had to be content with orbiting the moon while is shipmates went to the surface. I created this special crossword puzzle this morning to commemorate the Apollo 11 mission...
A few new terms have been added to the transistor lexicon since 1958, but this list from Radio-Electronics magazine contains more than 150 definitions that are still useful today. It is amazing that this list was created just a decade after the transistor was invented, and now half a century later the mot commonly used terms have not changed much. In looking over the words, there are very few that need to be added to the original (which I did).
Custom Interconnects 40 GHz
Test Reports for Fuzz Button
Custom Interconnects announced the release of the most detailed RF characterization conducted to-date on their flagship Fuzz Button® technology platform. The reports are geared towards 50 Ohm impedance matching at high frequencies and include bandwidth measurements, S-parameters and VSWR, as well as SPICE Models. The reports were released as a follow-up to the recent IEEE IMS held in Tampa and are expected to draw a great deal of interest from the RF design community who were eagerly awaiting their arrival
Many Thanks to MECA
Electronics' Ongoing Support
Since 1961, MECA has served the microwave industry specific to passive components in the DC to 20 GHz frequency range. MECA serves all areas of the RF / Microwave industries including world class network providers, and supporting supply chain infrastructure. We have long been the "backbone" of high performance wired and air-interfaced networks such as in-building, satellite, radar, and mobile communications.
News from the IRE 1958 Meet
The International Microwave Symposium (IMS) is arguably the largest single annual event for radio and microwave engineers. According to IMS2014 event officials the show in Tampa, Florida, boasted of a 7,500-visitor attendance. European Microwave Week (EuMW) runs a close second place at around 7,000. In 1958, 55,000 engineers attended the Institute of Radio Engineers (IRE - eventually became the IEEE) in New York City. IMS and EuMW would love to have numbers like anywhere near that. Maybe the large number of attendees was because dissemination of information was not nearly as instant (or eventual for that matter), and the absence of the Internet or...
Raytheon Radio Tubes Ad
I love these old electronics company advertisements from the World War II era. It represented a time when minor differences between citizens were put aside for the good of the country (yours and mine). Nationalism had not yet been redefined by one-worlders to mean that you hated the rest of the world, but rather that you had pride in your country of birth - or legally adopted new country - and were willing to sacrifice for the common good to preserve your way of life. The U.S. and Great Britain were indisputably the leaders in technical invention amongst the Allied powers. Germany and Japan led...
BeRex Adds New Family of High
Performance MESFET Chips
BeRex, Inc. has begun shipping a new family of GaAs MESFET chips, the BCF-series, which addresses the need for low phase noise with high gain and power in applications such as single and multi-stage amplifiers, oscillators, synthesizers, etc. ranging in frequency from DC to 26.5 GHz. The BeRex BCF-series of MESFET chips are ideally suited both broad band and narrow band applications from DC to 26.5 GHz. Typical application requires a high level of OIP3 linearity
How to Use Radio
Short wave radio was a boon to both professional and amateur radio operators because of its ability to be received over longer distances using significantly lower transmitter power. The problem was (and still is) that short wave bands typically suffer from atmospheric ionization effects that vary depending on time of day, local weather, solar activity, pollution, and other phenomena. Long wave's advantage was that although it required higher power and longer antennas, it was (and is) extremely reliable. For other than the most critical applications, idiosyncrasies of short wave communications were accepted as the price of more convenient and lower cost operation. Widespread adoption of short wave communications brought extensive studies and characterization...
MECA Low PIM Components
& D.A.S. Equipment Catalog
MECA* Electronics' new 12-page catalog features many our extensive line of
low PIM RF/microwave components with industry
leading performance including RF loads, attenuators, directional couplers, power splitters, divider/tappers, adapters, jumpers
and D.A.S. equipment.
* Microwave Electronic Components of America
Top U.S. Defense Contractors
Washington Technology magazine just published its 2014 ranking list for the top 100 defense contractors based on the value of contract dollars*. It should come as no surprise that Lockheed Martin leads the pack ($10.4B) by a factor of nearly two over the runner-up Northrop Grumman ($5.87B). My Top 10 list below has the companies listed by value of defense contracts, whereas the original list ranked by total dollar value inclusive of both defense and non-defense contracts. Two companies in the list, Leidos (security) and Fluor (construction), are unfamiliar to me. The other eight design and manufacture a mixture of electronic, mechanical, and software products for military and aerospace customers. The CBO reports that defense spending...
Radio Frequency System
Architecture and Design
Radio Frequency System Architecture and Design, by John W. M. Rogers, Calvin Plett, and Ian Marsland. Communication devices such as smart phones, GPS systems, and Bluetooth, are now part of our daily lives more than ever before. As our communication equipment becomes more sophisticated, so do the radios and other hardware required to enable that technology. Common radio architectures are required to make this technology work seamlessly. This resource describes practical aspects of radio frequency communications systems design...
Dilbert CEO Photo Flash
The July 15, 2014, Dilbert comic strip features the CEO of his company suggesting that they figure out a way to insert ad images into "that little spot" that stays in your vision for a few seconds after someone takes your picture using a camera flash. I wonder whether creator Scott Adams realizes that he might have come up with a patentable idea? Too late. By now the folks at Google or Apple have seen today's strip and have their staff patent lawyers frantically generating applications as I write this. Subliminal advertising has been around for a long time, and it might even be illegal in some countries, but it is not illegal...