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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The inventions and products featured on these pages were chosen either for their uniqueness in the RF engineering realm, or are simply awesome (or ridiculous) enough to warrant an appearance.
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this really puts the "cool" in Cool Product. Marshall Radio Telemetry is a company that makes tracking devices
for falconry and hunting dogs. Transmitters operate on 216.005-219.995 and 433/434 MHz bands, with
line-of-site range of about 60 miles and run times of up to 40 days on some models. 433 MHz models require a
Ham license to use legally.
is supplied by a 3 V lithium cell. Hand-held receivers incorporate a Yagi antenna for direction finding and "a
new polyphase noise floor reduction feature." The entire unit folds into a compact format. Digital processing
has replaced traditional analog methods. These are very impressive products that have been refined to a high
degree. Marshall Radio Telemetry currently has a job opening for a
you love the outdoors and have been dreaming of a chance to combine work and pleasure, this just might be your
opportunity! View the
If you are a Star Wars fan and always wanted one of those hovering Speeder Bikes that Luke and Leia rode during the Jedi woodlands chase, then your wait may soon be over. Aussie inventor Chris Malloy has a prototype model built and is now testing his Hoverbike. The production model will be gyro stabilized and will have safety features incorporated like fully protecting the rider against contact with the propellers. Unlike a helicopter, the Hoverbike will not be able to autorotate in the event of a failure, so a parachute will be necessary. Here are the design specifications: Airspeed Vne - 150 KIAS (untested), Hover (out of ground effect) - >10,000 ft (estimated), Dry weight - 110kg, Max gross weight - 270kg, Total thrust - 295kg, Engine - 80kw @ 7500rpm. If you would like to help finance the Hoverbike, you can donate and have a chance to win a prototype.
I normally reserve this space for products directly related to engineering, but this Livescribe pen idea seemed like a worthy subject for engineers, managers, sales people, and students. Using an IR detector with specially printed paper, Livescribe records not just everything your write, but also an audio recording that is time-stamped to synchronize with what you write. That way, if you are taking notes based on a discussion or presentation, you can tap the pen on the word or drawing you made at the time, and hear what was being said that made you write it down. The pen stores everything in onboard 4 GB or 8 GB RAM than is transferred via miniUSB. Surely a wireless version is in the works. To save money, you can make the special dot-coded paper on your printer, or, you can buy pre-printed paper and notebooks. There are even cool apps for it.
seems these days there is almost nothing that isn't made if you look hard enough to find it. I was reading
about early telegraph (wired and wireless) systems where a coherer was used as the signal detection element.
In fact the coherer, developed by Mr. Marconi, was the first type of detector. As with most contraptions of
the era, it was of simple construction with all macro-scale components. Fundamentally, it consists of metal
filings between two electrodes. A vacuum is needed for longevity of operation, but as the
demonstrates, a vacuum is not necessary. In its untriggered state, the metal filings do not complete a
conduction path betwixt electrodes. When a high voltage from a spark (wireless) or pulse generator exists
momentarily between the electrodes, the metal filings rearrange to form a short circuit. Resistance between
electrodes goes from infinity to near zero. The problem is that the short persists until the tube is given a
tap. Receiver designers solved the problem by arranging for a little hammer to whack the tube immediately
after a pulse is received and recorded. Ingenious. You can buy a new
coherer on eBay for a mere $45. See one in action on
Nathan Bergey, an Appalachian State University alum who studied physics and astronomy, has come up with a light display that illuminates whenever the International Space Station (ISS) is overhead in your location. Says, Mr. Bergey, "Human space flight is an awesome part of living in the future. But why does it still seem so abstract? There are people in space right now! Did you know that? ISS-Notify is a simple attempt at making our space program more real. Many times a day the ISS passes overhead unnoticed. Often it happens during the day when it's too bright to see the tiny dot in the sky. So this light will pulse and shine whenever the station is overhead -- making the invisible visible." The light interfaces with your computer. Kits and fully functional units are available. p.s. I have seen it with binoculars. My soon-to-arrive Celestron 8" catadioptric telescope should provide an even better view.
A huge amount of free software is available on the Internet. It is not hard to find with a good search engine. Most of it comes with a disclaimer warning the user that calculations might be incorrect, and that a user's misunderstanding of the input requirements could produce errant results. Don't let that stop you, though, because if you read the fine print of the kilobuck software, you get the same admonishment. The first place I look is on some of the highly trafficked amateur radio websites like The DX Zone. Here is a page-o-links for antenna simulation software and online applets. The ARRL website has similar products. Likewise for signal propagation calculations. Keep in mind that many - if not most - of the programs are written by engineers and technicians who use the results in their own endeavors. Many of the aforementioned kilobuck software vendors offer free evaluation versions that are perfectly adequate for small projects. Some also have academic discounts for students, so check them out, too.
by what people are paying for collectibles on eBay these days, you wouldn't know the world is in a severe
recession. I have seen vintage airplane and rocket model kits and "firsts" of electronics gadgets that
originally sold for under $25 sell for many hundreds of dollars. This letter dated 1946, from J.B. Dow of the
Navy Department to E.F. McDonald Jr. of Zenith Radio Corporation in appreciation for their contributions to
early developments in shortwave radio, is a little different than the aforementioned cases, but I have seen
these types of documents sell for surprising amounts as well. I have no idea what the intrinsic value of a
document like this is, but an eBay auction might be just the venue to decide. RF Cafe visitor Sam Y., the
proprietor of the letter, wrote asking me to help make its availability known, so here you are.
Disclaimer: I neither endorse nor receive compensation for the article; I'm just here to help.
You might think I am getting desperate for a Cool Product topic when a cooking pot that has a built-in USB port for charging portable devices is featured, but this is more than just a gimmic. TES NewEnergy is a Japanese company that designs and manufactures energy harvesting products that exploit a breakthrough oxide compound material capable of converting heat-waste into electrical energy (Seebeck effect) at temperatures much higher than possible previously. An interesting chart showing the performance of various types of thermoelectric materials as a function of temperature is shown. The pot can recharge a typical mobile phone in 3-5 hours. That's a lot of heat used to provide maybe 1200 mAh of energy, but if you are boiling down tomatoes for canning or grapes for jam, you might as well disconnect from the grid to charge your iPhone. No price is given.
An idea whose time has come? The last year has brought many news stories about how the cell phone service providers are desperately seeking ways to offload some of the data congestion from cell towers to local networks. Data downloads from smartphones now dominates traffic, and has created a near crisis for cellular companies. All current wireless technology is on the table in exploring means to relieve the bottleneck created by relatively sparse cell tower availability. Since operations like texting are often within a small local area, accomplishing the transfer via Bluetooth or ZigBee in offices or school rooms is viable, and for larger venues the use of WiFi networks could be the best answer. In cities around the world where nearly contiguous WiFi coverage is available, such a scheme is very practical. A couple years ago, inventor/consultant Gunther Knapp devised a high efficiency, non-invasive Wall Coupler for WiFi frequencies. He published an article in the May 2006 HFE detailing the design and operation. Maybe it is time for an investment group to consider exploiting this idea!
for smartphones are all the rage. Many product manufacturers are providing apps as part of the package. What
makes this particular app cool is that it is part of a wireless telemetry system offered for remote controlled
models. It used to be that a modeler was satisfied just to have reliable communications from his transmitter
to his airborne receiver. That is especially true these days when the total value of an airplane, engine, and
associated hardware can easily exceed $2,000. The guys who build incredibly detailed scale aircraft that
reflect many hundreds of hours of building, painting, and detailing a WWII era B-17 bomber or a twin-turbine
F-15 model put it all on the line the moment the plane is put in motion. Any failure of the receiver to
properly decode the transmitter's signal can - and often does - result in total loss of all their effort. RF
interference has in the past been the most prominent cause, either from nearby unintentional radiators or from
dopes who switch on their transmitter operating on the same channel (the FCC reserves 50 frequencies
exclusively for airborne R/C). Fortunately for the modeling
Apps for mobile devices cover a lot of ground, but the standard user interfaces can limit the effectiveness of some tasks. Arcade style games is an example. Sure, 4-year-olds who were handed iPads with an image of their portion of the national debt to get them crying (and therefore breathing) upon exiting the womb rather than getting whacked on the posterior, are fully adept at performing any hand-eye coordination exercise with precision, and have no need for seemingly superfluous ancillary devices to extract maximum satisfaction from any software. The rest of us, particularly those of us who grew up with arcade boxes, can appreciate the nostalgic - and maybe even necessary for the dexterity-challenged generation - appeal of this iCade physical interface for the iPad. For me, it brings back memories of Asteroids and Donkey Kong with Don Hicks and Allen Coker at the base bowling alley. Cool indeed, maybe even rad.
Are you in the market for an additional 4 kB of RAM? Are you worried about your computer not working properly if the dreaded EMP event ever occurs? If so, you might be interested in one of these circa 1945 RCA Selectron 4096H memory tubes - aka "memory organs" in the era. This 4x1024 memory is comprised of stacks of plates with eyelets mounted on a mica insulator layer that store charge as electrons are streamed from the cathode. Depending on the potential of the eyelets, they would either attract or repel the electrons, thereby determining whether a "0" or a "1" is being represented. Read, Write, and Signal Out lines are used to determine the bit sense. That means two driver circuits and one sense circuit is required for each bit. See the Selectron Theory page for a full description of operation secondary emission bistability (sounds like a psychology term). Next in the line of memory evolution was the magnetic core memory.