RF Cafe Software
About RF Cafe
1996 - 2022
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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These images have been chosen for their uniqueness. Subject matter ranges from historic events, to really cool phenomena in science and engineering, to relevant place, to ingenious contraptions, to interesting products (which now has its own dedicated Featured Product category).
Cool Pic Archive Pages
is a great illustration of teamwork and amazing talent. Shortly after the 9/11 terrorist attacks, Tibetan
monks came to the Smithsonian Asian art museum to create this sand mandala. They sketched the outlines using straight
edges and a compass, then the team laid down colored sand sometimes grain by grain. The intricacy and sophistication
of the pattern reminds me of a fractal.
Too bad at the end of the project they brushed it all away and dumped the sand into the Potomac River.
If you are a football fan, you probably already know about the 49x22 meter displays comprised of 10.5 million LEDs, drawing 635 kW per display. There are two of those plus two 15.5x9 meter displays drawing 80 kW each. That amounts to 1.352 MW, or about the equivalent demand of 2,200 U.S. homes. I'm not complaining. I think it's pretty cool (or, hot), but I guarantee there are a lot of eco-nazis in the stands who are willing to overlook the eco-terrorism being perpetrated in order to have a close-up look at the game action.
If you think this is a Rorschach ink blot test, you would be wrong. If you think this is the first ever CCD image of the surface of the moon, you would be correct. The 100x100-pixel array (0.01 Mpx), used in 1974 to capture the image, was real breakthrough technology. A kid's toy digital camera takes better pictures than this through a cheap plastic lens - in color. Relatively simple, dependable, and inexpensive CCDs have replaced photomultiplier tubes in astronomical imaging applications. Amateurs can buy incredibly high quality CCDs for their backyard telescopes for about $1k.
nothing sacred? Are no laws absolute and immutable? Apparently. Remember learning
(Maxwell's equation stating the sum of the magnetic flux across a closed surface = 0;
i.e., no magnetic monopoles)? If I had turned in an EM exam paper with a result asserting ≠ 0, it would surely
have been marked wrong. The image above shows a material called spin ice (crystalline Dysprosium titanate
Dy2Ti2O7), where at close to absolute zero it acts as a 'frustrated magnet' and permits magnetic monopoles. Now
I am wondering whether 20-some years later I can have any of my tests re-graded?
First there were the Mandelbrot equations and their associated 2-D images, otherwise know as fractals. Now we have the Mandelbulb, a 3-D version that basically takes a Mandelbrot and rotates it about the z-axis. Oddly enough, it was not until around 2007 that serious efforts to perfect the equations were completed. Generated structures range in appearance from biological to ghoulish to just plain weird. Beauty is in the eye of the beholder.
Nixie tubes were sort of the pre-solid-state version of 7-segment LEDs. At 2.75" x 1.5" x 1.2", it is not much larger than a multifunction sports watch. CMOS TTL circuits drive the display - no μprocessor. The only "modern" feature is the use of surface mount components on the PCB. Two 1.5 V coin cells power the nixie tubes via a voltage multiplier circuit, and will last about 6 months if the display is turned on a few time per day.
you remember when most PCs came with 640k of RAM - total? 1 MB required a special expansion board. Here is a section
of the 32 kB 'rope memory' that guided Apollo 11 to the moon and back. It was woven by hand by the dedicated workers
(mostly women) at Raytheon. Guidance, systems monitoring, user interface, and attitude control software shared it
for temporary data storage. It is innately rad[iation] hardened.
Perhaps you have already seen this. In case you have not, here is the picture making the rounds this year titled, appropriately, "The Best Christmas Decoration Ever." Some have questioned the authenticity of the image, but its veracity has been confirmed by Snopes (although Snopes has been wrong). Regardless, what a riot it must have been for the homeowner as he watched passersby freak out over it.
News of the catastrophic Russian hydroelectric power plant failure last August made just a brief appearance. On August 17, 2009, the Sayano-Shushenskaya dam on the Yenisei River suffered a breech that flooded the turbine room, causing at least 1 transformer explosion (see video) and extensive damage to all 10 turbines, destroying at least 3 of them. 74 workers are known to have died in the accident. 40 tons of transformer oil were spilled into the river. These pictures show the incredible magnitude of damage, and the seemingly insurmountable work that will be needed to clean up and restore the plant to operation.
14 km west of Denmark in the North Sea, Horns Rev Offshore Wind Farm is one of the world's largest water-based wind
farms. 80 wind turbines produce up to 160 MW, creating enough power for 150,000 households using 4,000 kWh per year.
This photo demonstrates how downwind turbines can lose efficiency due to turbulence caused by upwind turbines -
as much as 20-30%. I am a big alternative energy fan, but still not entirely convinced that in the long run they
are anywhere near as efficient $-wise as nuclear, hydro, or coal power.
A group of engineers are volunteering their time and expertise to restore an IBM 1401 computer for the Computer History Museum. Says one, "It's a mechanical machine: The tape machine has an air sensor, a little rubber diaphragm with contacts on it, and you can see it work. With these modern computers, it's just magic—they've got things a few nanometers long, and you'll never see them." Sporting a magnetic core memory, the 4-ton system has about one-millionth the computing power of a $600 desktop PC.
It seems that just about anything can be trademarked these days. This very interesting chart demonstrates the importance of color selection when choosing a corporate logo. Many of the most well-known tech companies are placed on the spectrum line according to logo color. The article points out that T-Mobile (Deutsche Telekom) has trademarked the color magenta. UPS owns the word and color "brown" and Orange owns orange in their respective realms. Given that the color spectrum is continuous, trademark law must somehow specify how far apart colors must lie in order to not encroach ownership.