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 ...
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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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
wrong with this picture? Believe it or not, that is how my former USAF buddy, Jim Flinn, of
Flinn Engineering, found
this connection for an AM broadcast station that he and his team were called in to fix. Per Jim, "Before we started
you couldn't hear this 1000 watt AM radio station five miles out of town. After we were done it could be heard 50
miles away." Paying advertisers probably were not happy about the 5 mile range since their audience would have been
reduced considerably. It is a wonder that the transmitter even survived what must have been an atrocious mismatch.
The photo is not detailed enough to show the intricacies of the center conductor connection, but the ground/return/shield
connection is nothing more than a piece of copper wire bolted to the coax feed cable shield. So, in addition to
the awful return loss, the potential for PIM (passive
intermodulation) generation is enormous. I'm guessing if a spectrum survey of the tower output had been conducted,
it would have shown a huge blob of crap all around the carrier that would have warranted a severe violation issuance
by the FCC. A lot of times, those kinds of problems are first noticed and reported by listeners of AM radio that
pick up <more>
"Will It Blend?" Fuggedaboutit. The real question is, "Will it survive a fall from 13 kilofeet?" This iPhone 4 did. He did not say how high he was when it left his pocket, just that the jump began at 13,500 feet (could be like the old joke about falling off a 20' ladder - from the bottom rung). According to its skydiving owner Jarrod McKinney, the phone came out of his pocket during a jump. He found the phone, using a GPS tracking app, on top of a building about a half-mile away from where he landed. The fact that the app even located the phone showed it was still working. The really amazing thing is that the phone had cracked a bit when his young son knocked it off a bathroom shelf. So the lesson learned here it that the iPhone 4 can continue to function under just about any condition ...other than holding it in your hand the wrong way!
Some people take to heart that funny sign posing the question, "If a cluttered desk is an indication of a cluttered mind, then what is an empty desk an indication of?" EE Times recently published a collection of photos submitted by readers of ultra messy work areas. I have worked at a lot of companies and have seen a lot of messy offices. Photo #3 is typical of some of the messier habitats I have seen. One staff engineer at a defense electronics contracting company had a huge office that must have had every piece of paper, proto board, component, software, book, catalog, and datasheet he ever owned, dating back to about 1960. When the guy retired, the place should have been enshrined and admission charged for nostalgic tours. I was a real slob as a kid, but somehow a stint in the USAF turned me into a neat freak. Unless you have a photographic memory for remembering where everything is, no matter how much time passed since last using it (as Bob Pease reportedly did), organization tends to work best.
recently published an interactive map of Venture Capital activity for the first six months of 2011 in the U.S. The
northeast corridor, Silicon Valley, and southern California are, as usual, the main benefactors of the investments.
The map represents 1,500 venture-capital funding deals spread across 40 states, worth more than $14B. If you click
through the various business categories, Healthcare is by far the largest area of investment. It shows how companies
are gearing up big-time to take Federal money from the impending socialization of the healthcare system. IT, the
next largest, is a big part of the socialized medicine scheme as well. Energy and Utilities is likely dominated
by people getting in on all the government funding of green technologies - many of which are failing even now after
receiving collectively billion$.
Interestingly, there is no separate category for electronics and software other than maybe being lumped in with the Consumer Goods category. I did not find the map to be particularly useful otherwise; maybe you will.
RF Cafe visitor and RF Coffee Mug winner Jeff J. sent me these photos he took of the Space Shuttle Atlantis' final landing at Cape Canaveral at 5:57 a.m. EDT on July 21, 2011.
Alas, this is the final flight of the five-craft Space Shuttle program, which commenced on 12 April, 1981 and totaled 135 missions (Columbia and Challenger were lost). America has no replacement system in the queue. Prior to the shuttle fleet, the Apollo series ran from February 21, 1967 with Apollo 1 (a fire killed the crew on the launch pad) through the splashdown of Apollo 17 on December 19, 1972. We landed two men on the moon at the Sea of Tranquility with Apollo 11 on July 20, 1969. At least during that 9-year void of manned space flight, there was a replacement vehicle in the works (delayed from March 1978). Now, we have no national <more>
Some noted thinkers and problem solvers claim higher education helps foster "out-the-box" thinking. This might just be a prime example. Here is my solution to the need for tiebacks to go with the new bedroom curtains. While attending the IMS2011 show in Baltimore, Melanie and I each were treated to neck straps for holding ID cards. EM simulation software vendor CST provided them as part of their promotion campaign. The bright color scheme matches these curtains perfectly, and the straps happen to be just about the right size for the task at hand. There is only one window in the room, so two straps are enough. In case your fashion sensibility is concerned that using the CST neck straps would possibly cheapen the decor, fear not. The curtains are straight off the Walmart rack. No harm done. Until such time as the bedroom gets painted and remodeled, CST gets some free advertising from the neck straps.
this cool or what? You might be tempted to suspect Photoshopping, but supposedly this image of lightning striking
the Eiffel Tower is legit. "Snapper Bertrand Kulik took the split second snap as bad weather swept in over the French
capital. It shows the very moment a giant fork of lightning struck the popular tourist attraction. It was taken
in July last year but has only just emerged after it was published in a French magazine." To me, it appears the
lightning bolt is actually behind the tower, not propagating through it. The nav hazard light at the top and other
lights on it would likely have been instantly vaporized due to the current spike and resulting potentials built
up throughout the structure. With as good of a conductor and as good of a ground as the Eiffel Tower presents, the
coronal discharge would have ceased near the highest point of the strike, since after that there is not a high enough
concentration of charge and heat to vaporize the surrounding atmosphere. Do a search on
lightning rod strikes and you will see what I mean.
This picture showed up in Scientific American as their monthly "the big picture" feature. It is a 6-meter diameter sphere covered by more than 10 million OLEDs. The orb hangs in the National Museum of Emerging Science and Innovation, in Tokyo. 10,362 panels, each measuring 96 x 96 mm and containing a 16 x 16 OLED array, are wired into a giant programmable array that can represent the normal color spectrum. Its most obvious use is as a projector of Earth, but it can do the moon or any planet (Saturn and Uranus w/o rings, of course, although ring shadows could be accommodated); however, any spherical object could be represented. For that matter, conformal mapping techniques could render non-round images from certain perspectives. Of course, the globe is really a gigantic advertisement for Mitsubishi OLED large-screen televisions, which is OK by me. OLED displays have a much faster pixel refresh rate then any other display type, and do not need backlighting. Their main weakness at this point is lifetime, which is about 14,000 hours to half the original brightness. Driver circuits can compensate a little by upping current, but then the efficiency suffers. Like everything else, things will get better.
When a structure is measured for an official height, it includes every part of the structure - including the antenna(s) and support mast(s) that is(are) almost always included at the very top. Take the current height record holder, the Burj Khalifa, in Dubai, for instance. The overall height of the structure including the antenna is 828 m; however, the antenna is 207 m tall, so the building itself is only 621 m. As can be seen from the chart below, only two pure antennas (including support mast) are included in the world's tallest structures. Those antennas are used for television, radio, data, and even optical transmission.
If you read Arthur C. Clarke's article in the October 1954 edition of Wireless World where he conceived of a geosynchronous satellite system to broadcast television signals rather than using a series of terrestrial towers, it is apparent why even using antennas at heights like the one on the Burj Khalifa would not even come close to providing coverage needed for the entire earth. The following table gives the line-of-sight, including earth <more>
was split by a court in 1984 because it was deemed a monopoly. It was the era of the "Baby Bells"
(Regional Bell Operating Companies), which are: Ameritech
(acquired by SBC in 1999, now AT&T), BellSouth
(acquired by AT&T in 2006), Pacific Telesis (acquired by SBC in 1997, now
AT&T), Southwestern Bell (name changed to SBC Communications in 1995; then
AT&T in 2005), Bell Atlantic (name changed to Verizon in 2000 after acquiring
GTE), NYNEX (acquired by Bell Atlantic in 1997, now Verizon), and U S WEST
(acquired by Qwest in 2000; acquired by CenturyLink in 2011), . Got all that?
Note the first four are AT&T again, two are now Verizon, and then there's Century Link
(who?). So much for breaking up the monopoly. In the news now is an attempt by
AT&T to buy T-Mobile, a telecom company owned by Germany's Deutsche Telekom AG. The handy chart above maps out
the evolution, just in case you lost track years ago. If you have been wondering why your phone service has been
continuing to get better with the dawning of each new day, maybe this helps explain it.
Here is yet another reason you probably don't want the government in charge of your health care. A few weeks ago, I read a story about a new "Department of Innovation" that was being established by the Smithsonian Institute. The site is more of an aggregation of high-tech news than a think tank. When I originally went to the DoI's website, the first thing that struck me was the logo. Note the mutual intermeshing of gears - anything look strange about it to you? Yep, they are inextricably locked so that no motion is possible (aside from the slop between the cogs). It was not long before the image began making headlines all over the Internet. A few days ago when I visited the DoI website, the logo had not been changed, but this morning I saw that the two smaller gears no longer intermesh. They probably convened a committee, held meetings at a posh hotel in Hawaii, formed a consensus, and decided to pay a minority consultant a couple hundred thousand dollars to recommend a new design. Note that even the Rev B logo's gears still have an uneven gap between the cog ends and the adjacent gear - something any modern, CAD-designed gear set would not exhibit. A new committee will deal with that.
You've heard of rad-hardened electronics. Meet round-hardened electronics. This notebook computer belongs to a U.S. soldier stationed in Afghanistan. Fortunately for him, he had it in a backpack when he found himself under sniper fire. Two bullets hit him in the shoulder. Six more were stopped by this HP notebook computer. You can bet that at least one of those six would have hit a major organ and caused critical injuries. My HP warranty does not cover acts of war or acts of God, but the good folks at HP replaced the soldier's computer and even let him keep the shot-up one as a souvenir. There have been other instances of computers stopping bullets in a combat zone as far back as in the early 1990s during the first Gulf War. I will have to be sure to carry my HP laptop with me in places where I can't carry my Ruger 380 LCP.