Your RF Cafe
This collection of video and a few audio files represents files that have been featured on the RF Cafe homepage. Every week or so a new file is added that should be of interest to RF Cafe visitors.
Please send me an e-mail if you have a good subject. Note: "Videos for Engineers" formerly went by the name "Cool Videos."
visitor Paul A. sent me a link to this video of a rotary spark gap transmitter that was on display a
the 2010 Dayton Hamvention. The hand-crafted replica is a work of art. Jim Stafford, W4QO, provided
the demonstration during the Early History of Ham Radio Forum. "A spark-gap transmitter is a device
for generating radio frequency electromagnetic waves using a spark gap. These devices served as the
transmitters for most wireless telegraphy systems for the first three decades of radio (1887–1916) and
the first demonstrations of practical radio were carried out using them. In later years
(prior to the development of practical vacuum tube systems) somewhat
more efficient transmitters were developed based on high-speed Alexanderson alternators and Poulsen
Arc generators, but spark transmitters were still preferred by most operators."
Near Field Communications (NFC) is still a fairly fledgling technology in term of adoption its capabilities. On nearly a daily basis, I search tech websites for news that includes noteworthy articles on NFC. One such website is NFC World, which is where I found this item. In it, two students from Stanford University's MobiSocial project give a live presentation of the way near field communications can be used to adapt appropriately equipped appliances for use. Linking of devices is accomplished by placing two or more within the coupling range of the NFC coils (using magnetic induction between loop antennas), then software allows communications between, and manipulation of the devices. NFC operates at 13.56 MHz, with data rates from 106 kbit/s to 848 kbit/s. There are already many commercial applications that have already adopted NFC, including ticketing, vending machine payment, P2P software apps, and even some personal identity cards.<more>
Can you be nostalgic for a time in which you never lived? When I watch these old films of production lines back in the 1930s and 1940s, it makes me long for the days of America being a manufacturing powerhouse. When I worked at the former GE plant in Syracuse, NY, I used to walk around some of the long-closed buildings that at one time were a beehive of activity producing TVs, washing machines, and clock radios, and wonder what it would have been like.
This video titled Electrons on Parade was produced by RCA sometime around 1942. It is amazing how labor-intensive the process was. The automated machines are equally impressive for the precise operations performed without the benefit of microprocessor-controlled stepper motors and a nice LabView® software interface. Notice that the majority of production line workers are women who, as a class, made a move from fulltime housewives to essential workers to satisfy needs made necessary by the war effort since the men had gone off to battle against Axis powers. Rosie the Riveter was <more>
Videos of radio tower climbers are cool for sure. Fear of heights notwithstanding, the physical strength and stamina required to scale 1,000+-foot towers is more than most people could endure. Winds aloft are typically stronger and more gusty than at ground level, so the shaking of the tower would unsettle all but the most robust stomachs and inner ears. Their bravery helps assure that communications worldwide continue nearly uninterrupted. There is another cadre of aerial linemen that deserve attention - the guys who ride on helicopter skids to maintain and repair high voltage transmission lines. One of the coolest parts of the video is where the lineman uses a metal wand to draw an arc from the power line (often at 100 kV or more) in order to bring the helicopter environment to the same potential <more>
12-year-old boy genius Jason Barnett is shown here giving an integration by parts lesson on his bedroom window. Yeah, we all used to do that at 12. Jason began studying astrophysics at 3, plays classical music from memory on the piano, and had memorized pi to 200 places - forward and backward. He also plays Guitar Hero and has a girlfriend. Now in college at Indiana U. - Purdue U. where he works on Big Bang theory, Jason has been tagged at the most brilliant human ever. "When I first walked in and saw him, I thought, 'Oh my God, I'm going to school with Doogie Howser,'" said a biochemistry major classmate. I am feeling kinda insufficient right about now. Someone needs to put a stop to Jason's stellar rise because according to modern teachings, it is just not fair that Jason be so gifted when others are not - you know, the social justice thing.
MIT has long enjoyed a reputation as one of the country's top engineering school. They were one of the first to make videos of undergraduate classroom instruction sessions available at no cost to the public (nothing is free - the tuition payers picked up the tab) through OpenCourseWare. For the past few years, hundreds of videos have been produced and posted that demonstrate various fundamental physical processes. One cool video shows how a Faraday cage keeps an electric field outside the enclosure from affecting the field inside the enclosure where, in this case E=0, and vice versa. A Van de Graaff generator supplies the electric field while a Ben Franklin doll with strands of metal tinsel attached is used as the UUT (the store must have been sold out of Michael Faraday and Robert Van de Graaff dolls). We exploit the same principle in the form of folded sheet metal shields on PCBs all the time to keep RF energy from interfering with other circuitry in the vicinity. Then, entire assemblies are shielded to prevent energy from being radiated to the outside world, as well as to keep outside world energy from influencing the performance of our circuits.<more>
Maurits Cornelis Escher, aka
M.C. Escher (1898 – 1972), was
a Dutch graphic artist known for his often mathematically inspired woodcuts, lithographs, and mezzotints.
These feature impossible constructions, explorations of infinity, architecture, and tessellations. If
you do a search on Escher's waterfall, you will find a lot of information that explains how his methods
tricked the human brain to perceive something that is not what it appears to be. There are videos, physical
models, computer models, paintings, drawings, and written theses. Even knowing that the image does not
comport with real-life experience, figuring out exactly how the spoof is executed can be difficult -
if not impossible (to some). In this video, a resourceful young man uses a physical model with a carefully
The extents to which companies have to go in order to make memorable advertisements just keeps increasing. Production costs are high, and there is no guarantee that even the most sophisticated effort will be rewarded with even close to a viral status. Judging by the very wide coverage of NTT (Nippon Telegraph and Telephone Corporation ) DoCoMo's (Do Communication over Mobile) Touch Wood SH-08C video, they seems to have a winner. You need to watch the video to appreciate planning that went into the making. Both pitch and tempo are carefully reproduced throughout. For those not familiar with classical music, the tune is Bach's "Jesu, Joy of Man's Desiring." Morihiro Harano, of Drill Inc., was the video's creator. Unfortunately, most DoCoMo phones only work with Japan's proprietary cell network, so you cannot get one for use elsewhere. Some dope posted, "Anybody else feel slightly betrayed when it turned <more>
Animals are used quite effectively in many advertising formats - the infamous yearly Super Bowl collection is replete with them. In this video, Samsung has enlisted the aid of Welsh sheepherders to help promote their line of high efficiency LEDs. It was released in advance of its 2009 debut of LED televisions. Two flocks of sheep - one black and one white - are each fitted with a battery-powered blanket of hundreds of LEDs. The skilled shepherds and amazingly competent sheep dogs then use a highly choreographed script to coax the sheep into mosaic forms that build pictures. One feat is an animated (literally) sheep form that collectively walks across the hillside. When the sun goes down, the LEDs are powered up and the sheep, among other things, emulated a game of the old Atari Pong video game. The coup de grâce is a mosaic of the Mona Lisa. Not baaaaaad!
3/8/2011Every once in a while someone upsets our comfortable existence by pointing out inconvenient realities like the problem of what happens to our electronics devices after the manufacturers convince us that we need the latest version of their wonder gadget. Unlike regular household recyclables like glass jars and cardboard cereal boxes, electronic devices contain a lot of valuable material that makes it profitable for reclamation if the work can be performed somewhere nobody really cares about the human costs of doing so. In China, India, Ghana, and many other "developing" countries, poor souls earn an existence by disassembling and performing crude processing of the components to separate heavy metals like gold, silver, lead, cadmium, beryllium, mercury, and others. For their efforts they sell their booty at a pauper's wage. <more>
As time goes by, we tend to take for granted some of the innovations in both methods and materials that changed the way business is conducted. Just as anyone under the age of 30 assumes that personal computers have always been a part of life, and anyone under 20 thinks that cell phones are issued at birth, along with a Social Security Number, even old-timers might forget that modern manufacturing techniques for mass production that we take for granted were pioneered long ago by people like Henry Ford. Not only did Mr. Ford conceive of and implement a high efficiency assembly line for his horseless carriages, but he also made a crucial decision that allowed his idea to work - he paid his employees far above the prevailing wage of the era. $5 per day (worth about $112 in 2011) was just the incentive Ford assembly line workers needed to keep up the fast paced, repetitive work (workers got to keep almost all of their pay, because there were no union dues, and Federal tax rate in 1913 was a whopping 1%). This video documents the assembly line from <more>
"Here is radio, performing swiftly and efficiently in the heat of battle," so says the narrator of RCA's promotional WWII film entitled "Radio at War." It follows brothers Joe and Jim Brown from their bedroom Ham radio set in Middletown, USA, to radio school with the Army Signal Corps and the Navy Communications Dept., respectively, and on into the field and onboard ship where they handle voice and Morse code operations. Jim is elated as he sews on his Radioman 3rd Class "crow" patch after graduating from communications school. Brother Joe departs for the battlefields of Europe as a sergeant earning "$98 per month" after his training (I earned $419/mo. as an A1C radar tech in 1979). He raves in a letter to home about the new walkie talkies that have a range up to 5 miles that will surely "play an important part after the war." Wireless communications was still in its infancy, where families gathered in front of the tube radio for news and entertainment - "The magic of radio bridging space faster than the most powerful plane."<more>