A Basic Guide To Shielding
[GreatScott] has recently been tinkering in the world of radio frequency emissions, going so far as to put their own designs in a proper test chamber to determine whether they meet contemporary standards for noise output. This led them to explore the concept of shielding, and how a bit of well-placed metal can make all the difference in this regard.
The video focuses on three common types of shielding—absorber sheets, shielding tapes, and shielding cabinets. A wide variety of electronic devices use one or more of these types of shielding. [GreatScott] shows off their basic effectiveness by putting various types of shielding in between a noise source and a near-field probe hooked up to a receiver. Just placing a bit of conductive material in between the two can cut down on noise significantly. Then, a software defined radio (SDR) was busted out for some more serious analysis. [GreatScott] shows how Faraday cages (or simple shielding cabinets] can be used to crush down spurious RF outputs to almost nothing, and how his noisy buck-boost designs can be quieted down with the use of the right absorber sheets that deal well with the problematic frequencies in question. The ultimate upshot of the tests is that higher frequencies respond best to conductive shielding that is well enclosed, while lower frequency noise benefits from more absorptive shielding materials with the right permeability for the job.
Shielding design can be a complex topic that you probably won’t master in a ten minute YouTube video, but this content is a great primer if you’re new to the topic. We’ve covered the topic before, too, particularly on how a bit of DIY shielding can really aid a cheap SDR’s performance. Video after the break.
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A Computer That Fits Inside A Camera Lens
For a long while, digital single-lens reflex (DSLR) cameras were the king of the castle for professional and amateur photography. They brought large sensors, interchangeable lenses, and professional-level viewfinders to the digital world at approachable prices, and then cemented their lead when they started being used to create video as well. They’re experiencing a bit of a decline now, though, as mirrorless cameras start to dominate, and with that comes some unique opportunities. To attach a lens meant for a DSLR to a mirrorless camera, an adapter housing must be used, and [Ancient] found a way to squeeze a computer and a programmable aperture into this tiny space.
The programmable aperture is based on an LCD screen from an old cell phone. LCD screens are generally transparent until their pixels are switched, and in most uses as displays a backer is put in place so someone can make out what is on the screen. [Ancient] is removing this backer, though, allowing the LCD to be completely transparent when switched off. The screen is placed inside this lens adapter housing in the middle of a PCB where a small computer is also placed. The computer controls the LCD via a set of buttons on the outside of the housing, allowing the photographer to use this screen as a programmable aperture.
The LCD-as-aperture has a number of interesting uses that would be impossible with a standard iris aperture. Not only can it function as a standard iris aperture, but it can do things like cycle through different areas of the image in sequence, open up arbitrary parts or close off others, and a number of other unique options. It’s worth checking out the video below, as [Ancient] demonstrates many of these effects towards the end. We’ve seen some of these effects before, although those were in lenses that were mechanically controlled instead.
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Thanks to [kemfic] for the tip!
Retrotechtacular: Mr. Wizard Jams with IBM
You may not remember [Mr. Wizard], but he was a staple of nerd kids over a few decades, teaching science to kids via the magic of television. The Computer History Archives Project has a partially restored film of [Mr. Wizard] showing off sounds and noise on a state-of-the-art (for 1963) Tektronix 504 oscilloscope. He talks about noise and also shows the famous IBM mainframe rendition of the song “Daisy Bell.” You can see the video along with some extras below.
You might recall that the movie “2001: A Space Odyssey” paid homage to the IBM computer’s singing debut by having HAL 9000 sing the same song as it is being deactivated. The idea that HAL was IBM “minus one” has been repeatedly denied, but we still remain convinced.
Can you imagine a TV show these days that would teach kids about signal-to-noise ratio or even show them an actual oscilloscope? We suppose that’s what YouTube is for.
At about the 17-minute mark, you can see some enormous walkie-talkies. A far cry from today’s cell phones. At the 27-minute mark, another film shows how engineers at Bell created the song using a mainframe.
We wish there were a modern version of [Mr. Wizard]. Then again, there’s no reason you can’t fill in. You might not be on TV, but you can always drop in on a few classrooms.
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