Author: Al Williams

4504 Articles

Next Floor: Geosynchronous Satellites, Orbiting Laboratories

August 3, 2022 by 40 Comments

On Star Trek, if you want to go from one deck to another, you enter a “turbolift” and tell it where you want to go. However, many people have speculated that one day you’ll ride an elevator to orbit instead of using a relatively crude rocket. The idea is simple. If you had a tether anchored on the Earth with the other end connected to a satellite, you could simply move up and down the tether. Sound simple, so what’s the problem? The tether has to withstand enormous forces, and we don’t know how to make anything practical that could survive it. However, a team at the International Space Elevator Consortium could have the answer: graphene ribbons.

The concept is not new, but the hope of any practical material able to hold up to the strain has been scant. [Arthur C. Clarke] summed it up in 1979:

How close are we to achieving this with known materials? Not very. The best steel wire could manage only a miserable 31 mi (50 km) or so of vertical suspension before it snapped under its own weight. The trouble with metals is that, though they are strong, they are also heavy; we want something that is both strong and light. This suggests that we should look at modern synthetic and composite materials. Kevlar… for example, could sustain a vertical length of 124 mi (200 km) before snapping – impressive, but still totally inadequate compared with the 3,100 (5,000 km) needed.

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Ham Radio Hacking: Thinking Inside The Box

August 2, 2022 by 19 Comments

There are two ways to deal with improving ham radio receivers, or — for that matter — any sort of receiver. You can filter and modify the radio frequency including the radio’s intermediate frequency, or you can alter the audio frequency output. Historically, RF and IF techniques have been the most valued because rejecting unwanted noise and signals early allows the rest of the radio to focus on the actual signal of interest. However, audio filters are much easier to work with and until recently, DSPs that could handle RF frequencies were expensive and uncommon. However, [watersstanton] shows us how to make what could be the cheapest audio enhancer ever. It is little more than a modified cardboard box, and you can see and hear the result in the video below.

On the one hand, you shouldn’t expect miracles. On the other hand, you probably have box laying around and can try it in the next three minutes so why not give it a go? You can hear a bit of difference when using the box and not using the box.

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Never Too Rich Or Thin: Compress Sqlite 80%

August 1, 2022 by 11 Comments

We are big fans of using SQLite for anything of even moderate complexity where you might otherwise use a file. The advantages are numerous, but sometimes you want to be lean on file storage. [Phiresky] has a great answer to that: the sqlite-zstd extension offers transparent row-level compression for SQLite.

There are other options, of course, but as the post mentions, each of these have some drawbacks. However, by compressing each row of a table, you can retain random access without some of the drawbacks of other methods.

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When [Carl] Says Jump, PCBs Say “How High?”

July 30, 2022 by 4 Comments

We’ve noticed that [Carl Bugeja] likes flexible PCBs. His latest exploit is to make PCB-based springs that combine with some magnets to create little devices that jump. We aren’t sure what practical use these might have, but they are undeniably novel and you can see them — um — jumping around, in the video, below.

[Carl] did many experiments with the spring construction and design. You can see several of the iterations in the video, not all of which worked out well. A PCB coil in the base becomes magnetized when current flows and this repels or attracts the magnets at the other end of the spring. What can you do with a PCB spring? We aren’t sure. Maybe this is how your next microrobot could climb stairs?

Adding stiffeners produced springs too stiff for the electromagnet to attract. We wondered if a different coil design at the base might be more effective. For that matter, you might not have to use a flat PCB coil in that position if you were really wanting to optimize the jumping behavior.

Usually, when we are checking in with [Carl] he is making PCB-based motors. Or, sometimes, he’s making PCB heaters for reflow soldering. We’ve seen jumping robots, before, of course. we will say the magnets seem less intense than using compressed air.

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Testing Antennas With WSPR

July 29, 2022 by 20 Comments

There are many ways to test HF antennas ranging from simulation to various antenna analyzers and bridges. However, nothing can replace simply using the antenna to see how it works. Just as — supposedly — the bumblebee can’t fly, but it does so anyway, it is possible to load up some bed springs and make contacts. But it used to be difficult — although fun — to gather a lot of empirical data about antenna performance. Now you can do it all with WSPR and [TechMinds] suggests a moderately-priced dedicated WSPR transmitter to do the job. You can see a video about the results of this technique below.

While WSPR is often cited as taking the fun out of ham radio, it is perfect for this application. Connect the transmitter and a few hours later, visit a web page and find out where you’ve been heard by an objective observer. If you had a few of these, you could even examine several antennas at similar times and conditions.

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Calculus Made Easy In The Car

July 29, 2022 by 24 Comments

If you had the traditional engineering education, you’ve made your peace with calculus. If you haven’t, you may have learned it on your own, but for many people, calculus has a reputation for being super difficult. While some of the details can be very tricky, the core concepts are actually simple and [Mathologer] has a very simple explanation along with some good graphics that can help you get started on calculus mastery if you’ve been putting it off. Using a car on the highway as the prototypical example, he covers quite a bit of ground in the 30 minute video that you can see below.

Of course, this isn’t a unique idea that calculus is actually simple. The video credits the great book “Calculus Made Easy” that we’ve talked about before. That 100-year-old (and then some) book has a similar approach to the topic.

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Go Big Or Go Home: 0.6 Mm Nozzles Are The Future

July 29, 2022 by 51 Comments

Most desktop fused deposition modeling (FDM) 3D printers these days use a 0.4 mm nozzle. While many people have tried smaller nozzles to get finer detail and much larger nozzles to get faster printing speed, most people stick with the stock value as a good trade-off between the two. That’s the conventional wisdom, anyway. However, [Thomas Sanladerer] asserts that with modern slicers, the 0.4 mm nozzle isn’t the best choice and recommends you move up to 0.6 mm.

If you know [Thomas], you know he wouldn’t make a claim like that without doing his homework. He backs it up with testing, and you can see his thoughts on the subject and the test results in the video below. The entire thing hinges on the Ultimaker-developed Arachne perimeter generator that’s currently available in the alpha version of PrusaSlicer.

We’ve experimented with nozzles as small as 0.1 mm and, honestly, it still looks like an FDM 3D print and printing takes forever at that size. But these days, if we really care about the detail we are probably going to print with resin, anyway.

There are a few slicer settings to consider and you can see the whole setup in the video. The part where an SLA test part is printed with both nozzles is particularly telling. This is something that probably shouldn’t print well with an FDM at all. Both nozzles had problems but in different areas.

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