Modern Radio Receiver Architecture: From Regenerative To Direct Conversion

July 17, 2020 by Al Williams 5 Comments

Modern radio receivers have a distinct advantage over the common early designs which I covered in my previous article. Most of the receivers you will have worked with over the past couple decades are designs by Edwin Armstrong; regenerative, superregenerative, or most commonly superheterodyne. These are distinguished by a few fascinating key traits that bring both benefits and drawbacks.

Today let’s dive into Mr. Armstrong’s receivers. I’ll also talk about DC receivers which, despite the name, are not made to listen to batteries. These are receivers you are much more likely to encounter in modern equipment.

Regenerative and Superregenerative

The regenerative receiver is all about doing more with less. You still see some of these in simple applications like RF remote controls. The idea derives from how an oscillator works. In a simple way of thinking, an oscillator is an amplifier with enough positive feedback that any tiny signal at the right frequency will amplify and then, through feedback, continue to output over and over. If everything were perfect, then, an oscillator would have infinite gain at a given frequency.

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Hackaday Podcast 076: Grinding Compression Screws, Scratching PCBs, And Melting Foam

July 17, 2020 by Mike Szczys 3 Comments

Hackaday editors Elliot Williams and Mike Szczys are enamored by this week’s fabrication hacks. There’s a PCB mill that isolates traces by scratching rather than cutting. You won’t believe how awesome this angle-cutter jig is at creating tapered augers for injection molding/extruding plastic. And you may not need an interactive way to cut foam, but the art from the cut pieces is more than a mere shadow of excellence. Plus we gab about a clever rotary encoder circuit, which IDE is the least frustrating, and the go-to tools for hard drive recovery.

Take a look at the links below if you want to follow along, and as always, tell us what you think about this episode in the comments!

Direct download (60 MB or so.)

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This Week In Security: Twitter, Windows DNS, SAP RECON

July 17, 2020 by Jonathan Bennett 8 Comments

Twitter just had their biggest security breach in years. Mike warned us about it on Wednesday, but it’s worth revisiting a few of the details. The story is still developing, but it appears that malicious actors used social engineering to access an internal Twitter dashboard. This dashboard, among other interesting things, allows directly changing the email address associated with an account. Once the address is changed to the attacker’s, it’s simple to do a password reset and gain access.

The bitcoin address used in the crypto scam ended up receiving nearly $120,000 USD worth of bitcoin, all of which has been shuffled off into different accounts. It’s an old and simple scam, but was apparently rather believable because the messages were posted by verified Twitter accounts.

A series of screenshots have been posted, claiming to be the internal Twitter dashboard used in the attack. More than a few eyebrows have been raised, as a result of that dashboard. First off, the fact that Twitter employees can directly change an account’s email address is asking for trouble. Even more interesting are the tags that can be added to an account. “Trends Blacklist” and “Search Blacklist” do call to mind the rumors of shadow-banning, but at this point it’s impossible to know the details. Motherboard is reporting that Twitter is removing that screenshot across the board when it’s posted, and even suspending accounts that post it. Of course, they’d do that if it were faked as well, so who knows? Continue reading “This Week In Security: Twitter, Windows DNS, SAP RECON” →

Hyundai Makes Push Towards Fuel Cell Trucking

July 16, 2020 by Lewin Day 102 Comments

Hyundai has begun shipping fuel-cell based heavy duty trucks to face off against battery-electric trucks in the commercial hauling market.

Battery electric vehicles, more commonly known as electric cars, have finally begun to take on the world in real numbers. However, they’re not the only game in town when it comes to green transportation. Fuel cells that use tanks of hydrogen to generate electricity with H₂O as the main byproduct have long promised to take the pollution out of getting around, without the frustrating charge times. Thus far though, they’ve failed to make a major impact. Hyundai still think there’s value in the idea, however, and have developed their XCIENT Fuel Cell truck to further the cause. Continue reading “Hyundai Makes Push Towards Fuel Cell Trucking” →

Printed It: Print-in-Place PCB Gripper

July 15, 2020 by Tom Nardi 10 Comments

The goal of Printed It is to showcase creations that truly embrace the possibilities offered by desktop 3D printing. The most obvious examples are designs that can be printed quickly and cheaply enough that they’re a valid alternative to commercially available products. But as previous entries into the series have shown, there are also technical considerations. Is it simply a duplicate of something that could be produced via traditional means, or does the design really benefit from the unique nature of 3D printing?

A perfect example is the Print-in-Place PCB Holder/Gripper created by SunShine. This design is able to hold onto PCBs (or really, whatever you wish) without any additional components. Just pull it off the bed, and put it to work. While having to add a rubber band or generic spring would hardly be an inconvenience, there’s always something to be said for a design that’s truly 100% printable.

The secret is the dual flat spiral springs integrated into the device’s jaws. While most of the common thermoplastics used in desktop 3D printing are relatively stiff, the springs have been designed in such a way that they can be printed in standard PLA. The backside of the jaws have teeth that mesh together, so the energy of the springs is combined to provide a clamping force. Serrations have been added to the jaws to catch the edge of the PCB and help stabilize it.

Visually, it’s certainly striking. The design largely eschews right angles, giving it an almost biological appearance. Many have compared it to the head of a mantis, or perhaps some piece of alien technology.

There’s no question that the design leverages the strengths of 3D printing either; there’s no other way to produce its intricate interlocking components, especially without the use of any sort of fasteners. In short, this design is an ideal candidate for Printed It. But there’s still one question to answer: does it actually work?

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Jerry Lawson And The Fairchild Channel F; Father Of The Video Game Cartridge

July 14, 2020 by Jenny List 14 Comments

The video game console is now a home entertainment hub that pulls in all forms of entertainment via an internet connection, but probably for most readers it was first experienced as an offline device that hooked up to the TV and for which new game software had to be bought as cartridges or for later models, discs. Stepping back through the history of gaming is an unbroken line to the 1970s, but which manufacturer had the first machine whose games could be purchased separately from the console? The answer is not that which first comes to mind, and the story behind its creation doesn’t contain the names you are familiar with today.

The Fairchild Channel F never managed to beat its rival, the Atari 2600, in the hearts of American youngsters so its creator Jerry Lawson isn’t a well-known figure mentioned in the same breath as Atari’s Nolan Bushnell or Apple’s two Steves, but without this now-forgotten console the history of gaming would have been considerably different.

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