A Look At Zweikanalton Stereo Audio And Comparison With NICAM

March 19, 2023 by 1 Comment

With how we take stereo sound for granted, there was a very long period where broadcast audio and television with accompanying audio track were in mono. Over the decades, multiple standards were developed that provide a way to transmit and receive two mono tracks, as a proper stereo transmission. In a recent video, [Matt] over at [Matt’s Tech Barn] takes a look at the German Zweikanalton (also known as A2 Stereo) standard, and compares it with the NICAM standard that was used elsewhere in the world.

Zweikanalton is quite simple compared to NICAM (which we covered previously), being purely analog with a second channel transmitted alongside the first. Since it didn’t really make much of a splash outside of the German-speaking countries, equipment for it is more limited. In this video [Matt] looks at the Philips PM 5588 and Rohde & Schwarz 392, analyzing the different modulations for FM, Zweikanalton and NICAM transmissions and the basic operation of the modulator and demodulator equipment.

An interesting aspect of these modulations are the visible sidebands, and the detection of which modulation is used. Ultimately NICAM’s only disadvantage compared to Zweikanalton was the higher cost of the hardware, but with increased technological development single-chip NICAM solutions like the Philips SAA7283 (1995) began to reduce total system cost and by the early 2000s NICAM was a standard feature of TV chipsets, just in time for analog broadcast television to essentially become irrelevant.

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Hackaday Links: March 19, 2023

March 19, 2023 by 11 Comments

We get results! Well, sort of. You may recall that in this space last week we discussed Ford’s plans to exclude AM reception on the infotainment systems of certain of their cars starting in 2024. We decried the decision, not for the loss of the sweet, sweet content that AM stations tend to carry — although we always enjoyed “Traffic on the 8s” back in our dismal days of daily commuting — but rather as a safety concern, because AM radio can reach almost the entire US population with emergency information using just 75 stations. To our way of thinking, this makes AM radio critical infrastructure, and eliminating it from motor vehicles is likely to have unintended consequences. Now it seems like there’s some agreement with that position, as former administrators of FEMA (Federal Emergency Management Administration; and no, not FEDRA) have gotten together to warn about the dangers of deleting AM from cars. Manufacturers seem to be leaning into the excuse that EVs emit a lot of radio frequency interference, rendering static-sensitive AM receivers less useful than other, more profitable less susceptible modes, like digital satellite radio. That seems like a red herring to us, but then again, the most advanced infotainment option in any car we’ve ever owned is a CD player, so it’s hard for us to judge.

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The $50 Pen Plotter

March 19, 2023 by 23 Comments

[Arca] sets out to build himself a low-cost pen plotter that doesn’t require access to a 3D printer. The plotter uses a coreXY arrangement, powered by 28BYJ-48 stepper motors, which he overdrives with +12 VDC to increase the torque. Pen up and down control is done using a stepper motor salvaged from a DVD reader. The frame is constructed using PVC electrical conduit and associated fittings, and [Arca] uses the hot glue gun quite liberally. Steppers were driven by A4988 modules with heatsinks, and motion control is provided by GRBL running on an Arduino UNO.

He has a few issues with glitches on the limit switches, and is continuing to tweak the design. There is no documentation yet, but you can discern the construction easily from the video if you want to try your hand at making one of these. This is a really cool DIY plotter, and many parts you probably have laying around your parts boxes. As [Arca] says, it’s not an AxiDraw, but the results are respectable. Keep a lookout for part 2 of this project on his YouTube channel.

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The Intricacies Of Starting A Rocket Engine

March 19, 2023 by 11 Comments

Rockets are conceptually rather simple: you put the pointy bit upwards and make sure that the bit that will go flamey points downwards before starting the engine(s). Yet how to start each rocket engine type in a way that’s both safe and effective? Unlike in the Wile E. Coyote cartoons, real-life rocket engines do not have a fuse you light up before dashing off to a safe distance. Rather they use increasingly more complicated methods, which depend on the engine type and fuels used. In a recent article written by [Trevor Sesnic] with accompanying video featuring everyone’s favorite Everyday Astronaut [Tim Dodd], we’re taken through the intricacies of how flamey ends are made. Continue reading “The Intricacies Of Starting A Rocket Engine” →

3D-Printed Shredder Eats Lettuce For Breakfast

March 19, 2023 by 15 Comments

Shredding things isn’t just good for efficiently and securely disposing of them. It’s also very fun, as well. [Joonas] of [Let’s Print] didn’t have a shredder, so set about 3D printing one of their very own.

The design apes that of the big metal trash shredders you’ve probably seen in videos all over the internet. They use a pair of counter-rotating drums with big teeth. As the drums turn, the teeth grab and pull objects into the gap between the drums, where they are duly torn apart into smaller pieces.

In this design, plastic drums are pressed into service as [Joonas] does not have a metal 3D printer. A brushed DC motor is used to drive the shredder. A large multi-stage gearbox is used to step down the motor’s output and provide plenty of torque to do the job.

The shredder gets tested with plenty of amusing garbage. Everything from old vegetables, to paper, and rock-hard old cheeseburgers are put through the machine. It does an able job in all cases, though obviously the plastic drums can’t handle the same kind of jobs as a proper metal shredder. Harder plastics and aluminium cans stall out the shredder, though. The gearbox also tends to strip gears on the tougher stuff. The basic theory is sound, but some upgrades could really make this thing shine.

Is it a device that will see a lot of practical use? Perhaps not. Is it a fun device that would be the star of your next hackerspace Show and Tell? Absolutely. Plus it might be a great way to get rid of lots of those unfinished projects that always clog up your storage areas, too! Video after the break.

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Customizing The Start-Up Chime On A 1999 G3 IMac

March 19, 2023 by 3 Comments

The start-up chime on Macs is probably as recognizable as the default Nokia ringtone in this day and age. Yet much like a ringtone, so too one might want to change the start-up chime on a Mac. This is something which [Doug Brown] has done in the past already on a Power Mac G3 in 2012, which made him instantly an expert on the topic in the eyes of a reader who wanted to know how to change the chime on a 1999 iMac. While the firmware on both these systems is written in Forth, it did take a bit of sleuthing to figure out where the chime was hiding in the firmware image, and how to change it.

The target iMac is somewhat unique in that it has a G4 PPC CPU rather than the more common G3. The firmware is similar enough that it was a snap to simply search the newer iMac’s firmware for the signature of the chime sound data. This turned out to be the identical QuickTime IMA ADPCM format-encoded data, yet what was different was how this data was integrated into the firmware image. Key is finding the area in the firmware where not only the address of the chime data’s start is defined, but also its length. Finally, the checksums in the firmware image have to be updated so that it matches the patched data.

Reverse-engineering the checksum calculation in the Forth code turned out to be fairly straightforward, but getting the new firmware on the iMac turned out to be the biggest struggle, as [Doug] didn’t want to inflict running a manual firmware update onto this reader he was doing all this work for. This led [Doug] to do some more reverse-engineering using Ghidra to enable the use of the automatic updater like a regular firmware update.

In the end it all worked out great, and now another iMac no longer has the Mac chime on start-up.

Tiny PCB PiezoPiano Plays Just One Octave

March 19, 2023 by 11 Comments

Grand pianos are beautiful instruments, but take up altogether too much space. Upright pianos are smaller, but still fairly hefty. When it comes to the PiezoPiano, though, we suspect nobody could complain about its diminutive size. It’s a tiny thing with just one buzzy little octave for your playing pleasure.

The PiezoPiano is a single PCB device with a ATmega4809 running the show. It has eight buttons and eight piezo transducers that give you just one octave’s range on the keyboard. Truth be told, that’s only in one scale; you’re not getting the whole twelve tones of flats and sharps included. And, when we say keyboard, we really mean “tactile buttons.” You get the drift. It’s all assembled in a cute enclosure mimicking the shape of a real grand piano.

Fundamentally, it’s a cute little musical desktoy that reminds us greatly of the Stylophone. Impressively, though, those eight buzzers mean it has eight-note polyphony. That’s nothing to sniff at compared to all the monophonic synths out there. It’s also available on Tindie if you’d like to buy a kit off the shelf. Video after the break.

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