Author: Jenny List

3282 Articles

It’s Not A Computer If It Doesn’t Have A Cartridge Slot

March 13, 2021 by 25 Comments

For viewers of sci-fi TV and films from the 1960s onwards, the miniaturisation of computer hardware has been something of a disappointment. Yes, it’s amazing that we can get 1.21 Jigabytes onto a memory card that fits comfortably under a postage stamp, but we were promised a different future. One of satisfyingly chunky data modules that activated everything from starships to handheld data recorders to malevolent rogue supercomputers, and one that has so far only materialised in the form of cartridges for game consoles.

Our colleague [Tom Nardi] has the solution for his cyberdeck though, in the form of 3D-printed cartridge shells that hide regular USB hardware and mate with a concealed USB socket in the slot. So far he’s designed cartridges for Flash drives, WiFi and Bluetooth adapters, a Wemos D1 Mini, a receptacle, and a parametric reference design.

It’s a bit of pleasing retro fun, but behind it all could be a surprisingly practical and useful expansion system. Each cartridge contains enough space for a lot of extra electronics, so it’s almost the ideal format for building a USB-driven project inside. Best of all since the interface is USB, it still works with conventional USB plugs and sockets. We like the idea, and it’s one that would be a good addition to any cyberdeck project.

We’re far more used to seeing home-made cartridges on game consoles.

Continue reading “It’s Not A Computer If It Doesn’t Have A Cartridge Slot” →

Time’s Almost Up For The FrankenFMs: The Impending Switchoff Of Analog TV

March 13, 2021 by 30 Comments

In a time when multi-channel digital TV is the norm it’s a surprise to find that a few low-power analog stations are still clinging on in some American cities. These are sometimes fill-in stations for weak signal areas, or more usually the so-called “FrankenFM” stations who transmit static images or digital patterns and derive income from their sound channel lying at the bottom end of the FM band to form unintended radio stations. Their days are numbered though, because the FCC is requiring that they be turned off by July 13th. There’s a way forward for the broadcasters to upgrade to low-power digital, but as you might expect they’re more interested in retaining the FrankenFM frequency from which they derive income.

The industry is represented by the LPTV coalition, who have requested permission to retain their FM frequency alongside their digital service. This has faced stiff opposition from other broadcasters, who see the very existence of the FrankenFM stations as a flagrant flouting of the rules that shouldn’t be rewarded. The FCC have yet to make a ruling, so there remains a slim chance that they may win a reprieve.

The sad tale of the few lingering analog TV stations in the USA is a last flickering ember of a once-huge industry that has been eclipsed without anyone but a few vintage technology geeks noticing, such has been the success of digital broadcasting. But analog TV is a fascinating and surprisingly intricate system whose passing however faint is worth marking.

Header: Tiia Monto, CC BY-SA 3.0.

RIP Lou Ottens, Developer Of The Compact Cassette And More

March 12, 2021 by 30 Comments

It’s with sadness that we note the passing at the age of 94 of the long-time Phillips engineer Lou Ottens, who is best known as the originator of the Compact Cassette audio tape format that was so ubiquitous through the later decades of the 20th century. Whether you remember cassettes as the format for 8-bit software, for teenage mixtapes on a Walkman, they began life at his hands in the early 1960s at the Phillips factory in Hasselt, Belgium.

Through a long career with the Dutch electronics company, he was responsible either directly or in part for a string of consumer electronic devices that we would see as ubiquitous over the latter half of the century. Before the cassette he had developed the company’s first portable reel-to-reel tape recorder, and in the 1970s while technical director of their audio division he led the team that would develop the CD. He was reported as saying that his great regret was not beating Sony to the development of the miniature cassette player that would be sold as the Walkman, but we’d suggest that the Walkman would not have been possible without the cassette in the first place.

So next time you handle a cassette tape, spare a thought for Lou, an audio engineer whose work permeated so much of the last half-century.

Thanks [Carl] for the tip.

Images: Lou Ottens by Jordi Huisman CC BY-SA 4.0 and “An early Phillips cassette recorder” by mib18 CC BY-SA 3.0

 

Our Curious Relationship With Caffeine

March 10, 2021 by 109 Comments

If you were to paint a few stereotypes surrounding our community, where would you start? Maybe in apparel habits: the t-shirt from a tech conference, or the ubiquitous hoodie. Or how about leisure pursuits: gaming, or even D&D? There’s one thing I can think of that unites most of us, we have a curious affinity for caffeine. Is it a propensity for working into the dark of the night that’s responsible, or perhaps those of us with ADHD find the alertness helpful, but whatever it is we like our coffee and energy drinks. Rare is the hackerspace without a coffee machine and a fridge full of energy drinks, and I have lost count of the times I have been derided by the coffee cognoscenti among my peers for my being satisfied with a mug of mere instant. Deprived of my usual socialisation over the festive period by the pandemic, and contemplating my last bottle of Club-Mate as I drank it, I took a while to ponder on our relationship with this chemical.

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Full DIY: A UNIX Clone On TTL

March 9, 2021 by 27 Comments

Making a CPU or indeed a whole computer system from scratch using discrete logic chips is by no means an unusual project, but it’s still one that requires quite a lot of technical ability and understanding of how computers work. Similarly, writing a UNIX-like operating system from scratch is something that’s been done more than once, but which definitely puts the author in an exclusive breed.  Creating a CPU and computer system from discrete logic and then writing a UNIX-like OS for it? That’s definitely something new, but here’s [RobotMan2412] with both CPU and operating system to prove it!

The GR8CPU as he calls it is an 8-bit design with a 16-bit address space, making it equivalent to a typical mid-to-late 1970s 8-bit chip. He’s on revision 3 of the processor, and even makes the bold suggestion that it might be the most complex breadboard CPU ever made. That’s impressive enough, but to add a UNIX-like operating system makes it special.

While he has a real GR8CPU, it appears he’s also written an emulator with access to a disk filesystem, and it’s on this that he shows us the OS running. Don’t expect an all-singing all-dancing desktop OS here, instead it’s a kernel and very basic command line that’s just about able to run a Hello World. The kernel is hand-coded in assembler and is about 5 kB in size.

We look forward to seeing more of this project, and hope maybe he’ll one day soon publish the source. As a reminder that this is a perfectly capable platform for the job, here’s the original UNIX running on a vintage DEC PDP7.

What Can A $30 USB Spectrum Analyser Do For Me?

March 8, 2021 by 36 Comments

As mildly exotic silicon has become cheaper and the ingenuity of hardware hackers has been unleashed upon it, it’s inevitable that some once-unattainably expensive instruments will appear as cheap modules from China. The LTDZ spectrum analyser on the bench today covers 35 MHz to 4.4 GHz, and has a USB interface and tracking source. It has been available from all the usual outlets for a while now either as a bare PCB or in a metal box about the size of a pack of cards.

We’ve already taken a look at the $50 VNA, and this time it’s the turn of the $30 spectrum analyser, in the form of a little device that I succumbed to while browsing Banggood.

I ordered one, along with an attenuator and RF bridge for SWR measurements, and after the usual wait for postage my anonymous grey package arrived and it was time to give it a look and consider its usefulness. It’s a design derived from one published in Germany’s Funkamateur (“amateur radio”) magazine early in the last decade, and unscrewing the end plate to slide out the board from its extruded enclosure we can see what makes it tick. Continue reading “What Can A $30 USB Spectrum Analyser Do For Me?” →

A Tiny Tube Amp For Not A Lot

March 7, 2021 by 49 Comments

At the extreme budget end of tube audio lie single-tube amplifiers usually using very cheap small-signal pentodes. They’ve appeared here before in various guises, and a fitting addition to those previous projects comes from [Kris Slyka]. It’s a classic circuit with a transformer output, and it provides enough amplification to drive a pair of headphones or even a speaker at low levels.

The fairly conventional circuit of the tube amplifier.

Most tube enthusiasts will instantly recognize the anode follower circuit with a transformer in the anode feed through which the output is taken. The tube works in Class A, which means that it’s in its least efficient mode but the one with the least distortion. The transformer itself isn’t an audio part, but a small mains transformer taken from a scrap wall wart. It serves not only for isolation, but also to transform the high impedance output from the tube into a low impedance suitable for driving a headphone or speaker.

The HT voltage is a relatively low 24 V, but it still manages to drive headphones acceptably. Speaker levels require a pre-amp, but even then it’s likely that this circuit is pushing the tube beyond what it’s capable of with a speaker. The more it operates towards the edge of its performance envelope the more distortion it will generate and the worse a sound it will produce. This isn’t such a problem in a guitar application as here, but hi-fi enthusiasts may find it to be too much. It would be interesting to subject it as a headphone amplifier to a series of audio tests to evaluate the effect of a mains transformer over a dedicated audio one.

Last year we took a very in-depth look at the commonly-available Chinese kit pre-amps that use a similar anode-follower circuit but without the transformer. We’ve also seen a similar amp that uses an op-amp as an impedance converter, as well as a novel take on the idea whose unusual biasing allows it to run from only 3.3 volts. These circuits can be so cheap to get started with that we’d suggest anyone give them a try.