Many of us will have found dusty forgotten pieces of electronics and nursed them back to health, but we were captivated by [Don]’s tale of electronic revival. Instead of perhaps a forgotten computer or television, his barn find was a Heathkit linear amplifier for radio amateurs. In that huge box underneath an impressive layer of grime were a pair of huge tubes, along with all the power supply components to give them the 2 kV they need. It should have been good for a kilowatt when new, can it be made to go on air again?
Perhaps understandably with such an old device, after cleaning away the dust of ages he replaced the power supply circuitry with new parts and PCBs. A linear amplifier is surprisingly simple, but because of the voltages and power concerned there’s a need to treat its power circuits with respect. On first power-up the filaments work and the rails come up, so when given some RF drive it comes alive. Coupled with a case restoration you’d never know how dreadful a state it had been in.
From the consumer space it often would appear as if Intel’s CPU making history is pretty much a straight line from the 4004 to the 8080, 8088 and straight into the era of Pentiums and Cores. Yet this could not be further from the truth, with Intel having churned through many alternate architectures. One of the more successful of these was the Intel i960, which is also the topic of a recent article by [Ken Shirriff].
Remarkably, the i960 as a solid RISC (Reduced Instruction Set Computer) architecture has its roots in Intel’s ill-fated extreme CISC architecture, the iAPX 432. As [Ken] describes in his comparison between the i960 and 432, both architectures are remarkably similar in terms of their instruction set, essentially taking what it could from the 432 project and putting it into a RISC-y shape. This meant that although the i960 could be mistaken as yet another RISC CPU, as was common in the 1980s, but integrated higher-level features as well, such as additional memory protection and inter-process communication. Continue reading “The I960: When Intel Almost Went RISC”→
The term ‘quantum computer’ gets usually tossed around in the context of hyper-advanced, state-of-the-art computing devices. But much as how a 19th century mechanical computer, a discrete computer created from individual transistors, and a human being are all computers, the important quantifier is how fast and accurate the system is at the task. This is demonstrated succinctly by [Davide ‘dakk’ Gessa] with 200 lines of BASIC code on a Commodore 64 (GitHub), implementing a range of quantum gates.
Much like a transistor in classical computing, the qubit forms the core of quantum computing, and we have known for a long time that a qubit can be simulated, even on something as mundane as an 8-bit MPU. Ergo [Davide]’s simulations of various quantum gates on a C64, ranging from Pauli-X, Pauli-Y, Pauli-Z, Hadamard, CNOT and SWAP, all using a two-qubit system running on a system that first saw the light of day in the early 1980s.
Naturally, the practical use of simulating a two-qubit system on a general-purpose MPU running at a blistering ~1 MHz is quite limited, but as a teaching tool it’s incredibly accessible and a fun way to introduce people to the world of quantum computing.
Remember the scene from Blade Runner, where Deckard puts a photograph into a Photo Inspector? The virtual camera can pan and move around the captured scene, pulling out impossible details. It seems that [Ben Wang] discovered how to make that particular trick a reality, but with audio instead of video. The secret sauce isn’t a sophisticated microphone, but a whole bunch of really simple ones. In this case, it’s 192 of them, arranged on long PCBs working as the spokes of a wall-art wheel. Quite the conversation piece.
At first sight upon seeing [Don]’s HX2023 cyberdeck project one might be sad at the destruction of a retrocomputer, but in fact its classic Epson shell comes from a pile of spare parts left after restoring many other of the classic HX20 notebook computers to working order. The result stays true to the original but gives us so much more in the shape of a Raspberry Pi, and it’s worth cracking it open to see what components make this happen.
The first impression from the pictures is how tidy it all is, with the various USB-based boards contained on a large piece of perfboard spanning the whole case. As well as a USB hub and UPS board there’s an M.2 SSD interface and an audio board, and a DSI color TFT screen neatly fitted in place of the original monochrome item. Finally, there’s an Adafruit keyboard matrix interface board, allowing the use of the Epson’s original keys.
A word of advice: If you see an old direct satellite TV dish put out to the curb, grab it before the trash collector does. Like microwave ovens, satellite dishes are an e-waste wonderland, and just throwing them away before taking out the good stuff would be a shame. And with dishes, the good stuff basically amounts to the bit at the end of the arm that contains the feedhorn and low-noise block downconverter (LNB).
But what does one do with such a thing once it’s harvested? Lots of stuff, including modifying it for use with the QO-100 geosynchronous satellite (German link). That’s what [Sebastian Westerhold] and [Celin Matlinski] did with a commodity LNB, although it seems more like something scored on the cheap from one of the usual sources rather than picking through trash. Either way, these LNBs are highly integrated devices that at built specifically for satellite TV use, but with just a little persuasion can be nudged into the K-band to receive the downlink signals from hams using QO-100 as a repeater.
The mods are simple — snipping out the 25 MHz reference crystal on the LNB board and replacing it with a simple LC bandpass filter. This allows the local oscillator on the LNB to be referenced to an external signal generator; when fed with a 25.78 MHz signal, it’s enough to goose the LNB up to 10,490 MHz — right about the downlink frequency. [Sebastian] and [Celin] tested the mods and found that it was easily able to detect the third harmonics of a 3.5-ish GHz signal.
As for testing on actual downlink signals from the satellite, that’ll have to wait. For now, if you’re interested in satellite comms, and you live on the third of the planet covered by QO-100, keep an eye out for those e-waste LNBs and get to work.
Back in 2020, students from Universidad Del Valle De Guatemala (UVG) pulled off a really impressive feat, designing and building a CubeSat that lasted a whopping 211 days in orbit. In addition to telemetry and radio equipment, it carried a black-and-white camera payload.
But it turns out space is hard. The first pictures were solid black or white, with the automatic exposure process failing pretty badly. A pair of good pictures were taken by waiting until the satellite was passing over Guatemala during sunrise or sunset. A hung I2C bus led to battery drain, and the team tried a system reset to clear the hung state. Sadly the craft never came back to life after the reset, likely because of one of the Lithium-Ion battery cells failed completely in the low charge state.
That was 2020, so why are we covering it now? Because the project just released a massive trove of open source design documents, the software that ran on the satellite and ground station, and all the captured telemetry from the flight. It’s the ultimate bootstrap for anyone else designing a CubeSat, and hopefully provides enough clues to avoid some of the same issues.
Even though the mission had problems, it did achieve a lot of milestones, including the first picture of Earth taken by a Central American satellite. Even coming online and making radio contact from orbit to an earthbound station is quite a feat. The team is already looking forward to Quetzal-2, so stay tuned for more!