Al Williams writes about the surprising continued availability of Reverse Polish Notation calculators in 2026, despite RPN losing the mass market to algebraic entry decades ago. RPN uses a stack-based system where operators follow their operands, eliminating the need for parentheses or an equals key. Today's options range from the still-sold HP-12C to SwissMicros' modern enthusiast machines, DIY builds on ATmega and ESP32 hardware, and a thriving ecosystem of phone and desktop apps.
- The first RPN calculator was the Friden EC-130 (1964), a 44-pound desktop unit at $2,150 whose CRT displayed all four stack levels simultaneously
- SwissMicros' R47, at ~$300, features an 8-level stack, built-in electrical engineering functions, and firmware still officially in beta
- HP released a native Linux build of HP Prime as a 2019 AppImage, but it predates the Python programming addition; the only way to get Python on Linux is running an older Windows version under Wine with Soda 9 in Bottles, and you must not let it update
- Alex Garza's PAXER kits reproduce HP-15C/16C/41C on ATmega328 for under $100, adding continuous memory, backlight, and real-time clock
- The 10LC turns a ~$50 ESP32-based M5Stack Cardputer into a pocket RPN calculator
- Free42, a clean-room HP-42S implementation by Thomas Okken, runs on Android, iOS, Windows, macOS, and Linux
- The first RPN calculator was the Friden EC-130 (1964), a 44-pound desktop unit at $2,150 whose CRT displayed all four stack levels simultaneously
- SwissMicros' R47, at ~$300, features an 8-level stack, built-in electrical engineering functions, and firmware still officially in beta
- HP released a native Linux build of HP Prime as a 2019 AppImage, but it predates the Python programming addition; the only way to get Python on Linux is running an older Windows version under Wine with Soda 9 in Bottles, and you must not let it update
- Alex Garza's PAXER kits reproduce HP-15C/16C/41C on ATmega328 for under $100, adding continuous memory, backlight, and real-time clock
- The 10LC turns a ~$50 ESP32-based M5Stack Cardputer into a pocket RPN calculator
- Free42, a clean-room HP-42S implementation by Thomas Okken, runs on Android, iOS, Windows, macOS, and Linux
Zoe Skyforest writes about a collation by Ian Y.E. Pan of Emacs appearances in popular culture, spanning films, TV, anime, and comics. The list highlights how the classic *nix text editor has become a recognizable cultural touchstone alongside its rival vi, though it is acknowledged to be far from exhaustive.
- In *The Social Network*, Zuckerberg uses Emacs to write a website scraper
- *Silicon Valley* features Emacs more than once
- Japanese anime *Key The Metal Idol* includes an Emacs reference
- Hackaday invites readers to submit a similar list for vi
- In *The Social Network*, Zuckerberg uses Emacs to write a website scraper
- *Silicon Valley* features Emacs more than once
- Japanese anime *Key The Metal Idol* includes an Emacs reference
- Hackaday invites readers to submit a similar list for vi
Tyler August writes about eenk, a project that brings long-form text adventures'' think Zork with several novels' worth of prose' 'to palm-sized Xteink e-ink readers. Built on the ESP32 microcontroller and the ink scripting language, it ships with its own IDE (eenky) for authoring choose-your-own-adventure books and is released under an MIT license on GitHub.
- The X3/X4 use an ESP32-C3 with no PSRAM, giving developers less memory than 1980s home computers
- The X4 Pro variant uses an ESP32-S3 for more RAM and adds a touchscreen
- Commenters note Xteink sells identical hardware through different channels with different software configurations (locked vs. unlockable)
- A commenter suggests packaging the project as a Crosspoint plugin rather than a standalone firmware to avoid repeated reflashing
- The X3/X4 use an ESP32-C3 with no PSRAM, giving developers less memory than 1980s home computers
- The X4 Pro variant uses an ESP32-S3 for more RAM and adds a touchscreen
- Commenters note Xteink sells identical hardware through different channels with different software configurations (locked vs. unlockable)
- A commenter suggests packaging the project as a Crosspoint plugin rather than a standalone firmware to avoid repeated reflashing
Maya Posch writes about the LC harmonic filters at HVDC converter stations, which scrub the noisy AC sinewave produced after line-commutated HVDC-to-AC conversion. Drawing on a video by Jordan Taylor (The Electric Brit), the piece walks through a UK-based converter station to explain what these filters are, how they work, and why their design at grid scale is a distinct engineering challenge.
- The distortion introduced by HVDC-to-AC conversion is directly analogous to the harmonics in a much lower-voltage power supply, making the fix (an LC filter) conceptually the same, just orders of magnitude larger.
- The same massive inductors and capacitors that form the filter also absorb and generate reactive power on the AC grid, damping oscillations and adding a secondary layer of stability.
- The distortion introduced by HVDC-to-AC conversion is directly analogous to the harmonics in a much lower-voltage power supply, making the fix (an LC filter) conceptually the same, just orders of magnitude larger.
- The same massive inductors and capacitors that form the filter also absorb and generate reactive power on the AC grid, damping oscillations and adding a secondary layer of stability.
Bryan Cockfield writes about the Kiwix open-source project, which started as an offline backup for Wikipedia and now includes other sites like StackExchange.To preserve and serve information from personal hardware, ensuring survival through internet outages and website disappearances, Kiwix is available on Linux (Docker compatible), Windows, Android, and Apple platforms.
- A separate tool called Zimit is required to generate the .zim archive files that Kiwix serves.
The Kiwix organization hosts pre-downloaded .zim files of common sites, sparing users from crawling Wikipedia themselves, a task that could take months on limited consumer hardware.
- The article points to a prior piece on building an "armageddon-proof" Raspberry Pi briefcase as suggested hosting hardware.
- A separate tool called Zimit is required to generate the .zim archive files that Kiwix serves.
The Kiwix organization hosts pre-downloaded .zim files of common sites, sparing users from crawling Wikipedia themselves, a task that could take months on limited consumer hardware.
- The article points to a prior piece on building an "armageddon-proof" Raspberry Pi briefcase as suggested hosting hardware.
Fenix Guthrie writes that Chris Staecker restored a remarkably well-preserved Digi-Comp 1, the 1963 programmable educational toy computer introduced by E.S.R. The device uses mechanical logic gates programmed with soda-straw-like tubes on sliding rails and spring-loaded levers actuated by a clock switch to compute simple binary functions as a non-Turing-complete state machine reflective of early 1960s computing.
- E.S.R. originally intended to make actual computers before becoming a premier educational toy company in the 1960s
- Staecker'''s restoration used rubber bands and 3D-printed parts to return the toy to working condition
- The machine has 88 states, equivalent to 16,777,216 possible configurations
- Article references successor Digi-Comp II and other vintage ''"sort of''" computers like Geniac
- E.S.R. originally intended to make actual computers before becoming a premier educational toy company in the 1960s
- Staecker'''s restoration used rubber bands and 3D-printed parts to return the toy to working condition
- The machine has 88 states, equivalent to 16,777,216 possible configurations
- Article references successor Digi-Comp II and other vintage ''"sort of''" computers like Geniac
Tyler August writes that The Masked Bear's open-source wifisense-pi project uses an ESP32-S3 sampling the 2.4 GHz WiFi channel 100 times per second with a Raspberry Pi 4 for signal processing to detect subtle body motions via WiFi disturbances, effectively sensing breathing or presence through walls without dedicated hardware.
- Can detect a perfectly still human by breathing, but presence can be hidden by holding breath
- Single sensor provides no position information and cannot reliably distinguish one vs multiple people
- Works by sniffing existing 2.4 GHz signals and functions through walls
- Not the first WiFi-based presence project; prior work includes ESP32 person sensors and millimeter-wave alternatives
- Can detect a perfectly still human by breathing, but presence can be hidden by holding breath
- Single sensor provides no position information and cannot reliably distinguish one vs multiple people
- Works by sniffing existing 2.4 GHz signals and functions through walls
- Not the first WiFi-based presence project; prior work includes ESP32 person sensors and millimeter-wave alternatives
The author is undertaking a project to develop "Bridgetris," a game for the vintage 1985 BBC Bridge Companion console originally intended to teach bridge via television. To achieve this, the creator must master Z80 assembly language, reverse-engineer the system BIOS to allow custom code execution from cartridges, and perform hardware modifications like composite video integration.
- The device uses the TMS9129 VDP which features 16kB of VRAM.
- Original retail price was approximately £200 in 1985.
- Hardware was originally designed by a company named Heber Ltd.
- A composite video mod was implemented to improve visual quality on modern displays compared to the original RF output.
- The device uses the TMS9129 VDP which features 16kB of VRAM.
- Original retail price was approximately £200 in 1985.
- Hardware was originally designed by a company named Heber Ltd.
- A composite video mod was implemented to improve visual quality on modern displays compared to the original RF output.
Zoe Skyforest writes about Kek, an emulator developed by vanheusden to bring the influential 16-bit PDP-11/70 minicomputer back to life on modern hardware. The software supports a variety of platforms including Linux, Windows, and microcontrollers like the ESP32 or Teensy 4.1.
- Emulates classic disk drives such as RK05, RL02, RP06, and RP07.
- Supports KW11-L line time clocks and DC-11 serial interfaces.
- Capable of running Unix versions from version 5 through version 7 in multi-user mode.
- Emulates classic disk drives such as RK05, RL02, RP06, and RP07.
- Supports KW11-L line time clocks and DC-11 serial interfaces.
- Capable of running Unix versions from version 5 through version 7 in multi-user mode.
Al Williams writes that International Reply Coupons (IRCs) are nearing their end as the Universal Postal Union prepares to phase them out by December 31, 2026. Once essential for radio hobbyists and international mailers, these coupons allowed individuals to pay postage in one country that could be exchanged for local stamps in another, but modern digital communication has rendered such physical vouchers nearly obsolete.
- Radio enthusiasts used the system primarily to receive QSL cards from foreign stations without requiring senders to cover international shipping costs.
- The Universal Postal Union consists of an association of post offices across 192 countries.
- Charles Ponzi's original scheme involved exploiting price discrepancies for these coupons between different nations.
- Radio enthusiasts used the system primarily to receive QSL cards from foreign stations without requiring senders to cover international shipping costs.
- The Universal Postal Union consists of an association of post offices across 192 countries.
- Charles Ponzi's original scheme involved exploiting price discrepancies for these coupons between different nations.
