signal

Technology Connections explains why car turn signals appear to drift out of sync at stoplights and how thermal and other flasher designs work. It also covers how synchronization could be achieved.

A This Week in Startups episode in which Jason Calacanis interviews David Heinemeier Hansson of 37signals. They discuss bootstrapping, company philosophy and views on the tech industry.

Technology Connections explains why North American tail light rules, which allow red turn signals and flashing brake lights, make signals ambiguous. He argues for amber signals and cites studies showing a safety benefit.

CNLohr maps Wi-Fi signal strength at high resolution by moving an ESP8266 on a CNC mill, then visualizes the 3D data in WebGL. The result shows interference patterns in space.

3Blue1Brown's animated visual introduction to the Fourier Transform, showing how a signal breaks into frequency components.

An episode of This Week in Startups in which Jason Calacanis interviews Ruby on Rails creator David Heinemeier Hansson. They discuss startups, bootstrapping and 37signals' approach to business.

Reducible's visual walkthrough of the Fast Fourier Transform, motivated by polynomial multiplication. It shows how the FFT's key ideas can be discovered by asking the right questions.

3Blue1Brown shows how the uncertainty principle arises from Fourier transforms. A wave packet cannot be narrow in both position and frequency, so the principle is a property of waves rather than of measurement.

Veritasium tells the story of the Fast Fourier Transform, from its use in detecting nuclear tests to Cold War politics, and how it could have changed the arms race. It includes a short, intuitive explanation of what the Fourier transform does.

An MTA video on communications-based train control, the system meant to replace the New York City subway's century-old signaling. It also shows the mechanical interlocks and signals in use today.

MIT researchers show that sound can be recovered from silent video by analyzing tiny vibrations in objects such as a potato chip bag. It works even with consumer cameras by using rolling shutter.

Rick Hartley gives a roughly two-hour live training on proper grounding in PCB design. He explains how energy actually flows in the space between conductors, and how that governs noise, EMI, return paths and signal reflections.

Ben Eater explains how VGA signals work and builds a breadboard circuit that produces correct sync timing so a monitor recognizes the signal. He then builds toward displaying an image from simple logic chips.

AlphaPhoenix uses a custom high-speed measurement setup to watch voltage waves travel down wires and split at a fork. It answers how electricity knows where to go and how quickly that process happens.

Technology Connections explains why the superheterodyne radio has its name and how mixing frequencies lets it tune stations well. It walks through the underlying wave phenomena and algebra and why the design solved a hard tuning problem.

David Heinemeier Hansson, creator of Ruby on Rails and partner at 37signals, argues that planning is guessing and startups should focus on today. He says constraints are an advantage and that startups can bootstrap profitably in sizable markets.

Linus Tech Tips tests whether chaining many PCIe riser extensions causes loss of GPU performance. They keep adding extensions to see how far the signal will go.

Shahriar of The Signal Path tears down and experiments with Keysight's UXR real-time oscilloscope, which offers 110GHz bandwidth and 256GS/s sampling, and compares architectures from Keysight, LeCroy and Tektronix.

The Signal Path takes apart a Starlink dish layer by layer, analyzing the phased array RF design, system architecture and integrated circuits, with an X-ray of the RF stack.

A Bell Labs film in which Dr. J.N. Shive uses a mechanical wave machine to demonstrate reflection, standing waves, resonance and impedance matching. He includes some equations but relies mostly on real-world examples a layperson can follow.

David Heinemeier Hansson's talk at Startup School 2008 on building a profitable startup. He argues for bootstrapping and small, well-run companies instead of chasing investment and exits.

Rick Hartley's AltiumLive keynote on differential pairs in PC boards. He argues the rules from cables and twisted pairs do not carry over, and covers which pair geometry gives the best impedance control, the right spacing, routing practice and how much skew is acceptable.

Monty Montgomery of Xiph.org gives real-time demonstrations of sampling, quantization, bit depth and dither using real audio equipment, including both digital analysis tools and vintage analog bench gear. It shows that sampled audio is not stair-stepped and corrects common misconceptions about digital audio.

The first of four short videos from Bill Hammack (engineerguy) introducing and giving the history of a 100-year-old mechanical computer, Michelson's harmonic analyzer. The series goes on to explain Fourier synthesis, analysis and operation of the machine.

Mike Pound explains the discrete cosine transform and how it underpins JPEG compression. It is part two of Computerphile's JPEG series.

David Kriesel's 31C3 talk, in German, on the discovery that Xerox scanner-copiers silently replace digits and letters in scanned documents. He explains how the bug stayed unnoticed in the wild for years.

Huygens Optics explains the Fourier transform and shows how a lens performs one optically. A DLP projector is used as a Fourier filter to do simple pattern recognition on lithographic character patterns.

Tom Scott explains for Computerphile how Unicode and UTF-8 grew out of messy older character encodings to become the web's standard. It covers why the design works and how it handles worldwide text.

3Blue1Brown introduces Fourier series, from the heat equation to drawing arbitrary shapes with rotating circles. It builds a visual intuition for decomposing functions into sine waves.

David MacKay's 2007 Google Tech Talk presents Dasher, a text-entry system driven by continuous gestures and a language model, reaching about 35 words per minute with one finger and 25 hands-free. It explains the information-theory reasoning behind the design.

3Blue1Brown's discovery-oriented introduction to error correction codes, building up Hamming codes from the puzzle of locating a flipped bit. It explains the parity-check idea and why it is so efficient.

Tom Scott explains why confetti and snow wreck video quality, using interframe compression and bitrate. He demonstrates it live by changing the quality on screen.

Moxie Marlinspike speaks at Next Generation Threats 2014 about the challenges of encrypted communication and how Signal addresses them. He also draws on American action movies as narrative for secure communications.

A two-minute demonstration of the loudness war, showing how heavy dynamic range compression in CD mastering makes music louder while degrading sound quality. It uses audio examples so you can hear the distortion.

The first lecture of David MacKay's Cambridge course on information theory, pattern recognition and neural networks. It introduces the core ideas of his book Information Theory, Inference, and Learning Algorithms.

A short animation reconstructing a planet's looping orbit using Ptolemy's epicycles and deferents, with the epicycles tracing out the face of Homer Simpson. It shows how enough circles can reproduce nearly any shape.

Timur Doumler's CppCon 2015 talk on how C++ is used in the audio industry. It covers the patterns and tools audio developers rely on, including handling real-time constraints.

A Justin Bieber song slowed down 800% with the PaulStretch program, turning a pop track into a long ambient drone.

Course outline for Stanford's online GNSS course, introducing how GPS works and the many uses of satellite navigation. The series pairs short lectures with backyard experiments using smartphones.

Onslaught's Bad Apple 64 is a Commodore 64 demo that streams over 2000 frames of the Bad Apple animation from a single disk side at 12fps, with each frame packed to around 70 bytes.