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This DC to 50 MHz spectrum analyser uses a standard oscilloscope for display. Dynamic range is better than 70dB using the received signal strength indicator (RSSI) of an FM demodulator IC. |
This miniature, 8-line home telephone exchange (PABX) works with standard telephones and features high-quality, user-friendly progress tones and AC ringing. The exchange is all solid-state: no relays. |
A microcoded stack computer built from discrete logic. Here's another, this time using bitslice and programmable logic devices. What is FORTH? |
Here's a software project. This profiler will help you optimise the performance of middle-tier Visual Basic DLLs running under ASP, Microsoft Transaction Server (MTS) on NT4 and Component Services (COM+) on Windows 2000. You can also profile VB Form executables. |
Over the mains carrier current remote control for central heating. Unusually for me, this project was mounted in a box! |
Capturing 10BASE-T Ethernet packets using PLL clock recovery.
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Fractional-N frequency synthesizers38-76 MHz and 800-1600 MHz fractional-N synthesizers using Spartan 3 FPGA15-25 MHz fractional-N synthesizer with 1 Hz steps Fast & accurate behavioral PLL simulator Reducing PWM distortion phase noise in fractional-N synthesizers (PDF) My first fractional-N frequency synthesizer RACAL RA1792 synthesizer. Dana Digiphase synthesizer. |
An experiment to observe the sense output whilst flipping the state of a single bit in an early Univac III magnetic core memory plane. |
Experimental direct sequence spread spectrum (DSSS) voice link. |
500 pico-second rise and fall time with one transistor! |
A water-resistant back-garden HF receiving loop for general shortwave listening. |
A "fast" Huff & Puff VFO stabiliser using a CPLD. |
A Portable Duplex Radio-Telephone (PDF) "A practical system of duplex radio-telephony [...] in which each set is made alternately transmitter and receiver at a supersonic frequency. The interrupted oscillation provides super-regenerative amplification [...] The quench frequency must be selected according to the distance between the sets." |
Duplex Radio-Telephone (Revisited) Re-creating Lewis and Milner's 1930's experiments with modern (well, 1970's) components. They used just two valves! This design employs four 4000-series CMOS ICs and a dual-gate MOSFET to achieve full-duplex telephony with phase-locked quench oscillators. |
A homemade GPS receiver built from the ground up using discrete components and featuring a limiting IF followed by 1-bit ADC ahead of DSP signal processing in a Xilinx Spartan 3 FPGA. Fast FFT-based search, and navigational solutions computed by "C" code on Windows and Linux. May 2013: 12-channel, battery-powered, truly-portable Raspberry Pi version. September 2014: Source re-released under GNU GPL. |
An FFT library for the Raspberry Pi which exploits the BCM2835 GPU V3D hardware to deliver ten times more data throughput than is possible on the 700 MHz ARM. |
A cycle-accurate 6502 microprocessor core in Verilog HDL, automatically generated from the transistor-level netlist. |
Direct Digital Phase Noise Measurement High-quality, low-cost measurement of oscillator and signal generator phase noise, using (mostly) off-the-shelf hardware. |
Copyright © Andrew Holme, 2003. |