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Spectrum Analyser | Telephone Exchange | FORTH Computers | VB Profiler | Wireless Thermostat | Ethernet Receiver | Frequency Synthesizers | Core Memory | Spread Spectrum | Avalanche Pulse Generator | Delta Loop Antenna | Huff & Puff | Duplex Radio-Telephone | GPS Receiver | GPU_FFT

Spectrum Analyser

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.


Telephone Exchange

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.


Mark 1 FORTH Computer

A microcoded stack computer built from discrete logic.

Mark 2 FORTH Computer

Here's another, this time using bitslice and programmable logic devices.

What is FORTH?

Visual Basic Profiler

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.


Wireless Thermostat

Over the mains carrier current remote control for central heating. Unusually for me, this project was mounted in a box!


Ethernet Receiver

Capturing 10BASE-T Ethernet packets using PLL clock recovery.
Left: a capture transient on the VCO control line.


Fractional-N frequency synthesizers

38-76 MHz and 800-1600 MHz fractional-N synthesizers using Spartan 3 FPGA
15-25 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.

Magnetic Core Memory

An experiment to observe the sense output whilst flipping the state of a single bit in an early Univac III magnetic core memory plane.


Spread Spectrum Link

Experimental direct sequence spread spectrum (DSSS) voice link.


Avalanche Pulse Generator

500 pico-second rise and fall time with one transistor!


Delta Loop Antenna

A water-resistant back-garden HF receiving loop for general shortwave listening.


Huff & Puff VFO Stabiliser

A "fast" Huff & Puff VFO stabiliser using a CPLD.


A Portable Duplex Radio-Telephone (PDF)
Lewis and Milner; THE WIRELESS ENGINEER; September, 1936.

"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.


Homemade GPS Receiver

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.


GPU_FFT

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.