security alarm circuit

Active HF antenna - An active HF receiving antenna circuit by G7BCJ

A homebrew 10-element 900 MHz quagi - A 10 elements quagi antenna for 900 mhz

Optimizing Inductors - While intended mainly for antenna loading coils, this article also applies to other resonant systems, such as amplifier tank circuits.

WiNRADiO Communications - WiNRADiO Communications manufacture radio communications equipment for a very wide range of applications. Our customers include professional communications radio users in government, military, security, surveillance, spectrum monitoring organizations, telecommunications, industry, as well as radio and computer enthusiasts.

RACOM - Radio modems - RACOM is a Czech company specialized in design and production of radio modems and other devices for wireless data networks for radio channels from 140 to 900 MHz. RACOM radio data networks are suitable for data transfer in telemetry & SCADA applications, transaction networks, security systems, IP networks and firts of all mobile tracking and fleet management.

Far Circuits - Printed Circuit Boards - FAR Circuits is exclusively a manufacturer of Printed Circuit Boards for electronic projects that are used by the Amateur Radio and electronic hobby enthusias

Sunstone Circuits Priority listing - Sunstone Circuits is your easiest source for quoting and ordering printed circuit boards online. We are three respected brands in one: PCBexpress quickturn boards, PCBpro.com full-featured and design-checked boards, and PCB123 design software.

VLF-LF And the Loop Aerial - The article discusses the theory of loop aerials for receiving and how they reduce the level of local noise. A Loop Aerial is described suitable for use on the LF and VLF bands together with a circuit of an interface loop tuner and preamplifier. The discussion extends to the problems of amplifier noise and the advantages of tuning the loop.

Antenna Noise and Signal Cancelling at LF - The fact that the phasing between a wanted signal and an unwanted signal can be different on different antennas is put to advantage. With this condition, the unwanted signal can be cancelled out by controlling amplitude and phase. The heart of the system is some form of phase control circuitry.

Far circuits - Direction finding projects, useful tools for t-hunting operations

HRX80 80 meters receivers for APRS - 80-meter peilontvanger / receiver includes printed circuit sample and list of components

Qsk keying for yaesu radios - QSK amplifier keying circuit for Yaesu FT-1000MP, FT-1000MP Mk-V, FT-1000/1000D and FT-920

Sydney Scanner Frequencies - One of the best compilations of frequencies in Sydney particularly SW. Include Police, other emergency people, Marine, the entire aircraft list for Sydney, RAAF squadron frequencies, UHF CB frequencies as well as a heap of miscellaneous frequencies like security, shoppin malls etc.

FM transmitter kit for 88-108 Mhz - 3 Watt fm Transmitter Hobby Kit 88 - 108 Mhz. Kit Includes Glass Fibre Printed Circuit Broad High Quality Componets Full Instructions

Circuit Specialists - We specialize in pc-based data acquisition systems, test equipment, electronic components, disk on modules, choke and coils, diodes, capacitors and connectors, potentiometers, crystals, resistors, relays

Smith Chart Software - SimSmith is a highly interactive, real time Smith chart graphing program. Circuits are constructed using drag-n-drop. Load files can be imported from the EZNEC and CocoaNEC antenna simulation software and from the AIM4170 and miniVNApro antenna analyzers. Circuits and load files can be of any size. Key Features: SimSmith is one of the few Smith chart packages which models transmission line losses. SimSmith also allows the description of circuit elements using algebraic equations. SimSmith has only one screen and allows the screen to be resized to increase workspace or readability.

TCube - TCUBE is a combination of a Spectrum Analyzer and a Two Tone Generator, with optional quadrature outputs. It can be used for measuring the intermodulation behavior of an audio circuit, and as a general purpose tool

Constant Current Battery Charger - Constant Current Battery Charger circuit project

OZ2M - Beacon Keyer  ^updated - Circuit and software to build a beacon keyer, includes downloadable packages.

Delabs technologies Product Design and Engineering - Around 200 electronic circuits in pdf format or images, There are also over 1000 links to useful electronics, freeware, open source websites. There are some 100 useful documents, software and pcbs too. Mainly industrial electronics, instrumentation. Covers Various aspects of electronics and basics of circuit design.

Making printed circuits - To make smart looking PCB's, all you need is a computer, a laser printer, copper clad board, etchant, a clothes iron and some Epson glossy photo paper.

A low pass filter circuit - A simple 7 element, Chebyshev low pass filter, rolls of at 30MHz. Attenuation is better than -40dB at 60MHz, -65dB at 90MHz, -80dB at 120MHz.

Bowden's Hobby Circuits - A small collection of electronic circuits for the hobbyist or student. Site includes over 100 circuit diagrams, links to related sites, commercial kits and projects, newsgroups and educational areas. Most of the circuits can be built with common components available from Radio Shack or salvaged from scrap electronic equipment

A CW TX for 80 meters band - This simple circuit will give about 1.2 Watts of output when powered from a 13.8VDC supply.

Antenna Noise and Signal Cancelling at LF - By using the signals from two antennas, controlling their relative amplitudes and controlling the phase of one of them, unwanted signal or unwanted noise can be phased out. Circuitry is described which uses the signal from a wire antenna to provide selective cancelling against the signal output from an LF loop antenna.