direction finding circui

Build a hanging dipole for two metres - Described here is a simple omnidirectional, vertically-polarised dipole for two metres

A comparison of commercial 4m verticals - Ian Hogan G6TGO has recently tried out two different commercially-built vertical aerials for 4m, and has prepared this article to share his findings with us.

K0FF's 6 meter SLOOP antenna - It is more or less omni-directional, and horizontally polarized, it's just a dipole folded around on itself, and supported at the far (open) end with a plastic insulator.

Build a Basic Beverage Antenna - Basically the Beverage is a travelling wave antenna made of a length of wire a small height (relative to the wavelength of interest) above earth. It can be terminated for unidirectional reception or left unterminated for bi-directional reception.

The Simple Collinear - Wherever there is a need for a vertically polarized omni-directional antenna with gain, a collinear is used. The vertically polarized collinear takes the form of two or more half waves in-line and in-phase, resulting in an omni-directional pattern with maximum radiation near the horizon.

Omni-Gain Vertical Collinear Antenna - This rugged antenna, an omnidirectional collinear, is capable of surviving harsh environments. It's a good choice for repeater installations and can be top, or side mounted to the tower by WA6SVT

Home-brew Compact 6dBi Collinear Antenna  ^pop - This page details the construction of an easy-to-make collinear 360 degrees omni-directional, vertically polarised, antenna for 802.11b/g wireless networking.

Short Whip Antenna Tuner - Here is a circuit that will resonate a short whip antenna for the HF Bands.

ZL1BPU Rotator Controller - A very simple controller circuit, with fairly smart performance! The ZL1BPU Rotator Controller has been designed as an add-on unit for the popular Kenpro KR-400 and Yaesu G-400 rotators. The controller consists of a small circuit board which fits inside the rotator control box (see picture).

Emtech ZM-2 Antenna Tuner Kit - The Emtech ZM-2 Antenna Tuner is a nifty little portable transmatch for QRP (low power). It utilizes the well-known Z-match circuit, which is especially useful for balanced antennas (like dipoles and loops).

K6XX CW Indicator Kit - The purpose of this circuit is to light a LED in your radio when you tune to within +- 20hz of a cw signal. This makes for easy tuning of a cw signal by eye rather than by ear

Is HF propagation reciprocal - Some test circuits using the ACE-HF System Simulation & Visualization software, about reciprocal propagation on HF bands by NW7US

RF Circuit design basics - Ebook by Akira Matsuzawa Tokyo Institute of Technology, Building blocks in RF system and basic performances, Device characteristics in RF application , Low noise amplifier design, Mixer design and Oscillator design

Shortwave Converter - This is a simple circuit that when placed near an ordinary AM broadcast radio will allow you to receive international shortwave broadcasts in the 5-6 MHz band

DesignWorks - Commercia, productive and easy-to-use electronic circuit schematic drawing tool Featuring full hierarchical design, standard and custom netlist formats, extensive symbol libraries, scripting and customization features and much more.

ViPEC Network Analyzer - This program intended for electronic circuit analysis (mainly for Linux). ViPEC is a powerful tool for the analysis of high frequency, linear electrical networks.

Target 3001 PCB Design - Represents a new generation of CAD/CAE software for circuit design. Has been created to meet the requirements of professional design engineers.

Qucs - Quite Universal Circuit Simulator Priority listing - Qucs, briefly for Quite Universal Circuit Simulator, is an integrated circuit simulator which means you are able to setup a circuit with a graphical user interface (GUI) and simulate the large-signal, small-signal and noise behaviour of the circuit. After that simulation has finished you can view the simulation results on a presentation page or window. Run on Linux.

AA Battery Solar Charger - This almost trivial circuit may be used to charge a pair of AA or AAA sized rechargeable battery cells from sunlight.

TANKIT Priority listing - A free design aid for vacuum tube linear RF power amplifiers. Determine plate circuit operating parameters and design pi or pi-L tanks quickly and easily.

Audio processor for SSB transceiver - This circuit consists of microphone amplifier and a high pass filter. Suitable to improve signal readability.

A low cost UHF/VHF duplexer - Duplexers for dual band radio are usually high pass filter and low pass filter combined in the same box. This circuit is a design within a cost of US$10.

FM Morse Code Keyer - A simple circuit which will generate a 700 Hz tone into any FM transceiver allowing an amateur to practice CW with another amateur on a 2 meter simplex frequency.

Signal Generation Solution - Build an inexpensive RF signal generator

A reliable VOX PTT circuit - This VOX PTT has been designed with Echolink in mind, but it will work equaly as well with repeaters