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Notes on making the W2DU choke balun by placing several ferrite sleeves around a coaxial cable.

Inverted vee dipole antenna for 20 meters band by VK1OD

The 1:4 balun is of particular interest because it underlies many other configurations, and understanding it helps towards understanding the other Ruthroff balun configurations.

A model of a Guanella 1:1 VHF choke balun using a FT140-61 core

This article proposes a lossy transmission line model of a practical Guanella 1:1 balun that is effective for all frequencies within and immediately adjacent to the pass band

This article documents an unobtrusive antenna for operation on 7MHz, primarily for contacts with stations at up to 1000Km range.

The Double Bazooka Dipole is a half wave dipole with an attempt at compensation of the reactance change that occurs around resonance for a half wave dipole.

This article reviews the proposition that a 4:1 current balun in the style of Guanella can be constructed with both pairs of windings sharing a common magnetic circuit.

This is a simple calculator for solving the antenna wire catenary between to end points given the design wind speed, mass per unit length of the wire, wire diameter and Gross Breaking Strength of the wire.

This article explores a theoretical model for the losses of an 80m / 40m trapped inverted V dipole antenna system using a bootstrap coax trap, but does not examine the pattern of the antenna.

This article describes the design of an antenna for local contacts on 7MHz, including a simple and efficient matching system that presents a 50 ohm load to the transceiver.

This calculator computes the matched line loss for a transmission line using a model calibrated from data for the transmission line types built in to the calculator. It also gives an estimate of the mismatched loss if the mismatch is specified.

Feeding a G5RV Overview by VK1OD

This is an Excel spreadsheet template to design DL6WU Yagi antennas

This article describes the 144MHz horizontally polarised antenna at VK1OD in November 2008. The antenna uses two identical four element arrays that were constructed around 1970

This article describes a simple device to generate Roger Beep tones.

Optimising a typical G5RV antenna by VK1OD

This article explores the Cobra Junior linear loaded antenna for 80m to 10m bands. This antenna is a linear loaded dipole described by W4JOH in 73 magazine June 1997

The 5/8 vertical it quite popular and matching solutions can vary

This article describes a simple Inverted L antenna for the HF bands designed to work on 80m, 40m, 30m and 20m

This article explores the performance of an unloaded elevated vertical, base matching and feed line as a multi-band HF antenna system.

This article examines the performance of the Ameritron AL-811H amplifier with the supplied 811A tubes and with 572B tubes, and details a procedure for replacement of existing tubes.

Analysis of an antenna trap where a coil is formed of a length of coax cable, the outer conductor of one coax end is tied to the inner conductor of the other coax end, and the remaining connections form the terminals for the trap.

This article explores the performance of an unloaded vertical as a multi-band HF antenna.

A novel approach to contruction of a gamma match.

Understanding Baluns. This article explores some simple antenna system configurations and the effect of key system components, connections and dimensions on feed line common mode current.

This article contains notes on installation of a Roger Beep for an Icom IC7000 transceiver for use with a Heilsound Traveller headset.

The Yaesu FL2100Z is a HF linear amplifier rated for 1200W PEP input, and using two 572B triode tubes. This article explores the recommended operating conditions, and alternatives.

Graph of the frequency response of some of the legendary microphones favoured by radio hams

This article describes a generalised unit for interfacing a transceiver's TTL/CMOS interface to RS-232.

PEP RF output power measurement, and examples RF output power measurements

Approximately 2.8% annual decline in Australian amateur radio licenses was observed over the five years leading up to 2002, a trend that prompted further analysis of the country's amateur population. This resource examines licensing statistics and demographic shifts within the Australian amateur radio community between 1998 and 2007, utilizing available data to identify patterns in license issuance and renewal. The study focuses on **population trends** and the underlying factors contributing to changes in the number of active **amateur radio operators**. It provides insights into the health and growth trajectory of the hobby in Australia during this specific period. Understanding these demographic shifts is crucial for clubs, regulatory bodies, and equipment manufacturers to adapt strategies and foster engagement.

Performance of an unloaded ground mounted vertical as a multi-band HF antenna.

Broadband over power lines (BPL) is a technique for transmission of high speed data (broadband Internet) over powerlines. Access BPL technology injects radio frequency energy into powerlines which were not designed for transmission of radio frequency energy, and leak substantial energy that causes interference to radiocommunications service

137.7 kHz QRSS beacon exciter is described, utilizing a single chip for operation on the 2200m amateur band. The design focuses on simplicity and efficiency for weak signal applications, providing a compact solution for generating QRSS signals. This project targets the DX portion of the band, enabling long-distance communication with minimal power output. The resource details the construction and functionality of the **QRSS beacon**, emphasizing its **low-power operation** and suitability for experimental amateur radio. It provides insights into the circuit's architecture and potential for integration into existing station setups. The design aims to offer a practical and accessible entry point for amateurs interested in weak signal modes on the LF/MF bands.

Comment on W5DXP 2011 coil measurement experiment

This calculator estimates the efficiency of a T match tuner using a simple loss model.

1.5 dB of matched line loss can be calculated for a given transmission line using this online tool, which employs a model calibrated from empirical data. The calculator allows radio amateurs to input specific transmission line types, such as _RG-8_ or _RG-58_, and then determine the expected signal attenuation. This is crucial for optimizing antenna system efficiency and understanding power delivery to the radiating element, especially for HF and VHF operations where feedline losses can significantly impact performance. Beyond matched loss, the calculator also provides an estimate for mismatched loss if the Standing Wave Ratio (SWR) is specified. This feature helps operators quantify the additional power loss due to impedance discontinuities between the transceiver, feedline, and antenna, which is a common concern in amateur radio installations. Accurate loss calculations are vital for effective station design and for predicting actual radiated power. The tool's utility extends to various operating scenarios, from fixed station setups to portable deployments, aiding in the selection of appropriate feedline lengths and types to minimize signal degradation. Understanding these losses is a fundamental aspect of maximizing the effectiveness of any amateur radio antenna system.

A collection of articles related to my pursuit of the hobby of Amateur Radio.

VK1OD informations on BPL

NFM (for Noise Figure Meter) is a software application to assist Noise Figure measurement. NFM implements the method of Agilent application notes AN 57-1 and AN 57-2 for noise figure measurement, but with the addition of an adjustable attenuator after the noise source and between the DUT and instrument.