End fed matching – PA3HHO design review #2

  A correspondent having read End fed matching – design review raised a similar design by PA3HHO which uses a#43 ferrite toroid as part of an end-fed matcher, see Multi band end-fed (English). Further to End fed matching – PA3HHO design review , this article has a solution to PA3HHO’s “original 40/20/10 version” using FT140-43 with … Continue reading End fed matching – PA3HHO design review #2

Reconciling my #52 choke design tool with G3TXQ’s measurements

A correspondent wrote with concern of the apparent difference between graphs produced by my #52 choke design tool with a graph published by G3TXQ of his measurement of 11t on a pair of stacked FT240-52 cores. I published a note earlier about my concerns with a similar graph by G3TXQ compared to the Fairrite datasheet, … Continue reading Reconciling my #52 choke design tool with G3TXQ’s measurements

Low Insertion VSWR HF Guanella 1:1 balun for instrumentation

The article describes a current balun intended for measurement use with low power instrumentation. It is lightweight and can be made with materials readily available in Australia (LF1260 cores are a little over $1 each in packs of six). The target application is for a 600mm square small loop for field strength measurement below 15MHz. … Continue reading Low Insertion VSWR HF Guanella 1:1 balun for instrumentation

Exploiting your antenna analyser #10

Measuring an RF inductor This article walks through practical measurement of a ferrite toroidal inductor using an antenna analyser. To be relevant practically, lets use an example from N4SPP’s end fed wire antenna on 3.6MHz. His coupling transformer uses a two turn winding on an FT240-43 core for the nominal 50Ω connection to the antenna … Continue reading Exploiting your antenna analyser #10

Underhill on Small Transmitting Loop efficiency

The meaning of the terms efficiency and radiation resistance are often critical to understanding written work on antennas, yet different authors use them differently, often without declaring their intended meaning. Mike Underhill (G3LHZ) is an enthusiastic proponent of Small Transmitting Loops and in his slide presentation (Underhill 2006) challenges the proposition that their efficiency is … Continue reading Underhill on Small Transmitting Loop efficiency

Differential flux leakage in a Guanella 1:1 balun – an experiment

The article reports a simple experiment on the balun described at Low power Guanella 1:1 tuner balun using a pair of Jaycar LF1260 suppression sleeves to assess the loss with near zero common mode current. This test would not subject dielectrics to high electric field strength. The balun above had the two wires at one … Continue reading Differential flux leakage in a Guanella 1:1 balun – an experiment

End fed matching – design review

A correspondent asked me to review an end fed matching unit that uses a FT82-43 ferrite transformer to transform the high impedance of a 40m end fed half wave down to approximately 50+j0Ω. His design uses a primary (radio side) of 3t and secondary of 24t. Last update: 17th September, 2015, 8:43 AM

Transmit performance of 2m hand held transceivers – absolute gain estimates

Transmit performance of 2m hand held transceivers reported relative field strength measurements for some transceiver / antenna combinations. This article documents a more careful measurement of the absolute field strength of one combination, and application of that knowledge to the other results. Measurements of field strength were done with Lou Destefano’s (VK3AQZ) VK3AQZ RF power meter … Continue reading Transmit performance of 2m hand held transceivers – absolute gain estimates