Search Results for: Efhw transformer

A simple Simsmith model for exploration of a common EFHW transformer design – 2t:14t

This article describes a Simsmith model for an EFHW transformer using a popular design as an example. This article models the transformer on a nominal load, being . Real EFHW antennas operated at their fundamental resonance and harmonics are not that simple, so keep in mind that this level of design is but a pre-cursor … Continue reading A simple Simsmith model for exploration of a common EFHW transformer design – 2t:14t

A simple Simsmith model for exploration of a common EFHW transformer design – 2t:16t

This article describes a Simsmith model for an EFHW transformer using a popular design as an example. This article models the transformer on a nominal load, being . Real EFHW antennas operated at their fundamental resonance and harmonics are not that simple, so keep in mind that this level of design is but a pre-cursor … Continue reading A simple Simsmith model for exploration of a common EFHW transformer design – 2t:16t

Shorting winding sections of a ferrite cored EFHW transformer

A chap recently posted some advice on construction of a dual ratio transformer for EFFHW antennas, advice with an informative pic, but without measurement evidence that it works well. Pictured is a dual UnUn. I made this for experimenting. It’s both a 49 and 64 to 1 UnUn. The 49 to 1 tap uses the … Continue reading Shorting winding sections of a ferrite cored EFHW transformer

A Smith chart view of EFHW transformer compensation

I have written several articles on design of high ratio ferrite cored transformers for EFHW antennas. Having selected a candidate core, the main questions need to be answered: how many turns are sufficient for acceptable InsertionVSWR at low frequencies and core loss; and what value of shunt capacitance best compensates the effect of leakage inductance … Continue reading A Smith chart view of EFHW transformer compensation

Another small efficient matching transformer for an EFHW – 2643251002 – #5 – improved Simsmith model (v1.03)

This article applies the improved model: An improved simple Simsmith model for exploration of a common EFHW transformer designs (v1.03) to the design at Another small efficient matching transformer for an EFHW – 2643251002 – #1 – design workup. Above is the prototype transformer wound with 14t of 0.71mm ECW tapped at 2t. The mm rule … Continue reading Another small efficient matching transformer for an EFHW – 2643251002 – #5 – improved Simsmith model (v1.03)

Another small efficient matching transformer for an EFHW – 2 x 5943000601 (FT82-43) – VK4JJ build and measurement

The transformer is an autotransformer of 3+21 turns single layer close wound on a ‘stack’ of two Fair-rite 5943000601 cores (FT82-43?). Note that these were genuine Fair-rite stock, other #43 mix products in the market place may be significantly different (see Ferrite cored RF chokes in Class-E RF power amplifiers – core material issues for … Continue reading Another small efficient matching transformer for an EFHW – 2 x 5943000601 (FT82-43) – VK4JJ build and measurement

Another small efficient matching transformer for an EFHW – LO1238 – VK3PY, VK3TU build and measurement

This article documents the process of design, prototyping, measurement and final build of a 1:49 impedance ratio (1:7 turns ratio) EFHW transformer, exploring some alternative designs along the way, a collaboration between VK3PY and VK3TU with a little guidance. The transformer is wound on a Jaycar LO1238 35x21x13mm toroid of L15 material (L15 appears to … Continue reading Another small efficient matching transformer for an EFHW – LO1238 – VK3PY, VK3TU build and measurement

Another small efficient matching transformer for an EFHW – 2643251002 – #4 – G8GYW build and measurement

The article Another small efficient matching transformer for an EFHW – 2643251002 – #2 – prototype bench measurement continued the development of a transformer design. This article analyses measurements at 7.1MHz reported by Mike, G8GYW of his build of a similar transformer. Above is G8GYW’s build, that is an inch grid on the bench. Last … Continue reading Another small efficient matching transformer for an EFHW – 2643251002 – #4 – G8GYW build and measurement

Another small efficient matching transformer for an EFHW – 2643251002 – #4 – a paired Guanella 1:1 balun

Another small efficient matching transformer for an EFHW – 2643251002 – #2 – prototype bench measurement continued the development of a transformer design. This article presents a Guanella 1:1 (current) balun (or common mode choke) using the same type of core. Above, the EFHW transformer prototype. Last update: 14th April, 2024, 1:34 PM