FT37-43 for a 49:1 EFHW transformer enquiry

A correspondent asked whether Sontheimer coupler – transformer issues – an alternative design – FT37-43 could be used to inform design of a 49:1 EFHW transformer based on the same core, but with a 2 or 3t primary. In the case of the Sontheimer coupler the winding with the higher number of turns appears in … Continue reading FT37-43 for a 49:1 EFHW transformer enquiry

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 – #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: 27th May, 2022, 6:28 PM

Another small efficient matching transformer for an EFHW – 2643251002 – #2 – prototype bench measurement

The article Another small efficient matching transformer for an EFHW – 2643251002 – #1 – design workup lays out the first steps in a design. This article documents bench measurements of a prototype transformer. Above is the prototype transformer wound with 14t of 0.71mm ECW tapped at 2t. The mm rule gives some scale. The … Continue reading Another small efficient matching transformer for an EFHW – 2643251002 – #2 – prototype bench measurement

Another small efficient matching transformer for an EFHW – 2643251002 – #1 – design workup

The article Another small efficient matching transformer for an EFHW – 2643251002 described a correspondent’s , Luis, CT2FZI, implementation of the transformer. I have also had lengthy discussions with Faraaz, VK4JJ, who is experimenting with a similar transformer. This article describes my own design workup and measurements using a Fair-rite suppression core, 2643251002. The cores … Continue reading Another small efficient matching transformer for an EFHW – 2643251002 – #1 – design workup