Search Results for: ferrite

On ferrite cored RF broadband transformers and leakage inductance

By broadband transformer, I mean a transformer intended to have nearly nominal impedance transformation over a wide frequency range. That objective might be stated as a given InsertionVSWR over a given frequency range for a stated impedance. eg InsertionVSWR<2 from 3-30MHz with 3200(+j0)Ω load. These are used in many things, including medium to high power … Continue reading On ferrite cored RF broadband transformers and leakage inductance

Choosing a ferrite mix for a 160m unun rationally

One often sees people ask for help in choosing a ferrite mix for a particular application. A recent thread on social media asks for help designing a unun for the 1.8MHz amateur band, and it has provided the opportunity for participation, even if the content was not good. An important early step in designing a … Continue reading Choosing a ferrite mix for a 160m unun rationally

A simple Simsmith model for exploration of a 50Ω:200Ω transformer using a 2843009902 (BN43-7051) binocular ferrite core

EFHW-2843009902-43-2020-3-6kThis article applies the Simsmith model described at A simple Simsmith model for exploration of a common EFHW transformer design – 2t:14t to a ferrite cored 50Ω:200Ω transformer. This article models the transformer on a nominal load, being . Keep in mind that common applications of a 50Ω:200Ω transformer are not to 200Ω transformer loads, … Continue reading A simple Simsmith model for exploration of a 50Ω:200Ω transformer using a 2843009902 (BN43-7051) binocular ferrite core

Yet another ferrite toroid calculator – but is it any good?

In a recent online thread, a ‘new’ online calculator was touted:  https://miguelvaca.github.io/vk3cpu/toroid.html . References without any qualification surely imply a recommendation. In the same thread, Roger Need compared his measurement of a FT50-43 with Calculate ferrite cored inductor (from Al) (one of a set of related calculators), and Ferrite permeability interpolations. Above, his calculation reconciles … Continue reading Yet another ferrite toroid calculator – but is it any good?

Stacking two ferrite cores of different permeability for an RF inductor

One of the magic ham recipes often proposed is to stack two ferrite cores of different permeability for an RF inductor, but an explanation is rarely offered, I have not seen one. An explanation Starting with some basic magnetism… The inductance of an inductor is given by . For a closed magnetic circuit of high … Continue reading Stacking two ferrite cores of different permeability for an RF inductor

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

Ferrite cored inductors at HF – flux, loss and saturation

I see online experts opine that small signal characteristics (eg complex permeability curves) of ferrite toroids are not valid for applications such as RF common mode choke in transmitting antennas. Others opine that saturation is a practical design limit, and for example that Bs/2 is a safe / appropriate design target. Let us consider a … Continue reading Ferrite cored inductors at HF – flux, loss and saturation

Select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer – comparison of measured and predicted

Select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer – nanoVNA described a method of using a nanoVNA to select by trial possible core and turns combinations for a transformer. This article compares the results for the FT240-43 example at 3.5MHz with calculation using tools on this … Continue reading Select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer – comparison of measured and predicted

Select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer – nanoVNA – loss components graph

Select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer – nanoVNA gave an explanation of how to use a nanoVNA or the like to select a suitable core and sufficient turns for a low InsertionVSWR broad band 50Ω transformer. Last update: 1st March, 2021, 9:09 AM

Select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer – nanoVNA

This article demonstrates the use of a nanoVNA to select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer. Simple low frequency equivalent circuit Above is a very simple approximation of an ideal 1:1 transformer where the effects of flux leakage and conductor loss are ignored. A 1:n … Continue reading Select a ferrite core material and sufficient primary turns for a low InsertionVSWR 50Ω broadband RF transformer – nanoVNA