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

Mornhinweg ferrite core measurements – #61

Further to Amidon’s method of rating ferrite inductors and transformers, this article discusses some interesting measurements of ferrite toroids by Manfred Mornhinweg (Mornhinweg 2019). Mornhinweg ferrite core measurements – #31 discussed his measurements of a #31 suppression sleeve. Above are his measurements of a FB-61-6873 sleeve. Essentially there are two measurements at each frequency, and … Continue reading Mornhinweg ferrite core measurements – #61

Black body emissivity of ferrite core material

Some of my articles have contained thermal pictures of ferrite cored inductors and transformers. I have been asked several times recently about the assumed emissivity and the accuracy questioned, I assume this has been discussed online somewhere. When first measuring ferrites with non-contact thermometers, I performed some experiments to discover whether the default emissivity ε=0.95 … Continue reading Black body emissivity of ferrite core material

Calculate ferrite cored inductor – rectangular cross section – enhancement – chamfered corners

The calculator Calculate ferrite cored inductor – rectangular cross section has until now assumed that the toroid has sharp corners. The corner treatment varies across commercial products, some are burnished which removes very little material, some have a chamfer or bevel, some are radiused. All of these treatments give rise to a very small error … Continue reading Calculate ferrite cored inductor – rectangular cross section – enhancement – chamfered corners