Designing with ferrite binocular cores can be frustrating as there are different formats in which data is provided, and data for different mixes on the same dimensioned cores appear inconsistent. #61 mix This article documents calculated geometry Σ(A/l) derived for a number of Fair-rite cores from their specified Al (at µi). Last update: 27th August, … Continue reading Designing with binocular ferrite cores – Σ(A/l)
Ferrite cored inductors and transformers saturate at relatively low magnetising force. #61 material example Lets work through an example of a FT50-61 core with 10t primary at 3.5MHz. Magnetic saturation is one limit on power handling capacity of such a transformer, and likely the most significant one for very low loss cores (#61 material losses … Continue reading RF transformer design with ferrite cores – saturation calcs
A review of transformer design In a process of designing a transformer, we often start with an approximate low frequency equivalent circuit. “Low frequency” is a relative term, it means at frequencies where each winding current phase is uniform, and the effects of distributed capacitance are insignificant. Above is a commonly used low frequency equivalent … Continue reading RF transformer design with ferrite cores – initial steps
Commercial products often have power ratings that bear checking. There are common some key properties that are relevant: where loss is high, core loss tends to dominate; the specific heat of ferrite is typically quite high; the capacity to dissipate heat is related to many factors. Last update: 16th June, 2019, 9:26 AM
The article Estimating the Insertion VSWR in a ferrite cored RF transformer discussed the importance of sufficient magnetising impedance to InsertionVSWR at low frequencies. Above is a low frequency equivalent circuit of a transformer. Although most accurate at low frequencies, it is still useful for RF transformers but realise that it does not include the … Continue reading High end VSWR compensation in a ferrite cored RF transformer
The article Estimating the magnetising or core loss in a ferrite cored RF transformer discussed a first cut approach to determining the minimum magnetising impedance from a core loss viewpoint. This article considers the effect of magnetising impedance on VSWR. For medium to high µ cored RF transformers, flux leakage should be fairly low and … Continue reading Estimating the Insertion VSWR in a ferrite cored RF transformer
The article End fed matching – design review and many later ones set out a method of estimating the magnetising or core loss in a ferrite cored RF transformer (such as often used with EFHW antennas). There are two elements that are critical to efficient near ideal impedance transformation over a wide frequency range, low … Continue reading Estimating the magnetising or core loss in a ferrite cored RF transformer
Designing with some common Fair-rite binocular ferrite cores can be frustrating because different parameters are published for different material types, and some are controlled for different parameters. An approach is to derive the key geometry parameter from the published impedance curves and published material complex permeability curves. For example, the above curves for a 2843002402 … Continue reading Geometry factors for some common Fair-rite binocular ferrite cores
I have progressively added some further materials to Ferrite permeability interpolations calculator. Of interest to European designers is inclusion of three common materials used for HF applications, Ferroxcube’s 4A11, 4B2, and 4C65. Last update: 22nd September, 2018, 7:27 AM
At Feasibility study – loop in ground for rx only on low HF – small broadband RF transformer using medium µ ferrite core for receiving use – 50:200Ω I laid out a design using Fair-rite a #43 ferrite smallish binocular core. #43 is a medium permeability NiZn ferrite. I have been asked by several correspondents … Continue reading Feasibility study – loop in ground for rx only on low HF – small broadband RF transformer – discussion of ferrite material choice