A new impedance calculator for RF inductors on ferrite cores

Some time ago I published a calculator for estimating the impedance of RF inductors on toroidal ferrite cores (Calculate ferrite cored inductor). The calculator (input form above) use the core dimensions and complex permeability as the basis for calculation. There are some popular cores that are not simple toroids and so not suitable for direct … Continue reading A new impedance calculator for RF inductors on ferrite cores

Accuracy of AIMuhf system – AIM865A vs AIM882 on a ferrite cored inductor

In other posts, I have commented on the apparent inconsistency of AIMuhf measurements. One of the devices I often wish to measure is a ferrite cored choke such as those used for a Guanella 1:1 balun. A small test inductor was made to provide a common device for measurement across instruments, and versions of software, … Continue reading Accuracy of AIMuhf system – AIM865A vs AIM882 on a ferrite cored inductor

Sevick’s comments on selection of ferrite mix

(Sevick 2001) discusses efficiency of transmission line transformers that use nickel-zinc ferrites in Chapter 11 “Materials and power ratings” applied to broad band baluns. In Chapter 11 he reports a range of measurements of two different basic configurations, a 4:1 Ruthroff balun and a 4:1 autotransformer and uses nickel zinc ferrite cores of types that … Continue reading Sevick’s comments on selection of ferrite mix

Attempting to reconcile W5DXP & G3TXQ’s comparison of K and 52 mix ferrites

Steve (G3TXQ) posted a graph comparing Cecil’s (W5DXP) measurements of two turns on FT240-52 and FT240-K. It is interesting to reconcile the #52 curves with Fairrite’s datasheets. A simple reconciliation is to compare results at the frequency where µ’ and µ” curves cross over. Last update: 12th October, 2015, 8:50 AM

Ferrite K mix

Among forum experts, there are ready recommendations for the ideal ferrite material (or mix) for a balun, often without knowing any detail of the application. The ‘magic’ mixes include K. Perhaps they are devotees of Sevick. Over some years I have searched for manufacturer’s data on K mix, and found only two references: Amidon who … Continue reading Ferrite K mix

nanoVNA – evaluation of a voltage balun – RAK BL-50A

In this article, I will outline an evaluation of a ‘classic’ voltage balun, the 1:1 RAK BL-50A voltage balun, specified for 1.8-30MHz. These were very popular at one time, but good voltage baluns achieve good current balance ONLY on very symmetric loads and so are not well suited to most wire antennas. Above is a … Continue reading nanoVNA – evaluation of a voltage balun – RAK BL-50A

Measurement of recent ‘FT240-43’ core parameters

This article reports measurement of two ‘FT240-43’ cores (actually Fair-rite 5943003801 ‘inductive’ toroids, ie not suppression product) purchased together around 2019, so quite likely from the same manufacturing batch. IIRC, the country of origin was given as China, it is so for product ordered today from element14. The measurements are of 1t on the core, … Continue reading Measurement of recent ‘FT240-43’ core parameters

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

(How) does this balun work?

I was sent a pic of a balun and asked to explain how it works. With no other detail than the pic, it is difficult to supply a complete answer. Nevertheless, an analysis of what is presented follows. Last update: 6th November, 2020, 5:39 PM