On winding configuration of EFHW matching transformers

The net abounds with articles on broadband transformers (ie untuned) for matching End Fed Half Wave (EFHW) antennas to 50Ω. One of the aspects that is common to most designs is that the turns of the primary winding are wound ‘bifilar’ with the start of the secondary winding, indeed the twist pitch is often very short and articles often go into detail on how to make this magic thing.

The magic is that it is supposed to give closer to ideal behaviour of the transformers by way of minimising flux leakage.

The transformer above is styled on the common design, and it consists of a 2t primary and 16t secondary where the primary is wound bifilar, and a third 2t winding wound over the primary end of the transformer between the other turns. Continue reading On winding configuration of EFHW matching transformers

The sign of reactance – challenge reality check

The sign of reactance – a challenge posed a problem, a set of R,|X| data taken with an analyser of a quite simple network and asked readers to solve the sign of X over the range, ie to transform R,|X| to  R,X.

The sign of reactance – challenge solution gave a solution to the challenge, and The sign of reactance – challenge discussion provided some discussion about the problem and solution.

Some correspondents have asserted that the challenge (see above Smith chart) contains a response that is contrived for the purpose and not representative of real world antenna systems. Continue reading The sign of reactance – challenge reality check