Reviewing consistency of measured and model data, the first posting was based on an incorrect model parameter (aol), the article is now revised for the correct value, apologies. End Fed Half Wave matching transformer – 80-20m described a EFHW transformer design with taps for nominal 1:36, 49, and 64 impedance ratios. Keep in mind that … Continue reading End Fed Half Wave matching transformer – 80-20m – model and measurement
A reader of End Fed Half Wave matching transformer – 80-20m asked if a good transformer could be made with with a FT114-43 core. The original transformer above comprised a 32t of 0.65mm enamelled copper winding on a FT240-43 ferrite core, tapped at 4t to be used as an autotransformer to step down a load … Continue reading End Fed Half Wave matching transformer – 80-20m – LO1238 variant
A reader of End Fed Half Wave matching transformer – 80-20m asked if a better transformer could be made with a stack of 2 x FT240-43 cores and using half the turns. The original transformer above comprised a 32t of 0.65mm enamelled copper winding on a FT240-43 ferrite core, tapped at 4t to be used … Continue reading End Fed Half Wave matching transformer – 80-20m – 2xFT240-43 variant
A prototype broadband transformer for a End Fed Half Wave operated at fundamental and first, second, and third harmonic is presented. The transformer comprises a 32t of 0.65mm enamelled copper winding on a FT240-43 ferrite core, tapped at 4t to be used as an autotransformer to step down a load impedance of around 3300Ω to … Continue reading End Fed Half Wave matching transformer – 80-20m
The so-called End Fed Half Wave antenna system has become more popular, particularly in the form of a broadband matching transformer in combination with a wire operated harmonically over perhaps three octaves (eg 7, 14, 21, 28MHz). The broadband transformer commonly uses a medium µ ferrite toroid core, and a turns ratio of around 8:1. … Continue reading End fed half wave matching – voltage rating of compensation capacitors
Introduction End Fed Half Wave antennas are again very fashionable with hams, accompanied by extraordinary claims and somewhat sparse understanding (the way of modern ham radio). To add some light I have created a set of NEC 4.2 models of a half wave antenna on 20m to give some insight into the behaviour of a … Continue reading End fed half wave – NEC models for 20m
The popular End Fed Half Wave is all things to all men, but this article compares an End Fed Half Wave, Inverted L, and Half Wave Dipole with some common parameters: frequency: 7.1MHz; flat top length: 20m; Height above ‘average’ ground (σ=0.005, εr=13): 10m; lossless balun / matching device. Key differences: ground connection: Inverted L … Continue reading End Fed Half Wave / Inverted L / Half Wave Dipole
I have noted recently the increasing popularity of the so-called End Fed Half Wave antenna, though the term often includes harmonic operation of the antenna. It seems that at the heart of common ham understanding of this antenna system is that some kind of two terminal feed device creates a scenario with current on the … Continue reading The magic of the End Fed Half Wave antenna / EFHW
A chap asked online for dimensions of a 50MHz dipole with a feed point of 200+j0 to suit 50Ω feed line and a 1:4 coax half wave balun. The “+/- 0j” is hammy Sammy talk from an ‘Extra’. This type of balun, properly implemented, is a good voltage balun, and it is quite suited to … Continue reading Center-Fed Dipole : elements length for a Z=200 +/- 0j ohms
A correspondent wrote asking about the design of a matching network for a Half Square antenna for 80m, voltage fed at one end. Above is the current distribution on the half square voltage fed. It is essentially two in-phase vertical quarter waves separated a half wavelength, a broadside array. Feed point impedance at resonance is … Continue reading 80m voltage fed Half Square matching workup