End Fed Half Wave matching transformer – 80-20m

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

End fed half wave matching – voltage rating of compensation capacitors

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

End Fed Half Wave / Inverted L / Half Wave Dipole

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 (0.005,13): 10m; lossless balun / matching device. Key differences: ground connection: Inverted L = … Continue reading End Fed Half Wave / Inverted L / Half Wave Dipole

The magic of End Fed Half Waves (EFHW)

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 End Fed Half Waves (EFHW)

Line loss under standing waves – recommendation of dodgy tool on eHam

In a discussion about using a 40m centre fed half wave dipole on 80m, the matter of feed line loss came up and online expert KM1H offered: Use this to help make up your mind. Add it to the normal coax loss. http://www.csgnetwork.com/vswrlosscalc.html This is to suggest that the feed line loss under standing waves … Continue reading Line loss under standing waves – recommendation of dodgy tool on eHam

80m half wave dipole made from 0.91mm steel MIG wire

Hams being innovative come up with a myriad of cheap alternatives for wire for antennas. One of those alternatives is common 0.91mm steel MIG wire. Steel MIG wire is often coated with copper and is claimed by some online experts to “work real good”, particularly as a stealth antenna. But is it the makings of … Continue reading 80m half wave dipole made from 0.91mm steel MIG wire

End fed matching – design review

A correspondent asked me to review an end fed matching unit that uses a FT82-43 ferrite transformer to transform the high impedance of a 40m end fed half wave down to approximately 50+j0Ω. His design uses a primary (radio side) of 3t and secondary of 24t. Last update: 17th September, 2015, 8:43 AM

End fed wires – another matching case study

A reader of my article End fed wires – new hams love ‘em asked about the performance of the matching transformer described at (Osborne 2014). (Osborne 2014) gives the transformer design above using a FT82-43 ferrite toroid with three turns on the primary. The concept is to adjust the antenna length and C1 for a … Continue reading End fed wires – another matching case study