The Half Square antenna is basically two 1/4 wave verticals in phase and spaced a half wavelength apart on the band it is designed for.
I designed and built a voltage fed version which is as follows:
5.2m aluminium tapered tubing mounted via a fibreglass insulator on a timber pole length in my case to get the base of the vertical to the height of my shed roof.
I feed it via a Icom AH4 auto tuner at the base of the vertical however previously used a unun in which you may use a 9:1 or a 49:1 if a half wave on 40m dimensions are used.
I use the shed as the ground counterpoise however you may just use a wire between 5m - 10m long.
The horizontal wire is attached at the top of the two verticals which are separated around 10.3m apart.
You may also just use wire totally as a half wave end fed antenna and use the halt square shape format to achieve the same gains and benefits which are.
* Only 10.3m across in width so suits smaller home blocks and great for portable operation.
* Only has to be around 500mm above the ground so for a 20m version you may be under 6m in height overall yet obtain good dx performance on 20m and higher bands as well as great Australia wide strong signal coverage on 40m
* Quiet........ this antenna is the less subject to noise that I have used and experienced so if you have noisy location issues I recommend you give it a try.
I have been using this antenna design for over 8mths and if you look at my QRZ log book you will see the stations and reports I have been working with this antenna and 100 watts only and some photos of the antenna installation at my home QTH.
Greg Treble . VK3KV 2 Leurimah Crt Kalimna 0403 262 603