Half Square Antennas

 I have had half square antennas on 80, 40 and 20 meters. In all cases the top wire (spacing) was one-half  wave length long on the band I built it for. The half square is not a multiband antenna. My results were that the 80 meter antenna was the best antenna I ever had ( except maybe my full size 4 element 20 meter monobander)! The top wire was at about 60 feet or so. On 40 meters the Half Square antenna worked but not nearly as well as my 40 meter dipole in that it seemed to have the same gain in Europe but a more narrow pattern resulting in deeper nulls of the side than the dipole which was at about 35 feet. On 20 meters any full size (halfwave) dipole or end fed is hands down at least an S unit better if it is a halfwave (32 feet) or more high! I model a lot with EZNEC and the EZNEC results were almost exactly what I saw in practice. Any dipole or halfwave wire will have a gain of about 8 dBi if anywhere near a halfwave high. Any vertical over real earth will have maybe 0 dBi gain. In other words the dipole is at least an S unit (6 dB) better, probably 8 or more dB better. The pseudo Brewster angle can really decrease the verticals so called low angle radiation pattern. The type of ground is really critical. Salt water can pretty much make the vertical as good for DX as a high dipole. 

The reason the 80 meter half square was so good was that a dipole on 80 needs to be 130 foot up to have the 8dB gain that a 20 meter dipole has at 32 feet! The verticals have the same gain on 80 or 20, but a low dipole on 80 has very little gain at low angle, in fact the gain is negative at low angles if the 80 meter dipole is only 40 foot high.  The peak radiation angle of any horizontal antenna depends only on height above the ground. On 40 meters, if you can’t get very high with the dipole then the half square has a definite advantage as it does not have to be high to have maybe 5 dBi gain. I now use multiple half wave dipoles on 20 and higher bands so that I can take advantage of the 8dBi broadside gain! Switching from one to the other reminde me of rotating my Yagi except with a switch it is instant “rotation”!