the original avanti patent itself tells us no less than three different times how the performance of the sigma IV can be improved but you will have to give up the reduced lateral and radial dimensions to make that happen.
i would direct you to the following pertinent sections of the patent.
https://pdfpiw.uspto.gov/.piw?docid=04282531&PageNum=1&&IDKey=&HomeUrl=http://patft.uspto.gov\
page 3, column 2, lines 47 - 66
page 4, column 4, lines 23 - 36
page 5, column 5, lines 07 - 15
as the acute angles between the "diverging" radial elements formed by the common connection point with the vertical radiator are increased, the directivity of the antenna also increases. avanti tells us in the patent that just and increase of 15 degrees (30 degrees total) can yield an increase of .5-.6 dB. and that "in some instances" directivity continues to increase as the "diverging elements" are moved even further away from the radiator.
post #661 is not from a patent or other internet document, if you want it then copy it. there is no link to it since this is the first place anywhere on the internet where this appears, i wrote it.
