Alexis here are 2 overlays for the Sirio 827 with 4 x 9' foot radials (Red) vs. 8 x 55'' inch radials (Blue).
The active model has an (*) beside the title below the word Primary at the upper left corner of the page.
I think the most important differences I see between my 2 models of the Sirio 827, is the increased maximum gain close to the horizon...as compared in the overlays images in the PDF file below.
See the green dot cursor for maximum gain and angle for each model.
827 with 8 x 55" radials
4.41 dbi gain at 8* degrees above the horizon
827 with 4 x 9' radials
3.66 dbi gain at 41* degrees above the horizon
IMO, this considerable difference indicates that the 4 x 9' foot radials tend to push the high angle lobe up higher, and thus putting less gain at or near the horizon where it is more desirable.
Alexis, there are several old discussions at the top of the CB Antenna section. "Sticky Threads," talking about Sirio using CST, a superior modeling program to maximize their antenna designs. In particular their New Vector 5000 is discussed.
If this story is true, and Sirio modeled their 827, and seeing similar differences as I did above using Eznec 5, then I would doubt very seriously Sirio had any questions in choosing to use the shorter radials on their premire 5/8 wave antenna.
To me, these overlays show the improved gain effects due this pattern compression effect when using 8 x 55" radials rather than 4 full 1/4 wave radials.
