Sooo..correct me if I'm wrong, the antennas on solo (the controller and the bird) are vertically polarized? So if I upgrade the units on the controller for something similar just a little higher gain I need the vertically polarized units,correct?
I am by no means an expert, but polarization of a signal is not only a property of the antenna design and construction (and ultimately the electric field generated by the antenna), but it is also affected by the antenna's physical orientation in space. Solo's antennas are whip antennas - held roughly vertically in the legs and if following instructions, roughly vertically on the controller. This maintains the roughly vertical polarization on both ends.
Signal reception degrades as you lose polarization, with "a loss of 20 or more dB at 90 degrees" (e.g. pairing a horizontal and vertical antenna held in space at exactly right angles to each other). This is why matching polarization is a simple way to maximize your signal strength.
A problem for us, is that Solo is moving around - rocking the antennas as we accelerate and decelerate while flying. We also are moving the controller in our hands. This will cause shifts in the signals, making reception less than ideal. Not a big deal if Solo is close by. But in some cases, if you're at your range limit, it's enough to contribute to you losing connection completely.
In satellite communications, the movement of the satellite also causes issues with signal reception. Circular polarization (CP) has been used to overcome some of these issues. Others have used CP antennas in FPV applications with success. The FPVLR, among others (cloverleaf, skew planar etc.) is a CP antenna by design.
Depending on the construction of the antenna, the circular polarization may or may not be near perfect. You can get almost linear or even elliptical radiation patterns and anything in between. When it comes to measuring how well the antenna maintains it's circular polarization, they use the "axial ratio" to measure this property. Using 2 antennas with excellent circular polarization will theoretically get you better results.
Here's a couple links I found that might help:
http://www.radio-electronics.com/info/antennas/basics/polarisation-polarization.php
http://www.astronwireless.com/topic-archives-antennas-polarization.asp