I am currently using this antenna:
It has a better gain than the original Sonoff antenna but not as high as another omnidirectional antenna I tested. The actual reason I chose this one is not gain but lobe… it tends to have a higher gain in the direction it is pointing and a significantly lower gain in the opposite direction. Given my coordinator is in the non ideal side-of-the-house location, I figured it might help attenuate wifi interference (wifi ch9) from my neighbor (low gain side of antenna facing their house) and increase coverage in my house. While it is hard to say whether I achieved my goal, it does seem to help. Regardless, I still get high channel usage warning messages (never know if it is referring to traffic or rf usage) and relatively frequent devices having issues.
