Collinear antenna - reflector

[Terrorr]

Hello, I have collinear antenna mounted at my balcony. Did someone test additional reflector in this kind of antenna ?

[Kvisko]

I was under impression that if you add a reflector from any side, that the collinear antenna should by definition become directional antenna of some kind. Like corner antenna for example. Also, adding anything under it can change the direction of the waves towards the horizon. I am not an expert but there are many good resources about that on the web. For example ARRL or other ham radio would be my first try/choice.