I live in a concrete-and-steel highrise building. Various SW websites
advise that I could make an antenna made of "a few yards" of simple
insulated copper wire and hang it out of the window to improve
reception.

I've made one accordingly. The portion outside the window measures 3
yards in length and is pointing vertically down alongside the outer wall
of the building. Reception improves a bit but I'm still not getting the
stations I should be getting.

Could any SWers please let me know if:
1. my wire antenna is of the correct length; and
2. letting the wire antenna pointing vertically down alongside the outer
wall of the building is correct.