For a loop antenna, polarization is determined by the location of the open end of the loop; having the
open end at the top or bottom results in horizontal polarization, while having the open end at either side
results in vertical polarization. Since television signals have horizontal polarization and most people
will not mount the antenna on the ceiling, this pretty much means the open end of the loop needs to be
at the bottom.
To induce currents in the loop and provide the signal to the receiver, the sides of the loop must be
separated as seen from the transmission source (needs some amount of horizontal length at the top).
If the loop is turned "edge-on" to the signal source, only minimal current will be induced and much less
signal will be provided; turning the loop to be perpendicular to (facing) the signal source provides the
maximum signal.
Tilting the loop up and down has only a relatively small effect on the received signal compared with
turning the loop. It is still best if the loop is tilted to be perpendicular to the signal source.