The antenna is will be mounted on a flat roof that is 50ft up with a 10ft mast. Should i also install a rotator? I if i dont do the rotator which way should i face the loop?
Normally one faces the loop towards a localized source of interference to null it out. The null is very low to the horizon in a figure-8 pattern. From above, there is very little null, so the loop is mostly considered omnidirectional for skywave propagation. Careful listening might reveal that there is actually a somewhat oblong skywave pattern above, rather than purely omni.
That is, if you look through it like holding a magnifying glass in your hands, the null will be broadside to the loop. This null is very sharp - a few degrees either way and you'll hear the noise - so most install a rotator, or use the "strong-arm" method if they aren't battling many noise sources.
The small aperture loop does not need to be very high above ground to work properly - although getting it above the roof may physically get it farther away from local noise sources reducing the need for critical rotating.
These loops also depend on extreme electrical balance to give you a bi-directional null down low. You should be able to rotate the loop through nearly 360 degrees, and observe two identical nulls on local noise as your rotate it fully around. If you only obtain one null, or some weird cardioid type pattern when nulling, that means that there is an electrical unbalance somewhere.
If suffering from unbalance, make sure the loop is as far away from other nearby metallic structures, or even hidden ones like chicken-wire inside walls, etc. Mount it in another location, and rotate through 360 degrees again to make sure you can obtain a null on both "sides" of the loop.
In extreme cases of unbalance, where you can barely detect a nulling effect at all, check to make sure that your feedline hasn't taken over as the antenna - typically the coax braid - turning your nice loop into a random wire with a lollipop on the end. Lose a conductor, or have a very-high resistance contact somewhere at the loop can do this - periodic maintenance is a must. Other methods to reduce "common mode" problems like rf-chokes may need to be placed on the feedline.
That being said, while an exact balance is desired, it is not absolutely necessary if the null that you do obtain does the job!
