Here's a follow-up in trying to get OTA in my upcoming La Habra Heights, CA 90631 home which is in a difficult area.
Finally, I got a RCA ANT751R antenna in the ground level's kitchen facing the opened screen patio. The assembled antenna part (did not attach the holder part) sat on a high chair for testing facing North direction with the big hill/small mountain in the way. It actually worked decently depending on the directions (N or NW; left or east of the neighbor's big house and their backyard's small mountain/giant hill across the street). The portable ATSC DTV was able to pick up from 70 to 103 channels (it varies a lot depending on what directions and stable the signals are). It got annoying when it kept losing channels like KCBS2, KNBC4, KCAL9, KTTV11, KCOP13, etc.
For examples: (N)orth (right side of the neighbor's house) seems to do well with these most wanted channels: KNBC4 and KSCI/LA18. NW (left side of the neighbor's house) seems to do well with these most wanted channels: KCBS2, KABC7, and 62 (unstable). Other channels seem to be OK (forgot to record their antenna directions): KTLA5, KCOP/UPN13, KOCE50, and KLCS58. We have not put this new antenna in the attic yet facing the north direction and side in the house, but I am hoping it will do better than on the ground level.
Also, we tried a powered Philips Digital Indoor TV antenna SDV7225T/27 (big rectangular dish + a single pole rabbit ear antenna facing to the right horizontally in NE direction) which did better than a single pole rabbit ear aneanna. Its results were various depending on directrions and close to the kitchen patio door screen (glass window opened):
Adjacent to the kitchen screen door and holding this antenna above 5' from the floor/ground with wanted channels:
KNBC4 (unstable), KABC7, KCAL9, KTTV11, KCOP13, KSCI/LA18, KCET28, and 62 (unstable).
A few inches behind the kitchen screen door on a high chair with these wanted channels:
4 (N; unstable), 7 (NW), 9 (NW), 11 (N and NW), 13 (NW), 28 (N), 50 (N, unstable), 58 (unstable), 62 (unstable),
FYI, my parents refused to get a roof-top antenna since they said it was too big, complex, and ugly, and didn't want to get someone on the roof to install. However, they were OK with this indoor attic antenna.
We'll try more later. Hopefully, the attic will be good!