Regarding using a 4 antenna system as mentioned in an earlier message,
would that really give me fine enough resolution to detect where a
signal was coming from within say 20 degrees? Or would it be in 90
degree increments?

YOu can go here to find one design,

http://www.qsl.net/ve2emm/pic-projec.../mtdop2-e.html

It should do around 10 degrees or so.