It's may not be the same for all receivers.I can get a lock at 30ish on my pansat,but I have read some say it takes a higher quality level on theirs.Some have reported getting a lock with lower levels.I have picked up a ch. before with a 20 something level and not get a lock on some with a 30 something level.I don't know how that is,but maybe some of the others can explain that.
Hope this is of some help.