I found this piece about EBNO it's kinda interesting. Ebno readings can commonly read from minus 3 (no signal) to plus 24 which you are unlikely to see unless you have a 30 foot dish. while a stronger signal usually means a better ebno, you can have a lower ebno due to noise/interference, signal overload/distortion etc.riding on top of that signal. as you mentioned they are the measure of signal to noise ratio so it's basically a measure of the signal strength in decibels versus the background noise level in decibels, with the added variation of actually measuring the decoded bits of data to determine if there's errors in the datastream. 6.9 would be a recommended minimum although you probably wouldn't notice any degradation in the picture til you got down to about plus 3. error correction in the receiver is filling in bad bits of data with previous good data so that you don't hear pops or see those pixel squares breaking out on the screen. between 3 and 6.9 you could consider the signal to be error correcting often and above 6.9 it would be only a few errors per hour or less.