For the Big Ten Network, try 462.1375. I've heard this used at Illini volleyball, softball, and soccer games that the Big Ten Network covered. Very little radio traffic on there though as it appears the camera men use a wired system or something else that I have not been able to monitor.
Here's more info about the Big Ten Network communications that I've been able to hear:
Big Ten Network - The RadioReference Wiki
I'd be interested as to what university freqs/talkgroups that are good to monitor during Purdue games.