You may not be able to decipher what a "75 left, wide 35, y cross" is but I've found that most of the conversation is in plain English. You hear discussions similar to "the safety freezes up every time the halfback pulls right, so run the wide receiver on post left, faking a run right", or "the linebacker is being held on every pass play by the left tackle, let the ref know, we can't go on all night like this" and the like. Quite often the press box observers are not familiar enough with the specific plays to name them as the offensive coaches are down on the field. I've attended games where I have an earplug on and began telling those with me what the next play will look like, then had others around me ask if I could please speak up so they could hear me also.
For high school games I've found just about everything being used, not only business frequencies, but sometimes a school maintenance frequency that is licensed for wide itinerant use. Sometimes it isn't licensed. It is hard to find the frequencies most of the time because they often speak very briefly. I've even gone to college games in the San Francisco Bay area and picked up more than one game at a time and could not figure out which frequency went to what game for quite some time.
One thing for sure, it is getting more and more difficult to pick up these devices due to the different technologies being employed. I assume that there was eavesdropping by opposing teams.
