Robin2:
If I understand your requirement correctly there would only be a need to check for a spare channel when a new "strip" is brought into use and it would not be a problem for an nRF24 to listen for a few moments on successive channels until it finds a free channel.However, what you really need is for all three nRF24's for a single strip to find the SAME free channel, and that is not so easy.
You mention the possibility of 61 separate fencing matches simultaneously. There are only 128 different channels in an nRF24 and I'm not sure if you can use adjacent channels or if you would need to leave every second one unused. If so you would be running right at the edge of the capacity of the system.
You also need to keep in mind that WiFi and Bluetooth and micro-wave ovens also operate in the 2.4GHz band and a frequency that seems clear now may not be clear in 5 minutes time (and vice versa).
Before thinking further about this you need to provide details of how often data needs to transfer from a slave to the master. If the update rate is low then the options available will be much wider, including, for example, one master dealing with several "strips"
Another relevant question is whether there is already a commercial system that operates like this and if so, how does it work?
...R
For getting the master and the two slaves to sit on the same channel I could have the two slaves be physically connected to the master when you start or else the entire system just refuses to start. That way you can have the master find a channel and tell the two boxes to use that channel.That would also mean the slave boxes can be an identical box with the exact same hardware and software. (Makes production easier and more practical if you lose one box and not the other).
In regards to the troubles with wifi I am thinking about using RFM chips at 433MHz or 915MHz (From my understanding the RFM is very similar to the nRF in a lot of ways, correct me if I am wrong). That would allow me to not worry much about interference.
I might just have to make the entire thing search every other channel and have it be a project design that only even channels are allowed to be used.
I would need to get started on making a prototype and figure out what type of speeds I would need to be able to accurately do the lockout and buzzing.
I've talked with a few guys from Leon Paul (they currently have one of the few wireless scoring machines available out there). Although they were a bit secretive about those types of details.
I guess I just need to make a prototype box using something like the RFM then slowly start working out kinks and maybe upgrading parts if some become a limiting factor.
You've been a great deal of help! I really appreciate it.