There is no hard upper limit on the number of nodes in a HumPRO Series system since the module does not store a list of connected nodes. The practical limitations are
Operating range
Channel availability
If all nodes are listening to a single master, then the limitation is the time on channel to transmit messages. Since the HumPRO Series only transmits when it has data or an acknowledgement to send, that depends on the system’s transmission activity. Only one transmitter can be active and be heard. If there are multiple systems such that they can be using different hopping patterns (logical channels), then the amount of total traffic can be higher, but less than 6 (number of hopping patterns) times as high because of occasional collisions between hopping patterns.
A system having 100 to 200 nodes all hearing one another is possible, but would only work if the aggregate data rate is low. In general, you probably can’t get over about 50% utilization, due to packet overhead and delays between transmissions. A large system could be implemented using a repeater strategy implemented by the designer.