As always, do choose the right tool for the job. 75176 chips are for 32 nodes and nobody will take the blame if your data are lost on an overloaded network.
As shown on a previous post there are more recent chips that do 256 nodes. Price is very good, so why challenge your luck?
If you insist on using the ancient (but reliable I have to admit) 75176 then do place a repeater after 30 nodes an extentd the network another 30 nodes and 1200 meters. I would place a dedicated chip for transmit and another one for receiver, forgeting the auto switch between the Tx/Rx lines. You are going to place a UTP/FTP cable, so there are free pairs to use as dedicated Rx/Tx lines.
Ioannis
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