With the LL50A and UTAdvanced, can I perform RS-485 communications without a dedicated cable?

Yes, if using a UTAdvanced series instrument with the RS-485 communication option. Set the RS-485 protocol on the main unit to 8 (MBRTU: Modbus RTU). The initial value is 8. Select RS-485 in the LL50A communication execution screen, and make the communication conditions and addresses the same as on the main unit.