Installation guide

Planning and Designing RIO Cable System
890 USE 101 00 October 2006 53
Calculating
Maximum
System
Attenuation
To calculate maximum attenuation, add all sources of attenuation between the RIO
head processor and a drop adapter; the total loss must not exceed 35 dB (32 dB for
controllers without pre-amps). The maximum attenuation for the system is generally
measured from the RIO processor node to the last drop adapter on the network. The
last adapter usually represents the maximum loss of the entire cable system. There
are exceptions however—adapters near the end of the cable system with long drop
cables may have greater attenuation.
Maximum system attenuation at 1.544 MHz can be calculated as follows:
dB loss = TCA + DCA + TDA + (NOS x 6) + (NOT x 0.8)
where:
z TCA = the trunk cable attenuation from the head to the end of the trunk
z DCA = the drop cable attenuation, generally at the last drop
z TDA = 14 dB, the tap drop attenuation
z NOS = the number of splitters in the system
z NOT = the number of taps between the last node and the head
Note: On a network using dual or redundant trunk cables, calculate attenuation on
each separately. Each trunk on a dual or redundant RIO network can handle
attenuation up to 35 dB (or 32 dB).
Note: Use (NOS x 3.5) if MA-0331-000 is to be installed. See Splitter
Specifications, p. 76.
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com