Installation guide

Planning and Designing RIO Cable System
890 USE 101 00 October 2006 61
Planning RIO Drops
Overview The maximum length for Modicon’s recommended drop cable is 164 ft (50 m).
Keeping the drop cable lengths within this limit helps reduce attenuation on the drop
and noise problems on the system. The minimum length for a drop cable is 8.53 ft
(2.5 m)—shorter drop cable generates unacceptable signal reflections from the tap.
RG-6 is the more commonly used drop cable—it has fair noise immunity and good
flexibility. RG-11 cable can also be used—it has better noise immunity and lower
loss; RG-11 is recommended in high noise environments.
Connecting the
Drop Cable to the
Drop Adapter
All drop adapters connect to a coaxial drop cable via either an F connector or a BNC
connector:
*The older J890/J892-00X adapters use a BNC connector and require a 75 Ω inline
terminator in drop cable.
Each drop adapter must be connected separately to a tap port. The tap isolates the
drop from other drops on the network and also from the trunk cable. Multiple
adapters cannot be connected on the same port of a tap. Since an adapter is not
directly connected to any other node on the network, most installation and noise-
related problems at a drop will not reflect across the entire RIO system.
RIO drop adapters cannot be connected directly to the trunk; they must be
connected to a drop cable that is connected to a tap. Direct connection of adapters
will cause a severe trunk impedance mismatch.
Minimizing Low
Receive Signal
Level Problems
Some RIO processing devices have a dynamic range of +0 dBmV to +35 dBmV for
receiving signals. Any signal below +0 dBmV cannot be received. No indication will
be given that the signal is too low, but signal levels that vary above and below this
figure will exhibit an increased bit error rate. (This is why the attenuation between
any two nodes must not exceed 32 ... 35 dB.)
RIO Adapter RIO Cable Connection Drop Termination
J890/J892-00x BNC Connector External
J890/J892-10x* BNC Connector or F Connector(s) In the drop adapter
ASP890300 F Connector(s) In the drop adapter
P890/P892
P451/P453
140CRA93100/93200
This document provided by Barr-Thorp Electric Co., Inc. 800-473-9123 www.barr-thorp.com