Rockwell Automation 1786-series ControlNet Coax Media Planning and Installation Guide - Manual (Page 24)

24 Publication CNET-IN002B-EN-P - June 2010
Chapter 2 Plan a ControlNet Coax Media System
EXAMPLE
If your segment requires 10 taps, the maximum segment
length is:
1000 m (3280 ft) - 16.3 m (53.4 ft) x [10 - 2]
1000 m (3280 ft) - 130.4 m (427.7 ft) = 869.6 m (2852.3 ft)
Although you can use high-flex RG-6 cable
(catalog number 1786-RG6F) in your system, the amount
of cable you can use is less than the amount of standard
RG-6 cable that can be used. You should keep the amount
of high-flex RG-6 cable use to a minimum. Use BNC bullet
connectors to isolate areas that require high-flex RG-6
cable from areas that require standard RG-6 cable; this
allows the high-flex RG-6 section to be replaced before
flexture life is exceeded.
You can determine the allowable total length of
high-flex RG-6 cable in your application by using the
equation below. Each additional tap decreases the
maximum length of a segment. The maximum number of
taps allowed on a segment is 48.
Cable attenuation is defined as the signal loss measured at
10 MHz per 1000 ft (304 m) of cable. Cable attenuation is
listed in the ControlNet Standard and High-flex Coax
Cable Installation Instructions, publication
1786-IN009 .
Using the formula described above, if your segment
requires three taps using 1786-RG6F cable, which has an
attenuation of 13.5 dB, the maximum segment length is:
[(20.29 db - 3*.32 db) / 13.5 db] * 304
(19.33 db / 13.5 db) * 304 = 435.2 m (1427.8 ft)
The total trunk-cable length or number of taps can be
increased by installing repeaters on the segment. This
creates another segment.
Max allowable segment length of high-flex cable =
(20.29 db - number of taps in segment * .32 db)
Cable attenuation @ 10 MHz per 304 m (1000 ft)