Specifications

14
As mentioned before, the maximum CAT-5 UTP cable length between two network devices—that is, between any
RAVE unit, hub, etc., and any other—is 100 meters, or 328 feet. You can cover longer distances by using optical
fiber, as mentioned earlier, or by running 100-meter lengths of UTP cable linked by Fast Ethernet hubs. The latter
solution is practical mainly if you need, or are likely to need, RAVE units at the intermediate points, and it is possible
only if you actually have power sources for all the Fast Ethernet hubs. Ultimately, the cumulative round-trip propagation
delays of all the cables (typically 1.112 bit periods/meter) and intervening hubs (Class I hub:
<140 bit periods;
Class II hub:
<92 bit periods; QSC FE hub: <46 bit periods) imposes a limit on how far you can carry this sort of
configuration. See the CobraNet network guidelines at the Peak Audio web site (cited above) for further guidance,
especially if you are designing a CobraNet network whose span approaches or even exceeds 1000 meters.
A fiber optic run of typical 62.5 µm multimode fiber can be up to 2 kilometers, or 6560 feet or 1.24 mile. Single-
mode fiber, a much higher grade, offers better data pulse integrity but exhibits the same amount of delay as
multimode. Therefore, it is not bound to a 2 km limit, but you must still consider its effect on total delay.
Although a RAVE network has a capacity of 64 audio channels—i.e., eight network channels, each with eight
audio channels—there is no set
limit to the number of receivers
that a RAVE network will support,
except that as you add more hubs
and cabling, the data delays will
increase.
This table shows the propaga-
tion delay in various devices and
media used in a CobraNet net-
work. Three different types of
media converters are shown here,
which should give you an idea of
the wide range of performance
parameters even among devices
with similar functions. When cal-
culating the maximum system
span, you must add up all the delays involved, in cabling, hubs, converters, and the RAVE units themselves.
For example, a 100-meter length of CAT-5 cable means a delay of 111.2 bit periods, and a Class I hub will have
up to 140 bit periods of propagation delay. A Class II hub has a better level of performance, so the delay is shorter.
The maximum span of a CobraNet network is 2560 bit periods, and as long as the sum of the propagation delays
from any one RAVE device to any other RAVE device is less than that amount, the network will operate properly
(if all other conditions are satisfactory, such as individual segment lengths being within limits).
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If you exceed the maxi-
mum network diameter,
CobraNet communication
might not function reliably.
In extreme cases, the net-
work will simply stop func-
tioning; more often, though,
it will pass audio but also
have noticeable artifacts,
such as clicks.