Ensemble Designs 9430 Flexible Matrix Router for 3G / HD / SD / ASI - Manual (Page 31)

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Avenue 9430 Flexible Matrix Router Installation, Configuration and Operations Guide
Digital Signal Connections
The digital inputs and outputs of the Router are all equally capable of supporting 3G SDI, HD SDI,
SD SDI, DVB-ASI, SMPTE 310M and AES audio signals. Connections to sources and destinations are
made with 75 ohm coaxial cable.
Cable Length Considerations
An important technical consideration in system wiring is the length of the cables that run between
different pieces of equipment. The high frequency content of the serial digital signal, which is
attenuated in proportion to the length of the cable, sets an upper limit to the distance over which
the interface will work reliably. Beyond that distance, data bit errors will corrupt the signal and render
the content unusable. The maximum length for digital grade, RG-6 type cable (such as Belden 1694A)
varies according to the data bit-rate of the interface as follows:
Type Bit-Rate Maximum Cable Length
3G HD SDI 3 Gb/s 70 meters (229 feet)
HD SDI 1.5 Gb/s 100 meters (328 feet)
SD SDI 270 Mb/s 300 meters (984 feet)
DVB-ASI 270 Mb/s 300 meters (984 feet)
SMPTE 310M 19.3 Mb/s 100 meters (328 feet), but 30 meters (98 feet) is recommended
due to the inherent weakness of the 310M signal
AES 3 Mb/s 100 meters
These numbers are conservative in order to provide a margin of safety that accommodates variations
in the output amplitude and jitter content of sources, and the input sensitivity of destinations. Do not
exceed these values because when a system is pushed beyond its design limitations, what works one
day may not work the next day.
Furthermore, these numbers assume a direct, single cable connection between devices. If the signals
are passing through patch panels or cable couplers, the maximum total cable length must be reduced.
Fail-Safe Bypass from Input 1 to Output 1
The fail-safe bypass feature of the Avenue Flexible Matrix Router supports a connection from Input 1
to Output 1 in the event of a system or power failure. This is accomplished in a simple manner: Bypass
connects the two ports (BNC connectors) together through a passive, mechanical relay. This means
that the signal will be carried through the Router even when there is a total loss of power and control.
But it also means that the length of the cable between the source and destination is now the total of
the input and output cabling. That total must be less than the bit-rate appropriate maximum listed
in the above table. And since the Router in bypass mode is effectively a cable coupler, that maximum
needs to be further reduced. If other elements or requirements in a system design render the bypass
behavior irrelevant, this combined cable length consideration can be disregarded.
It is possible to extend performance beyond these maximums by the use of lower loss RG-11 cable
such as Belden 7732LL. The low-loss performance comes from a larger dielectric cross section, so these
alternatives are less flexible and more challenging to install and terminate.
Conversely, smaller diameter cable (Belden 1855A) is often favored for its lower weight and higher
installation density. These choices must take into account their greater high frequency attenuation.