July 8, 2008
A frequent question I see is “what is the maximum cable length for xxx type of cable?”
Unluckily this is a huge variable. One cable length may work fine in one instance, but terrible in another. Factors such as the quality of the cable, EMF, quality of the connectors, how many bends are in the cable, quality of the components it’s connecting, even electrical storms, local magnetic fields, and sun spots can have a huge affect.
However there is a maximum limit to most cable types by design. Below are a list of the most common ones.
Maximum lengths of common cable types:
DVI: 5 meters, or 15 feet is the recommended length. High quality cables can increase this distance up to 50 feet, with 40 feet being a common number.
Ethernet: Ethernet cable has a hard limit of 100 meters. Due to the way packets are sent, even good quality cable will not be able to increase this. On the other hand in this day and age, except in big business buildings, 300 feet is more then most anyone needs.
Firewire: 4.5 meters or about 13 feet. Firewire is one of the pickier specifications, with out an extender (and even then it can only be extend 30 feet maximum) going past this length is asking for problems to come up.
USB: 16 Feet or just over two meters. A wide variety of USB Extenders can be purchased to increase that up to 150 feet. In actual use though, for low signal situations such as data cables for cameras, or USB keyboards, 25 feet is usually doable without an extender. Past that you’re going to have issues.
Note: These numbers are based on the specification’s maximum length. Extenders of all types exist, and again, good quality cable with no EMF interference can and does make a big difference.