Is Cat5 (or Cat6) cable length doubled when using a power injector ?

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May 3rd, 2012
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Hi everyone,

Let's say I have a 100m cable running from a standard switch to a power injector (namely AIR-PWRINJ4).  Do I have another 100m from the injector to the access point ?

Thanks in advanced.


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andreperron Thu, 05/03/2012 - 11:18
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Hello Steve,

Thanks for that fast response !

So you mean I am limited to 100m between the switch and the access point, no matter where in the chain is the injector ?  So if I place the injector right in the middle of the cable run, I will have 50m on each side and no more ?...

So the only way would be to use a PoE switch instead of the injector, right ?



Stephen Rodriguez Thu, 05/03/2012 - 11:19
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or a hub.  if you put any switch/hub at 100M, you would then have another 100M from that point.


Edwin Summers Thu, 05/03/2012 - 12:11
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Sorry to intrude, but just wanted to offer...  Regardless of whether or not you use a power injector, the Ethernet standard limits the distance of a single Ethernet run to 100m.  It's either an issue of signal loss, dispersion, bit timing, or a combination of all.

While having a switch would grant you another span, your injector would still be limited to the last span's 100m because the power will not flow through the switch (adding the switch won't give you 200m for your PoE).

Hope I didn't confuse the issue. -Ed

Leo Laohoo Thu, 05/03/2012 - 15:09
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Just how long do you want?

If it goes beyond 100 metres the force the interface down to 10 Mbps.


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