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Power Issue

Posted: Fri Jun 27, 2008 5:31 pm
by dwill
Hi All,
I'm actually very new to this Mikrotik Radios, so i dont know if this is the right "spot" to share my problems. i just started on my own and its getting quite interesting.

My issue is i tried installing a RB133 (24v/0.36A) over a CAT6 cable running the length of 200ft/61m. the radio does not come on. the message i keep getting on my Laptop is "connected/cable unplugged" intermittently. when i opened the radio for further inspection, i discovered that the LEDs were barely illuminating. this to my little knowledge i attributed it to power problem - "just may be" the power being delivered to the radio at the end of the cable is not enough. i tried to convince myself by connecting the end of the cable on to a life device (switch) and the other end on the laptop - believe you me, i was browsing very well.

Please does anyone know what could lead to such a problem? :(

P.S: almost forget to mention that the radio works very well with short cable length.

Re: Power Issue

Posted: Fri Jun 27, 2008 7:20 pm
by msorensen
You should not be dropping more than 2.5 volts (@ 1A) accross a span of 200 feet of cat5.

http://www.demarctech.com/techsupport/poecalculate.htm

it would seem that something is wrong... yea, you knew that ;-)

I would test it using a separate 200' Cat5 cable to see if you get the same result. If a different 200' run works, then I would be replacing RJ45's and otherwise looking for the source of the resistance (power inserter, cable, connectors, etc) to DC current flow in the path between the power supply and the RB133.

obviously, the POE does not use the same pairs as the ethernet connection... so your test of the cable as an ethernet cable does not test the integrity of the DC power path.

My first guess is that at least one of your RJ45's is not making a connection to 1 or more of the 4 wires (2 pairs) being used for POE (Power Over Ethernet) thus decreasing the amount of copper carrying the current, and increasing the DC resistance of the run. Which is also another reason to use Ethernet cable testers that test all 4 pairs from end to end, not just the 2 pair being used for Ethernet....

http://en.wikipedia.org/wiki/Power_over_Ethernet