POE Standards

Hi there, I am a little confused on the powering of a PMP 450i 900MHz SM through an E500.

The KB article below says it's not supported.


However, the 450 Platform User Guide on Page 2-14 says the 900 MHz SM is based off the 450 platform.  The 450i SM and the 450 AP and SM are supported in the KB article above.

What is the difference with the 900 MHz SM that it cannot be powered off the E500?  If someone could provide some insight?



The main issue with the PMP 450i 900MHz SM is that it requires more dc power than the e500 is designed to support (which is in the 12-13W range for the 30V PoE output mode and 12.95W for the 48V PoE output ("802.3af") mode. With an 802.3at PSE powering the e500 we only have about 27W max if you account for 100m of CAT5e cable loss and the same goes for using the Cambium PoE injector (30W). The e500 worst-case dc power draw (max temp, both radios fully loaded and max TX power) is about 12.8W (jsut below the 12.95W 802.3af threshold) and when the PoE output is enabled there is some loss (more with the 30V PoE out since 48V is stepped down to 30V than straight "pass-thru" of the 48V from the Ethernet port power) which leaves only about 12W for the 30V PoE out mode and 13W for the 48V PoE out mode. The PMP 450i 900MHz SM draws up to 15W max (12-13W typical) so it's over the 12W max threshold for the e500 30V output (there is some current limiting done in the e500 for this mode). 

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Thank you very much for the detailed information. This clarifies things for us!