it is possible to feed a sectoral antenna mANTBox 15s using the PoE source there is a distance of 90m? It works well and there is no guarantee?

Yes, it is possible.

Last week a customer ran a 112m(!) cheap Cat5e cable and powered a SXT Lite5 and it runs like a champ yep.. even runs at 100Mbps FDx

Not advising it, just letting you know it CAN be done.

Menno

The PoE standards where designed to run the full length of an ethernet span, which is 305 ft/100m, on a Cat5 cable.
This is also the maximum allowed length for an ethernet data connection according to ethernet specifications and is a direct consequence of the physical "length" of a minimal ethernet packet on the cable, which has to reach the other end of the cable before transmission ends to allow CDMA collision detection (actually not that important when using switches and UTP, but still enforced by TIA/EIA standards).
Anything longer is sheer luck and off standards, anything less not working is non-compliance.