I would recommend to use the standard 2x2 MIMO antennas of EAP110-Outdoor. They perfectly fit to the WiFi chip of the device and cover a large area. No hassle with attenuation due to cables, connectors etc. Just mount the EAP-Outdoor somewhere on the mast or even a wall at least 2.40 meters / 7.8 feet high over ground.
You should
not use a 15dBi external antenna, b/c if cable loss is <= 5dBi you will achieve an antenna gain of 10dBi, which is 10 times the maximum allowed radiation and this could be troublesome. If cable loss is near to 10dBi, the 15dBi antenna will not perform any better, but you lose MIMO (would need two antennas mounted in correct distance to each other). If cable loss is > 10dBi, the antenna will even give worser results than the standard ones. Thus, with a 15dBi external antenna you will always have disadvantages no matter how it actually performs.
However, you could use the 15dBi antenna as a mounting pole for the EAP.
