Wireless Access

Can i put Ap-314 in a plastic box outdoor and put its outdoor antenna  "AP-ANT-19" ... Is it a good practice ?

Ap-314 have 4 antenna connectors...How many minimum and Maximum "AP-ANT-19" external antennas can be used with ap-314?

What if i use 1 external antenna for one accesspoint as the antenna gives omni directinal coverage... what is the advantage of using all 4 antennas?

Please see the Buying Guide here:  http://www.arubanetworks.com/assets/og/OG_AP-310Series.pdf

You need two antennas for each band, otherwise you will have performance issues.

It is always better to get an outdoor-rated AP because they are already weatherproofed.  A plastic box might protect it from moisture but you also might need to figure out how to keep it cool in that enclosure.  It is better to get an outdoor-rated AP in the long run.

Actually with the 315, there are four dual-band antenna connectors. So it's more than two per band, you need all four dual-band antennas for the AP (same number, but I wanted to make sure that no one thinks 2 are for 2.4Ghz and 2 are for 5Ghz. 

Colin is ABSOLUTELY correct, you should be using outdoor APs for outdoor environments. There is virtually no Wave2 benefit outdoors (only within 20-30ft max), due to the nature of MU-MIMO, and you will get overall better performance at range with outdoor APs because they have better radios built for outdoor environments. 

By the time you buy an indoor AP, the NEMA box, the bulkhead connectors, the LMR cables to the antennas, the antennas themselves, etc, the labor to install and hang, etc, your 275+mounting bracket will be less expensive AND perform better. 

Also to add, ESPECIALLY with Wave2 APs, you need to deploy with ALL four antennas. Deploying with less than four will result in significant coverage and performance decreases, and will not provide ANY MU-MIMO with 2 or less antennas (with three it's still not great). You need all four antennas for 4x4 MU-MIMO APs.