Here is something that might be helpful.  The company claims 16 dBi gain
and 120 degree spread.  Not omni, but might work depending upon your
actual topography.  It's cheap, so....   I believe it's also 5GHz
(802.11ac) only which may or may not be okay with you.  Less interference
on that band, much less.   Maybe 3 on a pole to get 360 degree coverage.
They have a lot of other interesting equipment as well, ie microwave PTP
links and Ethernet bridges.  I've never used any of it, but the reviews
seemed decent.  I'm thinking of buying something like this now.  ;)  I
need to communicate with some ESP8266 based sensors that are kinda far
away and down low.

https://www.amazon.com/Ubiquiti-LiteBeam-802-11ac-built-Degree/dp/B019M0KK
44/ref=3Dsr_1_fkmr0_1?s=3Delectronics&ie=3DUTF8&qid=3D1507755240&sr=3D1-1-f=
kmr0&keyw
ords=3Dubiquiti+litebeam+ac+ap

Here is the manufacturer's page:
https://www.ubnt.com/airmax/litebeam-ac-ap/
--=20
http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.