Is it possible to create a long range 2.4ghz wireless network without using directional antennas because this is for an access point. I have placed a router and antenna 18m from ground but I am getting around 80 meters. There is not much interference from other routers on ch 13 in my area (Athens). I don't need any high speeds or fancy functions, just the minimum required for a half-rate voip call, so 2 or 1 mbps is fine. I can't place access points in the coverage area because its public areas where its not secure. Also, the client devices are smartphones and laptops, which means I can't add better antennas to them.

Any suggestions on what to buy (Access Points, amplifiers, antennas, filters, duplexers?)
Which is better for just pure distance, B G or N?
Should I use encryption or not for more range (network security not important since the network wont have internet access, will be just for voip and the voip server is secure)

80 meters seems pretty short range. what access point are you using? Is there a power adjust control in the software? The other problem is that with a bi-directional link, the smartphones and laptop performance may be causing the problems. Better Antennas would be the first step. Directional antennas would be best, but there are likely better "omni" antenna's than the little rubber stubs you get with most AP's

Using this AP http://www.tp-link.com/en/download/TL-WR941ND_V5.html, I already have the best omni antennas you can buy for that router.