Yes there is. a lot depends on your antenna. I have on my motor home a Directional Yagie 16db, connected to a 500mW unit. Most of the time you are connecting to a home , which if lucky is 100mW and has a 3db antenna. The yagie will amplifly the weak sugnal comming in and work much better, and for transmitting back , you can reach up to 30km , but they can not reach you back,
AMU-2405G-SMA---Zigwire
AMU-2405G-SMA 802.11g/b 500mW , AP/Client/Repeater/Bridge; LED Wan/Lan/Power; Lighting arrestors protection; Stainless Steel adjustable mounting bracket;No internal antenna panel; Plastic outdoor weatherproof case; -30c~65c ,120/240~48vdc power ,up to 30km with 16 db yagie
This will do it for you .