I have an old Belkin G router that works well but i am trying to get more wireless range so decided to upgrade to an N router. I have now had 3 N routers that have all failed to connect to a line. (2 belkins, 1 linksys). While these new routers are unable to find a line the old one has no problem. I know the line quality is poor as we are at the end of the line, miles from the exchange. Does anyone know if the N routers need a better line than the old G routers or have any other theories as to why i have this problem?

The routers have nothing to do with how far you are from the exchange, only how far you are from your "gateway" the Cable/DSL Modem. The router sits between your computer, and your modem, and simply connects two networks - your network (everything on your side of the router) and the Internet.

Also note that routers are not wired or wireless. They are network devices that connect (often in the same box) to Ethernet 10/100 4-port switches, and optionally, to a WAP, a wireless access point.

This sounds like your computer were not reset, and setup for the new routers, or WAPs. Were you able to log into the router's menu?

I can access the routers menu and set up pages etc but the problem is they are unable to pick up the adsl line. the l.e.d indicators flash to show they are trying to get the line but are unable to do so. (all except my trusty old G router).

I doubt 3 routers are bad, instead it sounds like you did not reset your modem. I would power down your whole network (modem, router, and computers) for about 2 minutes. Then power on the modem and wait until lights stabilize, then power up the new router and configure as per your ISPs instructions for setting up a computer, and wait for lights, then power, one at a time, the computers.

You might want to look in the G router to see if it has any ISP unique settings you need to enter into the N router.