Go to http://www.maplin.co.uk and search for their stock code L19AG
A useful aerial with 13db forward gain
Or try **broken link removed** - at bottom of page is a yagi, lower gain than the above.
A good yagi at the reciever should do the distance you want, if you also fit one to the transmitter the power will exceed legal limits but you could cover 10 miles :shock: I am told.