The issue is less likely to be range than line of sight. Most half decent receivers will pick up transmissions from quite long distances if the transmitting station (fixed or mobile) has reasonable power - and most aircraft and aviation fixed stations have - though some will be more powerful than others. However, any obstruction to radio waves such as hills, some buildings, vehicles, etc - even the curvature of the earth - will reduce or eliminate any chance of reasonable reception. Some careful positioning of your receiver and antenna with a bit of trial and error may help and if you are right on the margin of the reception area you may find some days are better than others as even atmospheric conditions can play a part.
