I would second the recommendation for trying different locations for the tower. At one point I had so many problems with "dead spots" with my exploring rover (that needs to communicate with the map making/route finding software running on the PC), (...) (25 years ago, 6-Dec-99, to lugnet.robotics.cybermaster)
(...) I would suspect that antenna placement, and possibly considering a different antenna design, would make a huge difference. Look in some radio books for things like Yagi designs. Give you much more range, but also make the antenna very (...) (25 years ago, 14-Dec-99, to lugnet.robotics.cybermaster)
