What hops around? The speed? MPG?
Set your PPM to 8200 then follow the calibration procedure here...
Mpguino calibration - EcoModder
If you scroll over to a screen that shows speed check to see if the speed is erratic. If it is you could have interference or may need a switch debounce circuit. Look here...
http://ecomodder.com/forum/showthrea...ino-25144.html