You're experiancing "drop offs" because you are running netstumbler when connected to your home network. Why are you doing this anyway? Read the readme file, it states how netstumbler should be used.
As for sitting right next to your access point, don't do that either; you'll ruin the radios in the access point and your card by being too close.
-edit- King_ice_flash beat me to it
I hope it feels good
