Few things in concern with EVDO signal assuming the tower is working normal.

--> Some people ( as I read in International forums) have complained of loss in ability of in-built antenna

after using an external one.

:: That's NOT a permanent phenomena. Just leave the modem connected to PC without connecting to net for

some hours; the natural capacity of internal antenna is back.

( It happened to my modem. So, just an experience; I am not an expert )

In general, if weird thing happens to modem give it a rest for few hours, then connect to PC ( not internet) and leave it for few hours. Then connect to internet and check out if it's permanently crapped up or was a temporary thing. Needs patience : )

---> The signal reception almost does not depend on the weather conditions like rain, storm etc. But, signal incoming is good in

winters ( because of increase in air density ) and vice versa for summers. Same can be observed in case

of day and night.