Have you ever wondered about....

I sometimes see what appears to me wild NOTAMs for GPS unreliability reports. They never appear to be the same. The latest one I ran across is below

!GPS 05/063 ZOA NAV GPS IS UNRELIABLE AND MAY BE UNAVAILABLE WITHINA 390 NM RADIUS OF 371900N/1154249W OR THE BEATTY VOR /BTY/ 57 DEGREERADIAL AT 58.7 NM, AT FL400 DECREASING IN AREA WITH DECREASE IN ALTITUDE TO 325NM RADIUS AT FL250, 315NM RADIUS AT 10000 FT MSL, AND 240NM RADIUS AT 4000 FT AGL. THIS IMPACT AREA ALSO EXTENDS INTO THE MEXICAN FIR WEF 1006011900-1006012300

First, I am trying to understand where the heck is BEATTY VOR? Second, why is this radius so large? Third, what is causing this?

It says nav gps is unreliable or unavailable from anywhere from 390 NM to 240 NM (at 4000 ft AGL) depending on altitude. That seems to me to be a pretty broad area. The window of time is 4 hours. We are roughly about 260 NM from BTY so the radius does seem to extend into our local area.

It seems there are some references to testing or jamming that is being conducted. This link seems to have a list of scheduled testing:
http://www.navcen.uscg.gov/gps/gpsnotices/GPS_Interference.pdf

and this link seems to talk about the type of activity that is conducted.
http://www.navcen.uscg.gov/gps/gpsnotices/

Anyone else have insight into these occurrences and any firsthand experience with the effects of the unreliable/unavailable GPS?