Correct. An EMP weapon has never been used, the best we have is educated speculation.
From http://www.unitedstatesaction.com/emp-terror.htm
“The existence of the electromagnetic pulse has been known since the 1940's when nuclear weapons were being developed and tested. However, because of lack of data, the effects of an EMP were not fully known until 1962. At this time, the United States was conducting a series of high-altitude atmospheric tests, code named "Fishbowl." The nuclear explosion, "Starfish Prime," which was detonated in the Pacific Ocean 800 miles from Hawaii, caused an EMP that disrupted radio stations and electrical equipment throughout Hawaii. Consequently, in 1963, the United States and the Soviet Union signed the Atmospheric Test Ban Treaty to counter the considerable threat posed by EMPs. Unfortunately, the destructive potential of an EMP increases everyday as society becomes evermore technological because of an escalating dependence on electronics. “
Now if we just knew what 'disrupted' meant...
I suggest that electronics systems in 1962 were far different than today’s. Extrapolating 46-years old data based on ancient systems is not sound scientifically. While I’m sure there are theoretical reasons to worry about EMP, I would be cautious in accepting them based on data at hand.
Interesting because back then electronics were cruder thus more hardened just by the way they were made