You're probably right! I did actually try to rip the heating element
out of a 2kW electric fire to use as just such a test load, but the
manufacturers had used some really devious sort of screw heads to keep
the two casings together. :-(
Failing some serious resistance wire, the only other 'to hand' option
is to hook up the HF mobile and key-up; but I don't have a sufficiently
gutsy dummy load or antenna to dump 100W into, I'm afraid. :-(