Just re-read the paper
This part interested me - the NG is the group who have not previously reported symptoms regarding mobile phone usage, whereas the SG are people who claim to be symptomatic.
"The NG reported less headache during sham exposure
compared to the SG. The proportion of subjects who reported headache was higher during RF
exposure than during sham exposure in the NG but not the SG group."
So in fact, the "symptomatic" group reported as having more headaches period and couldn't tell the difference between real exposure and fake exposure. The "non-symptomatic" group actually did experience a real increase in headaches with real exposure.
If anything, this proves that the "symptomatic" group actually make themselves feel worse. By assuming that they have the symptom, they conjure up a headache regardless of exposure (or not) to a signal, so eventually the signal itself becomes meaningless in the wake of their own imagination. Really then, that part of the experiment holds no value when performed on "symptomatic" people, as they will develop their own headache just from thinking they may have had exposure to a signal.
Of course, the non-symptomatic crowd did show an increase in headaches with a real signal, which would lend weight to the argument of real effects.
Though my view has not changed that this test group was too small to get any definitive result.