I don't think telepathy can be due to the brain transmitting electromagnetic waves, as that would be measurable.
There is an Italian psychiatrist, Ferdinando Cazzamalli (a wikipedia article about him is:
https://en.wikipedia.org/wiki/Ferdinando_Cazzamalli ), who claimed to have discovered high frequency electromagnetic waves emitted by the brain.
His book, "the Radiating Brain", may be downloaded here:
http://documents.theblackvault.com/documents/parapsychology/TheRadiatingBrain.pdf .
An excerpt from this book (pp. 84-85):
From this synthesis which I have given, which is the experimental result of one year's research, it stands out clearly that electromagnetic phenomena radiate from the human subject under certain psychic conditions, and that these radiations do indeed come from the brain.
This is the first time, as far as I am concerned, outside the collection of rather vague hypotheses and imprecise, indirect deductions, that such a direct statement can be made on experimental grounds.
This research seems to have been made around 1930, and has been criticized.
The emission spectrum of the brain seems to have never been measured seriously (it is known for the sun, but not for the brain; its non-thermal part would be of great interest), although (thermal) microwave radiation from the brain (at a frequency of about 1 GHz) has been measured (very) seriously, see for example:
Progress In Electromagnetics Research, Vol. 117, 83–101, 2011
NON-INVASIVE MICROWAVE RADIOMETRIC SYSTEM
FOR INTRACRANIAL APPLICATIONS: A STUDY
USING THE CONFORMAL L-NOTCH MICROSTRIP
PATCH ANTENNA
N. P. Asimakis, I. S. Karanasiou *
, and N. K. Uzunoglu
Microwave and Fiber Optics Laboratory
School of Electrical and Computer Engineering
National Technical University of Athens
http://ww.jpier.org/PIER/pier117/06.10122208.pdf
or
J. W. Hand et al., “Monitoring of deep brain temperature in infants
using multi-frequency microwave radiometry and thermal modelling,”
Physics in Medicine and Biology, vol. 46, no. 7, p. 1885, 2001.
https://www.researchgate.net/profil..._modelling/links/02e7e5278991936cf7000000.pdf
(both articles are free, but they are complicated).
One might ask why the scientific community has spent so little time and energy investigating electromagnetic radiation from the brain, particularly in the short wave band (not microwave band), which is known for its long distance transmissions with little power. A possible explanation, of a somewhat sinister nature, is that they want to hide or to cover up the existence of a specific worldwide telepathic phenomenon, related to a specific person.