[sudosysgen]

A gamma knife-type thing would require much higher frequencies than are compatible with the theory because otherwise you get diffraction since the wavelengths are so large. It's very unlikely you'd be able to do such a thing with 20-12 cm wavelength radiation, the calculated location would be meters big and it would be detectable everywhere.

[lend000]

Masers have been around longer than Lasers [0].

I don't know how building walls would affect coherent radiation at various frequencies, but if 80% of the energy made it to the destination, the other 20% could explain the variety of symptoms experienced in the room.

[0] https://en.wikipedia.org/wiki/Maser#:~:text=A%20maser%20(%2F....

[sudosysgen]

The only maser that would fit the bill is a hydrogen maser with a frequency of around 1.4Ghz.

That's a wavelength of 21cm.

That means that your beam waist is never going to be less than 21cm, which means that your beam divergence is going to be of at the very minimum 0.21/pi radians = 3.8 degrees, likely twice that.

That's just not targeted enough to be able to hide the massive EM interference it would cause (like, instantly destroying electronics). And also, if the transmitter was 200 meters away, it would have to be dozens of meters big, assuming you got some lending system. Otherwise, it would still be huge, but it would also spew radiation at a truncated cone with a radius in the meters.

Also, building walls would certainly deflect a lot of the radiation and cause decoherence but also heating and destruction of electronics.

In any case, if it was any kind of EM weapon at a suitable frequency, it would be incredibly detectable and we wouldn't have this discussion.