[morzh]

Someone (I forgot who it was) has already posted a thread with the same effect described in, when a particular load is turned on and the hum disappears.

I then replied that this is the case in my big room - I turn the lobby lights on and the radio that has a strong buzz when tuned in stops buzzing or the buzz (hum) gets reduced by a lot.

Well, I have just confirmed that it is the case pretty much around the whole house: in my 90 on my working table in my office the hum practically stops when I turn on that lobby lighting fixture which BTW has 8 CCFLs in it.

This so far is the only load that has that effect on the reception.
Light in the adjacent rooms or in the office do not have eny effect.

Since I do not know my house wiring in fine details, I could only theorize the load is just in the licky place, like an end of transmission line and it terminates it.....

Beats me.