I am trying to construct a radio and, at the first stage, I have finally detected circuit a signal. My previous attempts have failed and I have discovered that it is because it was not properly grounded.
Originally I was using the ground from my oscilloscope, but it wasn't until I accidentally touched the grounding wire to a my aluminum window frame that all the noise disappeared and a much cleaner, oscillating wave, appeared.
So I would like to know, how do compact AM Radio sets establish a ground? I tried grounding to the wall, grounding to the Earth, and even a medium sized sheet of copper and nothing worked except when I attached it to my aluminium window (which is quite large).
For a while, I wasn't sure if my window was actually acting as an antenna, but, after switching things around (the antenna and the ground), the circuit did not work.
Therefore, I would like to know how compact radios establish a ground? I mean, they don't have a water pipe to connect to so how do they do it? Please do not make references to heterodyning since I am building a simpler version of an AM Radio.
EDIT: Note, I have also tried connecting my ground to the wall ground and it only slightly better than grounding to Earth.