[Lowfer] 8820 Hz question - maybe OT

[JD]

>>> what are the conditions or parameters for a signal like 8820 Hz to 
>>> change from being contained in the magnetism of a transformer or speaker 
>>> voice coil to being radiated from an antenna?

You are correct that there is no magic frequency for EM radiation to occur, 
as illlustrated by the example Doug gave.

The one absolute condition for radiating an electromagnetic wave at radio 
frequencies is being able to accelerate charge carriers.  We do this by 
pushing RF current through a conductor (the antenna), causing electrons to 
accelerate first in one direction, then the other, repeatedly, for the 
duration of the transmission.  That's pretty much it.

Of course, that's also the challenge...getting enough of that current to 
flow, and not letting the current be balanced by another current 
accelerating electrons in the opposite direction within the same plane.  The 
lower the frequency, the harder it is as a practical matter to get current 
to flow at all in a short Marconi antenna because of all the reactance that 
must be cancelled; or to achieve sufficient separation of the sides of a 
loop antenna to prevent most of the signal from cancelling itself.

John