[Lowfer] 8820 Hz question - maybe OT

[N8OOU]

JD, Bill, and others;

Thank you for contributing more explanation to help my physics 
knowledge.  Even though I am an old guy who should know and understand 
this stuff, some of the old things I thought I understood, have been 
incorrect. It's not easy replacing my 50 yr concept that audio 
frequencies live in a magnetic world contained by metal, ultrasonic is a 
gray in-between world, and anything above is electro and radiates.

Yes, I do now understand from your replys, that resonance of the antenna 
wire is the answer to my question. I just need some time to adjust my 
old concepts.

Thanks

73   de   N8OOU - Mike Meek

On 12/02/2014 11:51 PM, JD wrote:
>>>> 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