[Lowfer] 8820 Hz question - maybe OT

[N8OOU]

Clint, Doug, Thanks for the input and concepts. My mind is still twisted 
up on the concept.

Doug, I do remember reading about the ELF stations up north, I don't 
remember that there was a lot of details on how it worked other than 
really long antennas, and real high power. I have been comfortable all 
this time thinking the subs picked up the signals by induced magnetism.


73   de   N8OOU - Mike Meek

On 12/02/2014 03:59 PM, Clint Turner wrote:
> There is no frequency above which an AC electromagnetic signal "starts"
> to radiate - it is all RF to some extent - it just depends on the scale
> of the conductor involved.  Were we (humans) the size of ants, 80 meters
> would be to us the sort of scale that LF/VLF is to us, now, and on a
> planetary scale, LF/VLF wavelengths aren't incredibly long.
>
> In order for a signal of a given frequency to be radiated from antenna
> that is a tiny fraction of its wavelength - which would be the case for
> "audio" frequency RF - there needs to be an efficient means to match
> it.  Practically speaking, this would involve either a wire (very high
> voltage) or a loop (very high current) - either (practically!) being a
> fraction of the wavelength in size.  Neither would have the necessary
> "aperture" to radiate effectively, and as a practical matter either one
> will have tremendous losses:  With the wire antenna it would
> matching/ground losses, with the coil it would be matching and
> resistive/skin-effect/matching dominantly.
>
> Necessarily such a tiny antenna will have a "radiation resistance" of a
> very tiny fraction of an ohm, so if the antenna and/or its
> matching/ground losses were anywhere near an ohm (several ohms is much
> more likely!) you can see that the losses will pile up as orders of
> magnitude!
>
> Fortunately, Shannon's theories dictate that given a low enough signal
> rate with a narrow enough detection bandwidth, even such a ridiculously
> small signal radiated by an installation such as the one assembled may
> be detectable over long distances by people who are willing to go to
> equally ridiculous lengths and spend absurd amounts of time in doing
> so!  (Like me!)
>
> 73,
>
> Clint
> KA7OEI
>
>
> N8OOU wrote:
>> Guys, I have been trying to remember my electronics and physics
>> theory, and can't bring an answer to this question back to the top.  I
>> don't know if it is off topic for the list, if so I apologize, and
>> welcome direct replies.
>>
>> My question is; 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?
>>
>> I'm thinking I remember it being said that at some magic frequency
>> above the audio range a signal starts to radiate.  Obviously that
>> conclusion is not true. I spent some time on google last night and
>> didn't find an answer.
>
> ______________________________________________________________
> Lowfer mailing list
> Home: http://mailman.qth.net/mailman/listinfo/lowfer
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Lowfer at mailman.qth.net
> Post must be less than 50KB total for message plus attachment!
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>