[Lowfer] 8820 Hz question - maybe OT

[William E. Isakson]

not only subs Mike, you can use those polar low freq signals to follow the
wave guide made by the earth's magnetic field to the other pole and not
heard in between.
Bill

--------


Bill Isakson     AC6QV
Roseburg, Oregon USA
bill.isakson at gmail.com



On Tue, Dec 2, 2014 at 7:35 PM, N8OOU <n8oou at meekfarm.us> wrote:

> 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.
>>>
>>
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