Re: LF: VLF THOUGHT

[Warren Ziegler <wd2xgj@gmail.com>]

Mal,

    You seem to be intent on ignoring the basic physics. 

An 8.97Kcs audio tone is attenuated at 130dB/km. 

You are proposing concentrating the sound in one direction, analogous to a directive antenna, still with say 10kW and an 'antenna' (actually speaker directivity)  gain of say 30dB you would start out with effectively 10MW, but with 130dB/km you would be down to 1 microwatt at a distance of 1km !!! 

Ten MEGAWATTS becomes 1 MICROWATT after 1km at 8.97 kHz!!!

Case closed!

On Wed, Sep 1, 2010 at 12:13 PM, mal hamilton <g3kevmal@talktalk.net> wrote:

With all the energy concentrated into a single tone on 8.97 Kcs  it could well travel a considerable distance with a few Kilowatts of audio beamed in an arranged direction, especially along a valley.

I am surprised that the high voltage 50 Hz electricity overhead distribution network is not heard over great distances by ear.

 

g3kev

 

----- Original Message -----

From: Warren Ziegler

To: rsgb_lf_group@blacksheep.org

Sent: Wednesday, September 01, 2010 3:31 PM

Subject: Re: LF: VLF THOUGHT

Rik,

   Krakatoa exploded with the equivalent force of 200 Megatons of TNT, bigger than the largest Hydrogen bomb and 13,000 times the size of the nuclear explosion that destroyed Hiroshima.

 

   That said, I believe that what was hear at a distance was still the low frequency rumble, 100Hz is attenuated at only 0.3dB/km while 10kHz is attenuated over 150dB/km.

Best to stick with EM waves as opposed to sound.

- 
73 Warren K2ORS
                WD2XGJ 
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1

On Wed, Sep 1, 2010 at 3:58 AM, Rik Strobbe <Rik.Strobbe@fys.kuleuven.be> wrote:

All,

here some real "DX":The explosion of the Krakatoa (1883) was heard in Perth  (Australia), 3100 km away, and on the island of Rodrigues, 5000 km away.

73, Rik  ON7YD
________________________________________
Van: owner-rsgb_lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens Klaus von der Heide [v.d.heide@on-line.de]
Verzonden: woensdag 1 september 2010 9:43
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: Re: LF: VLF THOUGHT

Hello All,


two years ago someone disturbed my breakfast by a deeply
hammering disco sound. So I took my car to search for
the source. Surprisingly, the sound decreased to nearly
zero when I drove some kilometers in that direction where
the sound seem to come from. The Odyssey took 45 minutes.
But finally I found the open-air disco 20 km from my home
in a lonely wood.

Indeed, the sound took nearly 60 seconds from there to my
home. That's more than a thunder usually reaches.

More than thousand square-kilometers where contaminated,
including 23 protected nature resevats.

Yes we can, but Mankind should not do everything what it can.


73!

Klaus, DJ5HG

-
 

--
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1