Return-Path: Received: from mtain-ma04.r1000.mx.aol.com (mtain-ma04.r1000.mx.aol.com [172.29.96.12]) by air-df01.mail.aol.com (v129.4) with ESMTP id MAILINDF011-5ee24c7d59d1b8; Tue, 31 Aug 2010 15:36:49 -0400 Received: from post.thorcom.com (post.thorcom.com [193.82.116.20]) by mtain-ma04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 8266D38000BF7; Tue, 31 Aug 2010 15:34:42 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1OqWag-0006UM-Pi for rs_out_1@blacksheep.org; Tue, 31 Aug 2010 20:33:54 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1OqWag-0006UB-6H for rsgb_lf_group@blacksheep.org; Tue, 31 Aug 2010 20:33:54 +0100 Received: from smtp7.freeserve.com ([80.12.242.2] helo=smtp6.freeserve.com) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1OqWae-0002cY-1g for rsgb_lf_group@blacksheep.org; Tue, 31 Aug 2010 20:33:54 +0100 Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3j24.me.freeserve.com (SMTP Server) with ESMTP id 87B9B30000AA for ; Tue, 31 Aug 2010 21:33:44 +0200 (CEST) Received: from me-wanadoo.net (localhost [127.0.0.1]) by mwinf3j24.me.freeserve.com (SMTP Server) with ESMTP id 77EFC30000AF for ; Tue, 31 Aug 2010 21:33:44 +0200 (CEST) Received: from AGB (unknown [91.110.90.106]) by mwinf3j24.me.freeserve.com (SMTP Server) with SMTP id 21A0230000AA for ; Tue, 31 Aug 2010 21:33:44 +0200 (CEST) X-ME-UUID: 20100831193344137.21A0230000AA@mwinf3j24.me.freeserve.com Message-ID: From: "Graham" To: References: <000a01cb493d$fb8f3410$0401a8c0@xphd97xgq27nyf> In-Reply-To: Date: Tue, 31 Aug 2010 20:33:43 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8089.726 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8089.726 X-Antivirus: avast! (VPS 100831-0, 31/08/2010), Outbound message X-Antivirus-Status: Clean X-Spam-Score: 2.3 (++) X-Spam-Report: autolearn=disabled,EXTRA_MPART_TYPE=0.815,FUZZY_OCR_WRONG_CTYPE=1.500,HTML_MESSAGE=0.001 Subject: Re: LF: VLF THOUGHT Content-Type: multipart/related; type="multipart/alternative"; boundary="----=_NextPart_000_00C0_01CB494B.CDD5D930" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.9 required=5.0 tests=HTML_30_40,HTML_MESSAGE, MISSING_OUTLOOK_NAME autolearn=no version=2.63 X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false x-aol-global-disposition: G X-AOL-VSS-INFO: 5400.1158/62612 X-AOL-VSS-CODE: clean x-aol-sid: 3039ac1d600c4c7d595142a5 X-AOL-IP: 193.82.116.20 X-AOL-SPF: domain : blacksheep.org SPF : temperror ------=_NextPart_000_00C0_01CB494B.CDD5D930 Content-Type: multipart/alternative; boundary="----=_NextPart_001_00C1_01CB494B.CDD5D930" ------=_NextPart_001_00C1_01CB494B.CDD5D930 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Not in water =20 From: Warren Ziegler=20 Sent: Tuesday, August 31, 2010 8:24 PM To: rsgb_lf_group@blacksheep.org=20 Subject: Re: LF: VLF THOUGHT Mal,=20 An interesting thought but if you keep the signal above the normal= hearing range the attenuation is severe! At 9 kHz the attenuation of sound is 130 dB/km. At 20kHz the attenuat= ion of sound is over 500 dB/km !!!! This is why distant thunder sounds like a low rumble, all the high fre= quency components have been attenuated. See: http://resource.npl.co.uk/acoustics/techguides/absorption/ and=20 http://www.csgnetwork.com/atmossndabsorbcalc.html --=20 73 Warren K2ORS WD2XGJ=20 WD2XSH/23 WE2XEB/2 WE2XGR/1 On Tue, Aug 31, 2010 at 2:54 PM, mal hamilton = wrote: I see 15 Kilowatt audio amplifiers advertised, therefore there must= be a speaker system, public address horns available for such amplifie= rs.=20 If one of these speaker horns was directed line of sight towards the= horizon or a mountain top and a suitable dish positioned at the recei= ve end, it must be possibel to intercept such a signal at audio freque= ncies. eg Transmit a tone which could be keyed at 9 - 20 Kcs and see= what distance could be covered. Keeping the signal just above the normal human audio range would avo= id interference. or just TX a signal at say 5 Kcs and see how far it could be heard= by ear with this sort of power, maybe further than the same signal tr= ansmitted by radio means, except one had an exceptionally large antenn= a Maybe a NOV is required for this experiment!!!! de g3kev =20 =20 ------=_NextPart_001_00C1_01CB494B.CDD5D930 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Not  in water  

Sent: Tuesday, August 31, 2010 8:24 PM
Subject: Re: LF: VLF THOUGHT

Mal,=20
   An interesting thought but if you keep the signal ab= ove the=20 normal hearing range the attenuation is severe!
 At 9 kHz the= =20 attenuation of sound is 130 dB/km. At 20kHz the attenuation of so= und is=20 over 500 dB/km !!!!

This is why distant thunder sounds like a low rumble, all the hig= h=20 frequency components have been attenuated.

See:


-- 
73 Warren K2ORS
        &n= bsp;=20       WD2XGJ 
         = ;  =20     WD2XSH/23
           =  =20   WE2XEB/2
              &n= bsp;=20 WE2XGR/1



On Tue, Aug 31, 2010 at 2:54 PM, mal hamilton= <g3ke= vmal@talktalk.net>=20 wrote:
I see 15 Kilowatt audio amplifiers= advertised,=20 therefore there must be a speaker system, public address horns avail= able for=20 such amplifiers.
If one of these speaker horns was= directed line=20 of sight towards the horizon or a mountain top and a suitable dish= positioned=20 at the receive end, it must be possibel to intercept such a signal= at audio=20 frequencies. eg Transmit a tone which could be keyed at 9 = -=20 20 Kcs and see what distance could be covered.
Keeping the signal just above the= =20 normal human audio range would avoid interference.<= /DIV>
or just TX a signal at say 5 Kcs an= d see how=20 far it could be heard by ear with this sort of power, maybe fur= ther than=20 the same signal transmitted by radio means, except one had an except= ionally=20 large antenna
Maybe a NOV is required for this=20 experiment!!!!
de g3kev
 
 
 
  



 


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