Return-Path: Received: from mtain-db10.r1000.mx.aol.com (mtain-db10.r1000.mx.aol.com [172.29.64.94]) by air-di06.mail.aol.com (v129.4) with ESMTP id MAILINDI061-eaca4cb9ac0f1eb; Sat, 16 Oct 2010 09:43:43 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-db10.r1000.mx.aol.com (Internet Inbound) with ESMTP id 67F4938000081; Sat, 16 Oct 2010 09:43:42 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1P771b-0003Wt-J9 for rs_out_1@blacksheep.org; Sat, 16 Oct 2010 14:42:15 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1P771b-0003Wk-2X for rsgb_lf_group@blacksheep.org; Sat, 16 Oct 2010 14:42:15 +0100 Received: from mail-iw0-f171.google.com ([209.85.214.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1P771Y-0007cb-C5 for rsgb_lf_group@blacksheep.org; Sat, 16 Oct 2010 14:42:15 +0100 Received: by iwn38 with SMTP id 38so2546351iwn.16 for ; Sat, 16 Oct 2010 06:42:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=gamma; h=domainkey-signature:mime-version:received:received:in-reply-to :references:date:message-id:subject:from:to:content-type; bh=vIvlXerw9JXvJuWxIp9wkU7kau6BYTooo2JA+pdQ76M=; b=OeavjEO2xe+ipy1ulP4KcDyrqeS3Fg4ydfWSfqTkaMfHd3Db+tuHZkWP1vaFedIA1z 0e5/jGl8vfv61rEUBCWxzvzzg6x7MUeJUbX+Ll24aNXM+Jzw+dmMcMmLn6bU+JniYg6Z hsNZzaKgsvrkhkR5FbGyubGvbEDMRQBybtPdk= DomainKey-Signature: a=rsa-sha1; c=nofws; d=googlemail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=py0EgftR+jUQxylB0zPvUVv8uUnq677/TEZf0SDXDHaXy45xpw/3KaYXlvEL0/Eh0e drsBliNMP8EYz+TYeJfcxzj6oBdrnfdbA4ID382Lckz4HZlfc6ayoDEBWv8Z+LCCiO2c QlFafF42cJ0mZyvtFyEiJqOP2f2KhGE1gNoX8= MIME-Version: 1.0 Received: by 10.231.174.5 with SMTP id r5mr1683780ibz.132.1287236529327; Sat, 16 Oct 2010 06:42:09 -0700 (PDT) Received: by 10.231.48.8 with HTTP; Sat, 16 Oct 2010 06:42:09 -0700 (PDT) In-Reply-To: References: <20101016141630.434cfad0@svr3.twatt.home> Date: Sat, 16 Oct 2010 14:42:09 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org DomainKey-Status: good (testing) X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: RE: Wierd WSPR spots Content-Type: multipart/alternative; boundary=0016364ecf08128e5d0492bc1c48 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE 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-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-m234.2 ; domain : googlemail.com DKIM : pass x-aol-sid: 3039ac1d405e4cb9ac0e6abf X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --0016364ecf08128e5d0492bc1c48 Content-Type: text/plain; charset=ISO-8859-1 You may be referring to this, I posted a few weeks ago. IF, and this is a big IF, a chunk of interference has managed to get past the convolutional / Viterbi data decoder in the WSPR decoding routine and if this interference has sidebands, then there is a probability all its sidebands will wobble together. If this wobble is interpreted as valid FSK that passes the decoder test, then all will result in the same set of bits being decoded. Now, the source encoding and removal of all input redundancy means than just about any random set of 72 bits that get generated will end up with a valid looking callsign, locator and a power level. And of course, all sidebands will give the same result if they've wobbled together. There are probably far more decodes of the interference that get rejected, its just those that the laws of probability say must happen occasionally, with their sidebands, that generate the multiple hits. So there's some broadband unstable interference with sidebands that manages to occasionally get through and each sideband, as it wobbles in frequency with the others, decodes to a similar result. Andy www.g4jnt.com On 16 October 2010 14:29, Rik Strobbe wrote: > John, > > the "fake twins" occur regulary. > Jim (or someone else) has offered an explanation some time ago, But I'm > afraid I deleted that mail. > > 73, Rik ON7YD - OR7T > > ________________________________________ > Van: owner-rsgb_lf_group@blacksheep.org [ > owner-rsgb_lf_group@blacksheep.org] namens gm4slv [ > gm4slv@sighthound.demon.co.uk] > Verzonden: zaterdag 16 oktober 2010 15:16 > Aan: rsgb_lf_group@blacksheep.org > Onderwerp: LF: Wierd WSPR spots > > Jim, LF, > > > I just noticed 2 spots, in the same minute, from Jim on 136kHz > > 2010-10-16 12:24 HV6KDM 0.137463 -22 3 GB36 0.001 M0BMU IO91vr 14488 > 2010-10-16 12:24 HV6KDM 0.137553 -19 3 GB36 0.001 M0BMU IO91vr 14488 > > The same mis-decoded Callsign & Locator - 2 different frequencies & > different S/N ratios. > > How's that done then? > > John > GM4SLV > --0016364ecf08128e5d0492bc1c48 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
You may be referring to this, I posted a few weeks ago.
=A0
IF, and this is a big IF, a chunk of interference has managed to get= past the convolutional / Viterbi=A0 data decoder in the WSPR decoding rou= tine and if this interference has sidebands, then there is a probability= all its sidebands will wobble together.=A0=A0 If this wobble is interpret= ed as valid FSK that passes the decoder test, then all will result in the= same set of bits being decoded.
=A0
Now, the source encoding and removal of all input redundancy means= than just about any random set of 72 bits that get generated will end up= with a valid looking callsign, locator and a power level.=A0=A0 And of co= urse, all sidebands will give the same result if they've wobbled toget= her.
=A0
There are probably far more decodes of the interference that get re= jected, its just those that the laws of probability say must happen occasi= onally, with their sidebands, that generate the multiple hits.
=A0
So there's some broadband unstable interference with sidebands th= at manages to occasionally get through
and each sideband, as it wobbles in frequency with the others, decode= s to a similar result.
On 16 October 2010 14:29, Rik Strobbe <Rik.Strobbe@fy= s.kuleuven.be> wrote:
John,

the "fake tw= ins" occur regulary.
Jim (or someone else) has offered an explanat= ion some time ago, But I'm afraid I deleted that mail.

73, Rik =A0ON7YD - OR7T

_______________________________________= _
Van: owner-rsgb= _lf_group@blacksheep.org [owner-rsgb_lf_group@blacksheep.org] namens gm4slv [gm4slv@sighthound.demon.co.uk]
Verzonden: zaterdag 16 oktober 2010 15:16
Aan: rsgb_lf_group@blacksheep.org
Onderwerp: LF:= Wierd WSPR spots

Jim, LF,


I just noticed 2 spots, in th= e same minute, from Jim on 136kHz

2010-10-16 12:24 HV6KDM 0.137463 -22 3 GB36 0.001 M0BMU IO91vr 144882010-10-16 12:24 HV6KDM 0.137553 -19 3 GB36 0.001 M0BMU IO91vr 14488
=
The same mis-decoded Callsign & Locator - 2 different frequencies= &
different S/N ratios.

How's that done then?

John
GM4S= LV

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