Return-Path: Received: from mtain-db05.r1000.mx.aol.com (mtain-db05.r1000.mx.aol.com [172.29.64.89]) by air-da07.mail.aol.com (v129.4) with ESMTP id MAILINDA073-863f4cab56142a6; Tue, 05 Oct 2010 12:45:08 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-db05.r1000.mx.aol.com (Internet Inbound) with ESMTP id 95CF9380000B7; Tue, 5 Oct 2010 12:45:06 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1P3AbK-0006aL-LO for rs_out_1@blacksheep.org; Tue, 05 Oct 2010 17:42:50 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1P3AbK-0006aC-4d for rsgb_lf_group@blacksheep.org; Tue, 05 Oct 2010 17:42:50 +0100 Received: from mail-iw0-f171.google.com ([209.85.214.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1P3AbI-0008L1-Dy for rsgb_lf_group@blacksheep.org; Tue, 05 Oct 2010 17:42:50 +0100 Received: by iwn9 with SMTP id 9so132787iwn.16 for ; Tue, 05 Oct 2010 09:42:47 -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=u0ebi2C+zCLdpC6bBbnijqusxlnJ6rxBgdpQvuLM7uw=; b=F7An+3ilCaFs0LkG1B6+t+z581AXB3aDS/6qDEJwh+e7aEj2I0R3tNPpB9E0aWaT/x Lz3/FgVE56CaB3NK9Mo0HptNPx1Sih4laFtTb0WhUvWgj9L6GG5UqfAU0LLXRjU6QMhf qnMuv8P7ml6RDWKadfCsyErXx+f0sOImoKxfA= 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=DHFZXr014ZQTibQWm7LJqUWFB4yooYnZ62eR8tqSV7EgJYoj7uPbSjvMK8/tkPRXT+ sB+NqQjqdcz5QcFugwbN+bBg1ucqoxmi7Cpn4IytyCx+wsmHO54OKy5k/MjS/ijze47y ebh5oVIF+H07p4d/rcBt4stAfvWCjsmIMq+ls= MIME-Version: 1.0 Received: by 10.231.168.21 with SMTP id s21mr12360249iby.123.1286296965551; Tue, 05 Oct 2010 09:42:45 -0700 (PDT) Received: by 10.231.48.8 with HTTP; Tue, 5 Oct 2010 09:42:45 -0700 (PDT) In-Reply-To: References: Date: Tue, 5 Oct 2010 17:42:45 +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: WSPR Dx Content-Type: multipart/alternative; boundary=001636c92e9cb517ed0491e15999 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-d227.1 ; domain : googlemail.com DKIM : pass x-aol-sid: 3039ac1d40594cab56123910 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --001636c92e9cb517ed0491e15999 Content-Type: text/plain; charset=ISO-8859-1 Not quite as low a coincidence as you'd think. IF, and this is the main thing, a chunk on interference has to get past the convolutional / Viterbi data decoder. If your 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 site 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. Up to 650 Watts now the rain has evaporated from the house roof and the ground is a bit drier. And not a wisp of smoke or a flame in sight Andy www.g4jnt.com On 5 October 2010 00:08, James Moritz wrote: > Dear Andy, LF Group, > > Well, this is what 137.5k +/- 100Hz has looked like for the past 22 hours > or so - quite a bit of impulsive and other noise here! > > I am seeing quite a lot of the peculiar "double false decodes", i.e. the > same ficticious callsign decoded twice during a single transmission period, > at different frequencies and with different delta-T. This has happened about > 50 times during the period shown on the screen shot, and makes up a large > majority of the total number of false decodes. I imagine the probability of > this happening actually as a result of random coincidence must be fabulously > tiny - so perhaps some artefact of the decoding algorithm, or a software > bug? > > Cheers, Jim Moritz > 73 de M0BMU > > ----- Original Message ----- From: "Andy Talbot" < > andy.g4jnt@googlemail.com> > To: > Sent: Monday, October 04, 2010 11:09 PM > Subject: LF: WSPR Dx > > > Jim - >> >> You're decoding some wonderful DX on WSPR, including an M6 station at >> 19Mm. >> Impulsive interference or carriers? >> >> Andy >> www.g4jnt.com >> >> --001636c92e9cb517ed0491e15999 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Not quite as low a coincidence as you'd think.=A0=A0 IF, and this= is the main thing, a chunk on interference has to get past the convolutio= nal / Viterbi =A0data decoder.=A0 If your interference has sidebands, then= there is a probability all its sidebands will wobble together.=A0=A0 If= this wobble is interpreted as valid FSK that passes the decoder test, the= n all will result in the same site of bits being decoded.
=A0
Now, the source encoding and removal of all input redundancy means th= an just about any random set of 72 bits that get generated will end up wit= h a valid looking callsign, locator and a power level.=A0=A0 And of course= , all sidebands will give the same result if they've wobbled together.=
=A0
There are probably far more decodes of the interference that get reje= cted, its just those that the laws of probability say must happen occasion= ally, with their=A0sidebands, that generate the multiple hits.
=A0
Up to 650 Watts now the rain has evaporated from the house roof and= the ground is a bit drier.=A0=A0=A0 And not a wisp of smoke or a flame in= sight
=A0
On 5 October 2010 00:08, James Moritz <james.moritz@= btopenworld.com> wrote:
Dear Andy, LF Group,

We= ll, this is what 137.5k +/- 100Hz has looked like for the past 22 hours or= so - quite a bit of impulsive and other noise here!

I am seeing quite a lot of the peculiar "double false decodes&quo= t;, i.e. the same ficticious callsign decoded twice during a single transm= ission period, at different frequencies and with different delta-T. This= has happened about 50 times during the period shown on the screen shot,= and makes up a large majority of the total number of false decodes. I ima= gine the probability of this happening actually as a result of random coin= cidence must be fabulously tiny - so perhaps some artefact of the decoding= algorithm, or a software bug?

Cheers, Jim Moritz
73 de M0BMU

----- Original Message -----= From: "Andy Talbot" <andy.g4jnt@googlemail.com>
To: <rsgb_lf_group= @blacksheep.org>
Sent: Monday, October 04, 2010 11:09 PM
Subject: LF: WSPR Dx

Jim -

You're decodi= ng some wonderful DX on WSPR, including an M6 station at 19Mm.
Impulsiv= e interference or carriers?

Andy
www.g4jnt.= com


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