Return-Path: Received: from mtain-mc08.r1000.mx.aol.com (mtain-mc08.r1000.mx.aol.com [172.29.96.80]) by air-mf03.mail.aol.com (v129.4) with ESMTP id MAILINMF034-8be44c98c40976; Tue, 21 Sep 2010 10:41:13 -0400 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mc08.r1000.mx.aol.com (Internet Inbound) with ESMTP id B5E72380000A6; Tue, 21 Sep 2010 10:41:11 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Oy40D-0008Hi-LE for rs_out_1@blacksheep.org; Tue, 21 Sep 2010 15:39:25 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Oy403-0008HZ-4J for rsgb_lf_group@blacksheep.org; Tue, 21 Sep 2010 15:39:15 +0100 Received: from mail-yw0-f43.google.com ([209.85.213.43]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1Oy402-0004db-0L for rsgb_lf_group@blacksheep.org; Tue, 21 Sep 2010 15:39:16 +0100 Received: by ywj3 with SMTP id 3so1948795ywj.16 for ; Tue, 21 Sep 2010 07:39:07 -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=Jdsv/jzqIiUxapZaxRMvh7dz6uzeb+PPf//kJ7zlSL8=; b=UYlSwZrJR91w+qJC/a+0JU6mgXkG2NcYYfrf5OSIWMhBkh81T3jnwNjRJK++CI4qmL qmNJNSb8HL8MoZ59au/soWOj9stWcHNo4MMVL3IWqOIvQdc94SyfZYzAbMT1tuvaG2IJ NFVr02wRfurh3C37NS3C8iNOm2wB4k1BAv8H4= 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=NJfBTqYmh8m2+nRHfNRktUSp245oxexYXKqaUP/qOs0D9qDUQrh4kQBP2rVM+FptwZ +bx7MPgO/+bqhsnf810juX8TqL1Xh4CRIy870CTEiTd3vHLkxLQLbRDQd7IubP0B+U8o TKBFmiJamWoHnL9cbyO71qWS8+njU5JaBighs= MIME-Version: 1.0 Received: by 10.150.203.4 with SMTP id a4mr4387573ybg.68.1285079947015; Tue, 21 Sep 2010 07:39:07 -0700 (PDT) Received: by 10.231.145.145 with HTTP; Tue, 21 Sep 2010 07:39:06 -0700 (PDT) In-Reply-To: <421083.64004.qm@web86703.mail.ird.yahoo.com> References: <285121.90276.qm@web86704.mail.ird.yahoo.com> <421083.64004.qm@web86703.mail.ird.yahoo.com> Date: Tue, 21 Sep 2010 15:39:06 +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: its back - maybe - Content-Type: multipart/alternative; boundary=000e0cd5d024bff5ba0490c5fd80 X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.8 required=5.0 tests=HTML_30_40,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-d295.1 ; domain : googlemail.com DKIM : pass x-aol-sid: 3039ac1d60504c98c40778d2 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --000e0cd5d024bff5ba0490c5fd80 Content-Type: text/plain; charset=ISO-8859-1 Usually impulsive interference, carriers and the laws of probability. Given a data stream with strong source coding and all original redundancy removed, then any data that passes the error correction tests on receive must then be decoded as something that looks like valid source data. The false decodes you are getting are those bursts of interference that get interpreted as valid-ish tones, and by chance fall into a sequence that the convolutional decoder accepts as a reasonable contribution to the decoding. WSPR codes callsigns assuming a letter or number, followed by a number, followed by three letters or numbers (or spaces). The locator is encoded as a 15 bit value representing any of the 32400 possible locators it could ever be, and power is coded as a 6 bit number showing any of 60 possible power levels. So if the error decoder decides the rubbish/QRN it has received may have enough symbols in the correct position to be a valid WSPR sequence, then whatever pattern of 72 '1's and '0' it lets through to the decoder will always look like a callsign + locator + power level. The error detection circuitry is pretty immune against noise, but impulsive interference and spurious carriers may confuse it You do seem to be getting more than most people though. Andy www.g4jnt.com On 21 September 2010 15:14, Dave Pick wrote: > Andy > > Yes, some very interesting callsigns coming up! Super DX... some of them > appear to be in the middle of the Pacific ocean! > What causes that? > > Dave. > > ------------------------------ > *From:* Andy Talbot > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Tuesday, 21 September, 2010 14:45:07 > *Subject:* Re: LF: its back - maybe - > > Several decodes of the QRP transmission at G3YXM, all at the -25 to -27dB > S/N level, so right on the threshold. > > Dave, you're getting quite a number of false decodes accordng to the WSPR > database. Inpulsive QRM perhaps ? > > Andy > www.g4jnt.com > > > > > > On 21 September 2010 11:47, Dave Pick wrote: > >> Andy >> >> I've put my WSPR back on on 137.5 but as I was setting it up I heard a >> "G8IMR" CW ID so I'll be surprised if I don't get a copy! >> >> Dave >> >> By the way, I had a similar shed conflagration a few years back, it was >> better than yours - the fire brigade attended! >> >> ------------------------------ >> *From:* Andy Talbot >> *To:* rsgb_lf_group@blacksheep.org >> *Sent:* Tuesday, 21 September, 2010 11:10:10 >> *Subject:* LF: its back - maybe - >> >> Hope I'm not typing this too soon, but monitor 137.53kHz (USB dial 136kHz) >> WSPR. >> 600 Watts again >> >> A bucket of water is lying close by this time. >> The coil is now in a brand new plastic dustbin with the variometer control >> brought to the outside world on a plastic spindle. >> >> Nary a bit of aluminium tape in sight >> >> Andy >> www.g4jnt.com >> ps. the WSPR message is still untrue. Its nearer 17dBm ERp than the >> 13dBm is says. >> >> > > --000e0cd5d024bff5ba0490c5fd80 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
Usually impulsive interference, carriers =A0and the laws of probabili= ty.
=A0
Given a data stream with strong source coding and all original redund= ancy removed, then any data that passes the error correction tests on rece= ive must then be decoded as something that looks like valid source data.
=A0
The false decodes you are getting are those bursts of interference th= at get interpreted as valid-ish tones, and by chance fall into a sequence= that the convolutional decoder accepts as a reasonable contribution to th= e decoding.=A0=A0
=A0
WSPR codes callsigns assuming a letter or number,=A0=A0followed by a= number, followed by three letters or numbers (or spaces).=A0The locator= is encoded as a 15 bit value=A0representing any of the 32400 possible loc= ators it could ever be, and power is coded as a 6 bit number showing any= of 60 possible power levels.=A0=A0=A0
=A0
So if the error decoder decides the rubbish/QRN =A0it has received ma= y have enough symbols in the correct position to be a valid WSPR sequence,= then whatever pattern of 72=A0 '1's and '0' it lets throu= gh=A0to the decoder=A0will always look like a callsign + locator + power= level.
=A0
The error detection circuitry is pretty immune against noise, but imp= ulsive interference and spurious carriers may confuse it
=A0
You do seem to be getting more than most people though.=A0
On 21 September 2010 15:14, Dave Pick <davepick@btinterne= t.com> wrote:
Andy

Yes, some very interesting callsigns coming up! Super DX.= .. some of them appear to be in the middle of the Pacific ocean!
What= causes that?

Dave.

From: Andy Talbot <andy.g4jnt@go= oglemail.com>
To: rsgb_l= f_group@blacksheep.org
Sent: Tuesday, 21 Se= ptember, 2010 14:45:07
Subject: Re: LF: its back - maybe -

Several decodes of the QRP transmission at G3YXM, all at the -25 to= -27dB S/N level, so right on the threshold.
=A0
Dave, you're getting quite a number of false decodes accordng to= the WSPR database.=A0 Inpulsive QRM perhaps ?
=A0
Andy
=A0



=A0
On 21 September 2010 11:47, Dave Pick <davepick@btinternet.com> wrote:
Andy

I've put my WSPR back on on 137.5 but as I was settin= g it up I heard a "G8IMR" CW ID so I'll be surprised if I do= n't get a copy!

Dave

By the way, I had a similar shed co= nflagration a few years back, it was better than yours - the fire brigade= attended!

From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
Sent: Tuesday, 21 Septembe= r, 2010 11:10:10
Subject: LF: its back - maybe -

Hope I'm not typing this too soon, but monitor 137.53kHz (USB dia= l 136kHz) WSPR.
600 Watts again
=A0
A=A0bucket of water is lying close by=A0this time.=A0=A0
The coil is now in a brand new plastic dustbin with the variometer co= ntrol brought to the outside world on a plastic spindle.
=A0
Nary a bit of aluminium tape in sight
ps.=A0 the WSPR message is still untrue.=A0 Its nearer 17dBm ERp than= the 13dBm is says.
=A0

<= /div>

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