Return-Path: Received: from mtain-mj04.r1000.mx.aol.com (mtain-mj04.r1000.mail.aol.com [172.21.164.88]) by air-ma07.mail.aol.com (v129.4) with ESMTP id MAILINMA074-b52f4d7bf71a98; Sat, 12 Mar 2011 17:43:38 -0500 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mj04.r1000.mx.aol.com (Internet Inbound) with ESMTP id 2DEDF3800008E; Sat, 12 Mar 2011 17:43:36 -0500 (EST) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1PyXWT-0000AI-Lv for rs_out_1@blacksheep.org; Sat, 12 Mar 2011 22:42:57 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1PyXWS-00009z-Vk for rsgb_lf_group@blacksheep.org; Sat, 12 Mar 2011 22:42:56 +0000 Received: from mail-iy0-f171.google.com ([209.85.210.171]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1PyXWQ-00085E-Hm for rsgb_lf_group@blacksheep.org; Sat, 12 Mar 2011 22:42:56 +0000 Received: by iyf40 with SMTP id 40so5068494iyf.16 for ; Sat, 12 Mar 2011 14:42:47 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type; bh=K3o7CTX2hK6afz500dtt3VMordXsNGkzEgLtgBF84E4=; b=rfyyzh0GhdUWVWVvIPh35xQPvyo+0+HjjW2zilSuGgIakCZuFBqK5Z1tR3IMHVpBy8 iwIur+F/Ktzm1gBGql/ps4o0KpyhldeeNR2LThUhwdC4ZtRkbx/Luccm7FcT1oxpPSfH 9L0AJRShzHFu6XA4PlGi8aZ8IQ2OUcYnfMMsg= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; b=DR8/wqPuuR7TSPHwZAl54eKGSf4RgNP3N57/4vOMQrh7CifnuOzeHsLNdQnaTERyI/ YHxuIYjb7jwnt5iD4MHo+lXl4NY/SpnRFOWOF955iqCPjKejWdjCrDDjTch2iHOcKi7J uoNVeiBz2BLeS+8bzOy76Ohn1e5jtm0Hcx7xU= MIME-Version: 1.0 Received: by 10.231.176.223 with SMTP id bf31mr8488123ibb.28.1299969767747; Sat, 12 Mar 2011 14:42:47 -0800 (PST) Received: by 10.231.199.197 with HTTP; Sat, 12 Mar 2011 14:42:47 -0800 (PST) In-Reply-To: <4D7BF0D8.6030704@iup.uni-heidelberg.de> References: <006301cbe00d$762f0220$0401a8c0@xphd97xgq27nyf> <4D7BF0D8.6030704@iup.uni-heidelberg.de> Date: Sat, 12 Mar 2011 22:42:47 +0000 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: VLF traces Content-Type: multipart/alternative; boundary=00504502ecd539b1cc049e50ccfa X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: * X-Spam-Status: No, hits=1.6 required=5.0 tests=CELL_PHONE_BOOST,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-d280.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039400c89a84d7bf7183466 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none X-Mailer: Unknown (No Version) --00504502ecd539b1cc049e50ccfa Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable err... mmmm... perhaps someone else may care to explain some of our special reserved callsigns :-) 'JNT 2011/3/12 Stefan Sch=E4fer > Andy, > > I agree 100% but who is G9BOF? > > 73, Stefan > > Am 11.03.2011 23:28, schrieb Andy Talbot: > > Can I point out that a carier that appears at a known time and on a know= n > frequency IS modulated. It is on off keyed. (Well...off/on anyway :-) > The only way that a carrier can be unmodulated is if it has been there= since > the beginning of (RF)time and is never switched off, ever, never, befor= e > the end of (RF)time. Its appearance or disappearance is information;= what > that info means depends on how it has been coded. > > Any switching, at all, introduces modulation and widens the bandwidth,= and > therefore counts as a means of identification if the meaning of the on/o= ff > is pre-arranged. > > In comms-theory-speak If G9BOF makes the announcement "I'll be > transmitting on Sunday at 1300z on 8910.0004Hz" he has now generated a > codebook. The appearance of the carrier at that point in time indicate= s a > single bit of information, which by reference to the code boook means G9= BOF > is sending a '1'. No carrier detected,he is sending a '0', or there has > been a bit error. In other words, no error correction.or detection has > been performed. If G9BOF now makes another announcement that "I'll swi= tch > it off at 2358z" he has added another entry to the code book. If the > carrier really does go off then, the two bits of information together= make > a dual-redundant pair, the minimum needed for error detection. > > If G9BOF also makes the statement that "my signal is stable and accurate > to 1mHz" and another signal appears in the passband that is 2mHz away,= or > wobbles by 1.5mHz, then is is not G9BOF, and error detection will flag= it as > not valid. If a receiving station cannot detect this error, and > incorrectly assesses the carrier then the Rx has used the wrong codebook= , > and therefore cannot be deemed to be listening to G9BOF at all. > > All a rather extreme and somewhat petty example of coding theory and er= ror > detection, but its exactly the same as simple Hamming codes all the way > thorough to reed Solomon. And... I'm not sure how G9BOF getting his > frequency or time wrong would fit into the coding theory. > > So, conclusion, a carrier as stable and on the exact frequency as stated= , > at the right time is going to be valid. If you have no way of proving= it > really is as stable as quoted, or in the right place, *you've no right= to > question its validity*. > > And anyway, how many spurious signals can even give any pretence to bein= g > stable in these terms - if you think they are, get a better receiver. = We > are talking about 0.1ppm over the duration of a signalling element as a > minimum frequency stability requirement for most serious VLF through LF > signalling - which means a quite good TCXO, an average to middling OCXO > or ideally a locked source. If you can't manage this, do not cry 'foul= ' > when others do. > > Andy > www.g4jnt.com > > > > > > On 11 March 2011 21:30, Markus Vester wrote: > >> Dear Mal, >> >> with all due respect, I very much disagree here. >> >> Whenever I see a clear trace appear at the right time and within a mill= iHz >> of a confirmed and correctly calibrated frequency, I have hardly a doub= t >> about the validity of the reception. Even more so if the transmission= can >> be >> verified by comparison to a calibrated grabber in another location. >> >> It seems that the G3KEV antenna does have excellent sensitivity at VLF.= It >> would be fantastic if you could augment that with a stable, properly >> calibrated, and narrowband reception system. SpecLab has made that so= easy >> now - throw out the wildly drifting "receiver", connect your antenna >> directly to the soundcard instead, lock to one of your MSK neighbours= (GBZ >> or GQD), and your in the game. >> >> Best regards, >> Markus (DF6NM) >> >> >> From: mal hamilton >> Sent: Friday, March 11, 2011 5:57 PM >> To: rsgb >> Subject: LF: VLF traces >> >> >> I can see a couple of vy weak traces around 8970 but this is no guarant= ee >> who it might be because there is no ID. Frequency alone is not a VALID >> report- it could be anything. >> G3KEV >> >> >> >> > --00504502ecd539b1cc049e50ccfa Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable
err...
mmmm...
=A0
perhaps someone else may care to explain some of our special reserved= callsigns :-)
=A0
'JNT


=A0
2011/3/12 Stefan Sch=E4fer &l= t;schaefer@iup.uni-heide= lberg.de>
Andy,

I agree 100% but= who is G9BOF?

73, Stefan

Am 11.03.2011 23:28, schrieb Andy= Talbot:=20
Can I point out that a carier that appears at a known time and on a= known frequency IS modulated.=A0=A0 It is on off keyed.=A0 (Well...off/on= anyway :-)=A0=A0=A0 The only way that a carrier can be unmodulated is if= it has been there since the beginning of=A0 (RF)time and is never switche= d off, ever, never, before the end of (RF)time.=A0=A0 Its appearance or di= sappearance is information;=A0 what that info means depends on how it has= been coded.
=A0
Any switching, at all, introduces modulation and widens=A0the bandwid= th, and therefore counts as a means of identification if the meaning of th= e on/off is pre-arranged.=A0=A0
=A0
In comms-theory-speak=A0 If G9BOF makes the announcement "I'= ll be transmitting on Sunday at 1300z on 8910.0004Hz" he has now gene= rated a codebook.=A0=A0 The appearance of the carrier at that point in tim= e indicates a single bit of information, which by reference to the code bo= ook means G9BOF is sending a '1'.=A0 No carrier detected,he is sen= ding a '0', or there has been a bit error.=A0=A0 In other words,= no error correction.or detection has been performed.=A0=A0 If G9BOF now= makes another announcement that "I'll switch it off at 2358z&quo= t; he has added another entry to the code book.=A0 If the carrier really= does go off then,=A0 the two bits of information =A0together make a dual-= redundant pair, the minimum needed for error detection.=A0=A0
=A0
If G9BOF=A0also makes the statement that "my signal is stable an= d accurate =A0to 1mHz" and another signal appears in the passband tha= t is 2mHz away, or wobbles by 1.5mHz, then is is not G9BOF, and error dete= ction will flag it as not valid.=A0=A0 If a receiving station cannot detec= t this=A0error, and incorrectly assesses the carrier then the Rx has used= the wrong codebook, and therefore cannot be deemed to be listening to G9B= OF at all.=A0=A0
=A0
All a rather extreme and somewhat petty =A0example of coding theory= and error detection,=A0=A0but its exactly the same as simple Hamming code= s all the way thorough to reed Solomon.=A0 And... =A0I'm=A0not sure ho= w G9BOF getting his frequency or time wrong would fit into the coding theo= ry.
=A0
So, conclusion, a carrier as stable and on the exact frequency=A0as= stated, at the right time is going to be valid.=A0=A0 If you have no way= of proving it really is as stable as quoted, or in the right place, <= strong>you've no right to question its validity.
=A0
And anyway, how many spurious signals can even give any pretence to= being stable in these terms - if you think they are, get a better receive= r.=A0=A0 We are talking about 0.1ppm over the duration of a signalling ele= ment as a minimum frequency stability requirement for most serious VLF thr= ough LF signalling - which=A0means a=A0quite good TCXO, an average to midd= ling=A0OCXO or=A0ideally a locked source.=A0=A0 If you can't manage th= is, do not cry 'foul' when others do.
=A0
Andy
=A0
=A0
=A0

=A0
On 11 March 2011 21:30, Markus Vester <mar= kusvester@aol.com> wrote:
Dear Mal,

= with all due respect, I very much disagree here.

Whenever I see a= clear trace appear at the right time and within a milliHz
of a confirmed and correctly calibrated frequency, I have hardly a doubtabout the validity of the reception. Even more so if the transmission ca= n be
verified by comparison to a calibrated grabber in another location= .

It seems that the G3KEV antenna does have excellent sensitivity at VLF= . It
would be fantastic if you could augment that with a stable, proper= ly
calibrated, and narrowband reception system. SpecLab has made that= so easy
now - throw out the wildly drifting "receiver", connect your ant= enna
directly to the soundcard instead, lock to one of your MSK neighbo= urs (GBZ
or GQD), and your in the game.

Best regards,
Markus= (DF6NM)


From: mal hamilton
Sent: Friday, March 11, 2011 5:57 PM
To:= rsgb
Subject: LF: VLF traces


I can see a couple of vy weak= traces around 8970 but this is no guarantee
who it might be because th= ere is no ID. Frequency alone is not a VALID
report- it could be anything.
G3KEV



<= br>

--00504502ecd539b1cc049e50ccfa--