Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dg06.r1000.mx.aol.com (Internet Inbound) with ESMTP id 032A8380000EB; Tue, 28 Aug 2012 12:48:41 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1T6Owj-0003Vz-MX for rs_out_1@blacksheep.org; Tue, 28 Aug 2012 17:47:21 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1T6Owj-0003Vq-1B for rsgb_lf_group@blacksheep.org; Tue, 28 Aug 2012 17:47:21 +0100 Received: from smtpout4.wanadoo.co.uk ([80.12.242.68] helo=smtpout.wanadoo.co.uk) by relay1.thorcom.net with esmtp (Exim 4.77) (envelope-from ) id 1T6Owg-00076g-1X for rsgb_lf_group@blacksheep.org; Tue, 28 Aug 2012 17:47:19 +0100 Received: from AGB ([2.26.21.90]) by mwinf5d59 with ME id sGnF1j02f1wcuYa03GnGiW; Tue, 28 Aug 2012 18:47:16 +0200 Message-ID: <24067C8AEE7D47088C54E354FE436A6E@AGB> From: "Graham" To: References: <1067FFBBAFB14287AD6D816189F51B78@White> <004d01cd8529$0baa83d0$0501a8c0@xphd97xgq27nyf> In-Reply-To: <004d01cd8529$0baa83d0$0501a8c0@xphd97xgq27nyf> Date: Tue, 28 Aug 2012 17:47:15 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal Importance: Normal X-Mailer: Microsoft Windows Live Mail 14.0.8117.416 X-MimeOLE: Produced By Microsoft MimeOLE V14.0.8117.416 X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has identified this incoming email as possible spam. The original message has been attached to this so you can view it (if it isn't spam) or label similar future email. If you have any questions, see the administrator of that system for details. Content preview: Interesting analogy Mal ! may be we should start a CFRD group , Campaign For Real Data ? you can the 'KEY' person : ) G.. From: mal hamilton Sent: Tuesday, August 28, 2012 3:22 PM To: rsgb_lf_group@blacksheep.org Subject: LF: Re: WD2XES - Opera detected and identified by correlation [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [80.12.242.68 listed in list.dnswl.org] 0.0 HTML_MESSAGE BODY: HTML included in message X-Scan-Signature: ce3df9f2acd7587159138e0455ceb9aa Subject: Re: LF: Re: WD2XES - Opera detected and identified by correlation Content-Type: multipart/alternative; boundary="----=_NextPart_000_0091_01CD8545.2981EA30" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.6 required=5.0 tests=HTML_20_30,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-sid: 3039ac1d410e503cf669746a X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_0091_01CD8545.2981EA30 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Interesting analogy Mal ! may be we should start a CFRD = group , Campaign For Real Data ? you can the 'KEY' person : )=20 G.. From: mal hamilton=20 Sent: Tuesday, August 28, 2012 3:22 PM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: Re: WD2XES - Opera detected and identified by correlation Markus This is what the CW es QRS operator are already doing. They have a list = of known operators Callisgns and a mental list of what the text is going = to be, like RST, OOO, MMM etc, Names, QRA locator etc. If a piece of = callsign or text fades out in QSB or hit by QRN then it is easy to = insert the missing digit. In other words what is being received is being compared against already = known information should it become necessary to use it. This works on LF because of the few operators on the band but would not = work on HF where there are hundreds of callsigns to pick from. mal/g3kev ----- Original Message -----=20 From: Markus Vester=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Monday, August 27, 2012 10:22 PM Subject: LF: WD2XES - Opera detected and identified by correlation Recently I have been pondering wether it is possible to detect QRSS or = Opera transmissions by signal correlation against a known waveform. This = should far be more sensitive than the conventional incoherent decoding = process. John's stable and phase-coherent Opera transmission last = night's provided a welcome opportunity to test this scheme. Using SndInput from DL4YHF, I recorded a long IQ file at 2 samples / = second, ie. 2 Hz wide centered on 137561 Hz. The audio was taken = straight from the Rubidium-locked receiver, with no noise blanking = inserted. The data was then postprocessed using a MathCad spreadsheet. = Some results can be viewed in=20 http://df6nm.bplaced.net/opera/xes/ , along with TA grabber screenshots showing both XGJ and a weak trace = from XES in 21 mHz FFT (testTA.jpg). First a high resolution spectrogram was generated, at 1.9 mHz per bin = (xes_spectrogram.png). The central carrier component of the transmission = can clearly be seen. Best SNR occured between 3:30 and 4:30 UT (as = indicated by marker ticks), when the peak was 9.0 dB above the noise = (xes_spectrum.png). Scaling noise bandwidth from 2.9 mHz to 2.5 kHz = (-49.5 dB), and adding 6 dB for 50% duty cycle, we get a peak-power SNR = of -44.5 dB. This corresponds to -48.5 dB on the Opera SNR scale, about = 9 dB below the current decoding threshold for Op-32. The peak appeared about 0.2 Hz off-center because the 12 kHz = samplerate had not been not calibrated. Once the peak frequency is = accurately identified, the received signal can be correlated against a = "prototype" waveform, which contains the Opera sequence for WD2XES, = 16-fold oversampled. The correlation is efficiently implemented as a = multiplication in Fourier space. The result (xes_correlation_wd2xes.png) shows four distinct peaks in = time domain at 2:15, 2:48, 3:21 and 3:54 UT, which should correspond to = the a-priori unknown start times of John's Opera sequences. The = repetition period was apparently 32.92 minutes. As the DC component in = the reference waveform had not been removed, the peaks are riding on a = pedestal caused by the self-correlation of the carrier component. To check the ability to identify an unknown station, the correlation = to a different callsign was also plotted (WD2XGJ just as an arbitrary = example, see xes_correlation_wrongcode). In spite of the weak = cross-correlation peaks, we find that a correct selection from a list of = potential candidates would certainly be feasible. It would not be too difficult to automate this process and create an = "Opera deep search" software, which should be able to detect and = identify signals reliably down to about 12 dB below the threshold of the = current Opera decoder. This means at same sensitivity we could go 16 = times faster!=20 To reap this benefit, the following prerequisits need to be fulfilled: - As we need a carrier component, transmit keying has to be phase = coherent. Thus simple keying schemes which interrupt the oscillator or = divider would not work. - as we look at phase-sensitive integration over the whole sequence = rather than a single symbol duration, the frequency stability has to be = much tighter. - As there is no bit-wise decoding involved, we will need to supply a = list of potential candidate callsigns (similar to deep-search in K1JT = EME modes). Thanks again to John and Warren for the signals! Best 73, Markus=20 (DF6NM in JN59NJ) ------=_NextPart_000_0091_01CD8545.2981EA30 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
Interesting   analogy  Mal !  may   = be =20 we  should  start  a  CFRD   group ,=20 Campaign  For  Real  Data ? you  can  the  = 'KEY'   person : )
 
G..

From: mal hamilton
Sent: Tuesday, August 28, 2012 3:22 PM
Subject: LF: Re: WD2XES - Opera detected and identified by=20 correlation

Markus
This is what the CW es QRS operator are already = doing.=20 They have a list of known operators Callisgns and a mental list of what = the text=20 is going to be,   like RST, OOO, MMM etc, Names, QRA = locator etc.=20 If a piece of callsign or text fades out in QSB or hit by=20 QRN then it is easy to insert the = missing digit.
In other words what is being received is being = compared=20 against already known information should it become necessary to use = it.
This works on LF because of the few operators on = the band=20 but would not work on HF where there are hundreds of callsigns to pick=20 from.
mal/g3kev
 
----- Original Message -----
From:=20 Markus=20 Vester
Sent: Monday, August 27, 2012 = 10:22=20 PM
Subject: LF: WD2XES - Opera = detected and=20 identified by correlation

Recently I have been pondering wether = it is=20 possible to detect QRSS or Opera transmissions by signal correlation = against a=20 known waveform. This should far be more sensitive than the = conventional=20 incoherent decoding process. John's stable and phase-coherent Opera=20 transmission last night's provided a welcome opportunity to test this=20 scheme.
 
Using SndInput from DL4YHF, I = recorded a long IQ=20 file at 2 samples / second, ie. 2 Hz wide centered on 137561 Hz. The = audio was=20 taken straight from the Rubidium-locked receiver, with no noise = blanking=20 inserted. The data was then postprocessed using a MathCad spreadsheet. = Some=20 results can be viewed in
http://df6nm.bplaced.net/ope= ra/xes/=20 ,
along with TA grabber screenshots showing both XGJ and a weak = trace from=20 XES in 21 mHz FFT (testTA.jpg).
 
First a high resolution spectrogram = was=20 generated, at 1.9 mHz per bin (xes_spectrogram.png). The central = carrier=20 component of the transmission can clearly be seen. Best SNR occured = between=20 3:30 and 4:30 UT (as indicated by marker ticks), when the peak was 9.0 = dB=20 above the noise (xes_spectrum.png). Scaling noise bandwidth from 2.9 = mHz to=20 2.5 kHz (-49.5 dB), and adding 6 dB for 50% duty cycle, we get a = peak-power=20 SNR of -44.5 dB. This corresponds to -48.5 dB on the Opera SNR scale, = about 9=20 dB below the current decoding threshold for Op-32.
 
The peak appeared about 0.2 Hz = off-center because=20 the 12 kHz samplerate had not been not calibrated. Once the peak = frequency is=20 accurately identified, the received signal can be correlated against a = "prototype" waveform, which contains the Opera sequence for WD2XES, = 16-fold=20 oversampled. The correlation is efficiently implemented as a = multiplication in=20 Fourier space.
 
The result = (xes_correlation_wd2xes.png) shows=20 four distinct peaks in time domain at 2:15, 2:48, 3:21 and 3:54 UT, = which=20 should correspond to the a-priori unknown start times of John's Opera=20 sequences. The repetition period was apparently 32.92 minutes. As the = DC=20 component in the reference waveform had not been removed, the peaks = are riding=20 on a pedestal caused by the self-correlation of the carrier=20 component.
 
To check the ability to identify an = unknown=20 station, the correlation to a different callsign was also plotted = (WD2XGJ just=20 as an arbitrary example, see xes_correlation_wrongcode). In spite of = the weak=20 cross-correlation peaks, we find that a correct selection from a list = of=20 potential candidates would certainly be feasible.
 
It would not be too difficult to = automate this=20 process and create an "Opera deep search" software, which should be = able to=20 detect and identify signals reliably down to about 12 dB below the = threshold=20 of the current Opera decoder. This means at same sensitivity  we = could go=20 16 times faster!
 
To reap this benefit, the following = prerequisits=20 need to be fulfilled:
- As we need a carrier component, transmit = keying has=20 to be phase coherent. Thus simple keying schemes which interrupt the=20 oscillator or divider would not work.
- as we look at = phase-sensitive=20 integration over the whole sequence rather than a single symbol = duration, the=20 frequency stability has to be much tighter.
- As there is no = bit-wise=20 decoding involved, we will need to supply a list of potential = candidate=20 callsigns (similar to deep-search in K1JT EME modes).
 
Thanks again to John and Warren for = the=20 signals!
 
Best 73,
 
Markus
(DF6NM in=20 JN59NJ)
 
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