Return-Path: X-Spam-DCC: paranoid 1290; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: * X-Spam-Status: No, score=1.1 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, FORGED_RCVD_HELO,HTML_40_50,HTML_MESSAGE,HTML_TINY_FONT,PLING_QUERY, SPF_PASS autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id uA46XbU4031062 for ; Fri, 4 Nov 2016 07:33:37 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1c2Xx2-0000DW-0e for rs_out_1@blacksheep.org; Fri, 04 Nov 2016 06:26:08 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1c2Xx1-0000DN-88 for rsgb_lf_group@blacksheep.org; Fri, 04 Nov 2016 06:26:07 +0000 Received: from smtpcmd0648.aruba.it ([62.149.156.48] helo=smtpcmd01229.aruba.it) by relay1.thorcom.net with esmtp (Exim 4.87) (envelope-from ) id 1c2Xww-00032g-0x for rsgb_lf_group@blacksheep.org; Fri, 04 Nov 2016 06:26:06 +0000 Received: from ik0vve.net ([62.149.158.90]) by smtpcmd06.ad.aruba.it with bizsmtp id 3iRz1u0011xJdJu01iRzpK; Fri, 04 Nov 2016 07:26:00 +0100 Date: Fri, 4 Nov 2016 07:25:59 +0100 Message-Id: In-Reply-To: <581B83FC.6060600@posteo.de> References: =?iso-8859-1?q?=3C581B3A1F=2E5060609=40posteo=2Ede=3E_=3Ce44cf075=2D7?= =?iso-8859-1?q?dd2=2D699b=2D6af3=2D656831b7c8df=40df3lp=2Ede=3E_=3C58?= =?iso-8859-1?q?1B83FC=2E6060600=40posteo=2Ede=3E?= MIME-Version: 1.0 X-Sensitivity: 3 From: "Max IK0VVE" To: rsgb_lf_group@blacksheep.org X-XaM3-API-Version: V3(R2) X-SenderIP: 212.66.105.4 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=aruba.it; s=a1; t=1478240760; bh=ir95BG2ShwvE3np0xf7K4vcpvE2bzGilOXXnvJvc1Lk=; h=Date:Subject:MIME-Version:Content-Type:From:To; b=A3inX9E9yHpbbNnkaSwQ815It9oSWNnajcgh2Bw3o3ptS9ERRdeNFZNlUBeTvHS7v v7gu7PdIHpLQ9c1t2HNvbbu7Ki0iQRP4PIUErocd9TwgmCAKO5EbBSRJHWDUEzlfIX 2pWUz5KPYmtpbHDAhDht+sepZqJvhGngknl39wJKBcPp6q9//lQdZ/bAkBGxwiVQ6K 6/4UjX8WyXVurcl4yn5T8XEoMpC6IPi7p4nBNsfHkfkRwVjhfXfni/8ZAFflsA/otr cHqCyJxTWJsHP/dILKxrrmqybbxfH9K0OZkmhdImpwLmCntHiIv1e1mKaC1y6qqV43 5yCcEgTtfsxWA== X-Scan-Signature: 567a11ac6cfe1e88f3054745c06178fe Subject: Re: LF: Smart noise cancelling?!? Content-Type: multipart/alternative; boundary="_=__=_XaM3_.1478240759.2A.689794.42.6333.52.42.007.354709621" 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-Scanned-By: MIMEDefang 2.56 on 10.1.3.11 Content-Length: 12478 Status: O X-Status: X-Keywords: X-UID: 9390 --_=__=_XaM3_.1478240759.2A.689794.42.6333.52.42.007.354709621 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Dear friends,=0A=0Ain the list there is an elite of eminent professionals= , so my participation to this post could sound like a cry of a newborn, H= I, but I would give my 1/2 =E2=82=ACcent to discussion.=C2=A0=0AAre about= 2 years that I receive strong noise from neighbour LED PS light, strong = means that I'm completely deaf from 0 to 150 MHz! The only real solution = I've found is the use of the X-phase killer with a little upgrade to bett= er work on MF and LF. Now I can hear your signals again, it works great.=0A= So thinking to VLF that is an "audio" frequency, could it be possible to = use the same principle and put the noise in 180=C2=B0 antiphase receiving= sferics with another RX some khz far (also a cheap LW radio) from main f= req as some noise cancelling headphones do?=C2=A0=0AProbably there is som= e problem that I didn't considered yet (band wide, delay, etc...)=0A=0ATh= anks to all.=0A=0A73, Max IK0VVE=C2=A0=0A=C2=A0=0A=C2=A0=0A=0A=0A________= ______________________=C2=A0...here some of my HAM Radio projects...SkyGe= M RotatorAntennaDinamicaRCR-DX=0Awww.ik0vve.net=0A=0A=0ADa: owner-rsgb_lf= _group@blacksheep.org=0AA: rsgb_lf_group@blacksheep.org=0ACc: =0AData: Th= u, 03 Nov 2016 19:37:48 +0100=0AOggetto: Re: LF: Smart noise cancelling?!= ?=0A=0A=0AHi Peter,=0A=C2=A0=0AThat sounds interesting and looks convinci= ng. But it only works for =0A'compressed' spectra covering several kHz an= d hours, right?=0A=C2=A0=0AAs far as i understand this method can't be do= ne for weak signal =0Adetections because you 'need' all the energy availa= ble from the weak =0Asignal to fill the bin (one pixel) and just throw aw= ay what causes a =0Areduction of the SNR, so just the stronger QRN bursts= are blanked and =0Amost of the signal is coming through whereas your met= hod selects just a =0Asmall fraction of the incoming energy (?).=0A=C2=A0= =0AMy idea/question came from the consideration that different kind of QR= N =0Ahas different optimum blanker settings.=0A=C2=A0=0AAm 02.11.2016 21:= 25, schrieb Paul Nicholson:=0A>=C2=A0=0A> Even more aggressive sferic bla= nking raises=0A> the decode to Eb/N0 +1.7 dB BER 38.2%=0A> S/N 16.10 dB i= n 25.4 uHz.=0A=C2=A0=0ASo, if propagation changes, the optimal blanker se= ttings will change. So =0Athey vary all the time. If a post-processing of= a transmission/recording =0Ataking several hours and night/day changes, = it could be useful to =0Adynamically vary the blanker settings. So these = blanker setting levels =0Awould have to be determined/calculated by the i= ncoming signal and then =0Aapplied in a next step.=0AThis may be CPU-load= intensive, i don't know, it's behind my current =0Askills. But the idea = is there...=0A=C2=A0=0A=C2=A0=0A73, Stefan=0A=C2=A0=0A=C2=A0=0AAm 03.11.2= 016 18:55, schrieb Peter:=0A> Hi Stefan et al.,=0A>=C2=A0=0A> On 03.11.20= 16 14:22, DK7FC wrote:=0A>> ...=0A>> Last night i thought a bit about noi= se cancelling on LF/VLF.=0A> > ...=0A>=C2=A0=0A> Running an experimental = receiver at VLF/LF for SID-detection (on RPi =0A> 3) I chose an almost no= n-parametric procedure running in frequency =0A> domain. It works as foll= ows:=0A> Do a windowed FFT, compute the median (by sorting) from the powe= r =0A> spectrum. Store all spectra and corresponding median values. Next = =0A> choose a time period (let's say 100ms), pick the spectrum with the =0A= > lowest median, plot it, drop all the others. The key is that "Median =0A= > values" are more robust to outliers compared to other averaging =0A> pr= ocedures.=0A>=C2=A0=0A> See what happened when switching from simple aver= aging to median =0A> selection algorithm (~16:50 utc):=0A> http://lf-radi= o.de/cgi-bin/test/show_wf.cgi?date=3D16-10-02=0A>=C2=A0=0A> I know that t= his won't work in case of searching for coherent signal =0A> detection, o= r would be hard to implement. But using this method I'm =0A> detecting su= ch very weak signals from far east like NDI or RTZ on a =0A> regular basi= s.=0A>=C2=A0=0A> Drawbacks? Yes; it's throwing away a lot of information = which may be =0A> useful. Another pitfall has to be mentioned: using 1 se= c. as a =0A> selection window strong time service transmitters nearly van= ished =0A> since the algorithm will unerringly choose the gaps [^_^]. The= refore =0A> I'm using only the spectral part between 15 and 50 kHz for co= mputing =0A> the median values.=0A>=C2=A0=0A> Peter, df3lp=0A>=C2=A0=0A=C2= =A0 --_=__=_XaM3_.1478240759.2A.689794.42.6333.52.42.007.354709621 Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable
Dear friends,=

in the list there is an elite of eminent professionals, so my par= ticipation to this post could sound like a cry of a newborn, HI, but I wo= uld give my 1/2 =E2=82=ACcent to discussion. 
Are about 2 years t= hat I receive strong noise from neighbour LED PS light, strong means that= I'm completely deaf from 0 to 150 MHz! The only real solution I've found= is the use of the X-phase killer with a little upgrade to better work on= MF and LF. Now I can hear your signals again, it works great.
So thin= king to VLF that is an "audio" frequency, could it be possible to use the= same principle and put the noise in 180=C2=B0 antiphase receiving sferic= s with another RX some khz far (also a cheap LW radio) from main freq as = some noise cancelling headphones do? 
Probably there is some prob= lem that I didn't considered yet (band wide, delay, etc...)

Thanks= to all.

73, Max IK0VVE 
 
 


______________________________

 
...here= some of my HAM Radio projects...



=0A
Da: owner-rsgb_lf_group@bl= acksheep.org
=0A
A: rsgb_lf_group@blacksheep.o= rg
=0A
Cc:
=0A
Data: Thu, 03 Nov 2016 19:37:48 +0100
=0A
Oggetto= : Re: LF: Smart noise cancelling?!?
=0A
=0A
Hi Peter,<= /div>
 
That sounds interesting and looks convincing. = But it only works for
'compressed' spectra covering several kH= z and hours, right?
 
As far as i understand thi= s method can't be done for weak signal
detections because you = 'need' all the energy available from the weak
signal to fill t= he bin (one pixel) and just throw away what causes a
reduction= of the SNR, so just the stronger QRN bursts are blanked and
m= ost of the signal is coming through whereas your method selects just a
small fraction of the incoming energy (?).
 
My idea/question came from the consideration that different kind of= QRN
has different optimum blanker settings.
 <= /div>
Am 02.11.2016 21:25, schrieb Paul Nicholson:
>&nbs= p;
> Even more aggressive sferic blanking raises
&= gt; the decode to Eb/N0 +1.7 dB BER 38.2%
> S/N 16.10 dB in = 25.4 uHz.
 
So, if propagation changes, the opti= mal blanker settings will change. So
they vary all the time. I= f a post-processing of a transmission/recording
taking several= hours and night/day changes, it could be useful to
dynamicall= y vary the blanker settings. So these blanker setting levels
w= ould have to be determined/calculated by the incoming signal and then
applied in a next step.
This may be CPU-load intensive,= i don't know, it's behind my current
skills. But the idea is = there...
 
 
73, Stefan
 
 
Am 03.11.2016 18:55, schrieb Peter:
> Hi Stefan et al.,
> 
> On 03.= 11.2016 14:22, DK7FC wrote:
>> ...
>> Las= t night i thought a bit about noise cancelling on LF/VLF.
> = > ...
> 
> Running an experimental rece= iver at VLF/LF for SID-detection (on RPi
> 3) I chose an al= most non-parametric procedure running in frequency
> domain= . It works as follows:
> Do a windowed FFT, compute the medi= an (by sorting) from the power
> spectrum. Store all spectr= a and corresponding median values. Next
> choose a time per= iod (let's say 100ms), pick the spectrum with the
> lowest = median, plot it, drop all the others. The key is that "Median
= > values" are more robust to outliers compared to other averaging
> procedures.
> 
> See what happ= ened when switching from simple averaging to median
> selec= tion algorithm (~16:50 utc):
> http://lf-radio.de/cgi-bin/te= st/show_wf.cgi?date=3D16-10-02
> 
> I know= that this won't work in case of searching for coherent signal
> detection, or would be hard to implement. But using this method I'm=
> detecting such very weak signals from far east like NDI = or RTZ on a
> regular basis.
> 
> Drawbacks? Yes; it's throwing away a lot of information which may b= e
> useful. Another pitfall has to be mentioned: using 1 se= c. as a
> selection window strong time service transmitters= nearly vanished
> since the algorithm will unerringly choo= se the gaps [^_^]. Therefore
> I'm using only the spectral = part between 15 and 50 kHz for computing
> the median value= s.
> 
> Peter, df3lp
> <= /div>
 
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