Return-Path: X-Spam-DCC: paranoid 1170; Body=3 Fuz1=3 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_30_40,HTML_MESSAGE 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 tA1K0f6k014896 for ; Sun, 1 Nov 2015 21:00:41 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1Zsykh-0004aC-St for rs_out_1@blacksheep.org; Sun, 01 Nov 2015 19:57:19 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1Zsykh-0004a3-Ep for rsgb_lf_group@blacksheep.org; Sun, 01 Nov 2015 19:57:19 +0000 Received: from mail-wm0-f46.google.com ([74.125.82.46]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1Zsyjd-0006tA-BJ for rsgb_lf_group@blacksheep.org; Sun, 01 Nov 2015 19:57:18 +0000 Received: by wmeg8 with SMTP id g8so44316887wme.0 for ; Sun, 01 Nov 2015 11:55:57 -0800 (PST) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=2L21WSyzwi5vVGiaj6TwHHpeCJCMcF3sBqxjtUtCWlU=; b=QEdSUWT+9C5x7O/cm2uoOQzbZzOFiVlRTlbIgSf1+9a1iLg/e+8bLh9+NKb6PvA60d BvsfokurZS9cdqiJmioLY3lT7JNlUHkh8RcoDHZmvexaP+eF9KipR6y65A4gXJ3Fiz0X 8+NW0yF2TxbKbWzPHCtzj8Ue19YKRw18SUDaVJXel16n1ldIpePrrHDT6lqd6H5NJ8PQ 5KrmCwLgiA9qfq02Gg7ABm6qVzF4/VljDpip/l50jtOV5i65bIhFQ4woIPNX3bN2w35z IaM8doNaZd9uJ99S4BhGxWLnemqGW+Ip0O6SdyYWrlRST0G7Ai/6W7nYPqRvWMweCPBe fHkg== MIME-Version: 1.0 X-Received: by 10.28.12.142 with SMTP id 136mr9132800wmm.19.1446407757545; Sun, 01 Nov 2015 11:55:57 -0800 (PST) Received: by 10.28.183.139 with HTTP; Sun, 1 Nov 2015 11:55:57 -0800 (PST) In-Reply-To: <85196BC78CF6472CAFCDEB70A7BFD6A7@gnat> References: <56365650.1080701@gmail.com> <85196BC78CF6472CAFCDEB70A7BFD6A7@gnat> Date: Sun, 1 Nov 2015 19:55:57 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Scan-Signature: 9384a33da03ada6d15116c61d7d30153 Subject: Re: LF: RTE 252kHz Content-Type: multipart/alternative; boundary=001a1144435096c6290523800ca7 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 10.1.3.10 Status: O X-Status: X-Keywords: X-UID: 4773 --001a1144435096c6290523800ca7 Content-Type: text/plain; charset=UTF-8 Yes, I think its the VE2ZAZ GPSDO here. MSF was showing 0.6PPB frequency error too, so defintely the reference source I'm recalling that when tested before it was out by that sort of order - its an odd beast, a frequency counter that prods the OCXO periodically. Very long settling times. I've just fired up an old Connor Winfield GPSDO . That's the short time constant type of GPSDO, so ideal for LF use with long symbol periods. Andy On 1 November 2015 at 19:39, Alan Melia wrote: > Hi Andy I havent checked recently but as far as I know NPL measure > Droitwich twice a day and post the tabulated results on their web site.If > they see a problem they contact the contractor (was Merlin Communications) > and a man gets on his bike from Coventry :-)). After my reports and the > subsequent synth failure a number of years back I think Merlin, slightly > embarassed bought themselves an off-air standard. 0.6ppb is well inside the > level that would get NPL ringing Merlin but the "apparent reflection > height" may still be rising at 1900z?? > > Alan > G3NYK > > ----- Original Message ----- > *From:* Andy Talbot > *To:* rsgb_lf_group@blacksheep.org ; rsgb_lf_group@yahoogroups.co.uk > *Sent:* Sunday, November 01, 2015 7:00 PM > *Subject:* Re: LF: RTE 252kHz > > Hi All - > > Its no good at this stage looking for small signals. All I'm trying to do > is prove the HARDWARE. At the moment I have a QSD type receiver delivering > a signal centred on 1kHz. This is bandpass filtered to about 100Hz > bandwidth, then I/Q sampled at 1kHz sampling rate to deliver 12 bit > baseband values at 1kHz > > At the moment all I'm doing with these is displaying them on a > vectorscope plot - like that shown in the attachment - in order to prove > phase coherency of the system. So only strong signals are acceptable at > this stage - decimation and narrowband filtering can come later - that is > high level software and easier to implement > > And I've discovered something that needs explaining. Having just been > monitoring Droitwich on 198kHz for the last couple of hours, its phase plot > indicates drift of 300 degrees in that time. Expressed in terms of a > frequency offset that is 0.00012Hz, or 0.6 PPB at 198kHz. > > Now : > My reference is a VE2ZAZ GPSDO which is long term spot on, but subject to > short term variations. I have to check if it remains better than 0.6PPB > over that period. The VE2ZAZ isn't my favourite solution for LF > working. But a local high standard frequency reference isn't an issue - > the Caesium tube can be turned on to solve that one! > > The LO in the LF receiver is a DDS tuned by a rotary encoder. The PIC > maths was written from first principles using 64 x 64 bit integer > arithmetic, BUT the pre-stored -constants to start with were evaluated via > a spreadsheet - which I'm not convinced provides sufficient numerical > accuracy to simulate the maths resolution needed to get teh constantsin teh > first place. So that needs checking. > > And, of course, although Droitwich is supposed to be a frequency > standard, it is only Rubidium controlled; set manually from "time to time" > against an on site Caesium source. 0.6 PPB is of the order of a Rb source > that hasn't been corrected for a while. Is Droitwich properly maintained > these days when very few people want it as a reference? can we really > assume its good enough? > > I've now changed to monitoring MSF 60kHz so lets see what indicted drift > that shows - its reasonable to assume that really is good! > > Checking the constants used in the arithmetic is the most difficult task. > My high level programming language only offer up to 64 bit integers, so the > multiplication used in the PIC cannot be simulated exactly in a prog, > meaning I need to work with double precision floats and cast to integers as > and when. > > Andy G4JNT > > On 1 November 2015 at 18:13, IZ7SLZ wrote: > >> On 11/1/2015 4:17 PM, Andy Talbot wrote: >> >>> Oh well... >>> >>> Still searching for a clean MF carrier >>> >>> Andy G4JNt >>> >>> >> Hello Andy, and all >> >> i'm now putting a small signal on 478502.24 Hz in opera8 mode. Tx is >> GPS-locked. It is the same TX exciter that i used in EbNaut experiment >> weeks ago. >> Maybe this signal is useful for your receiver test. >> >> All the best. >> >> 73, Domenico / iz7slz >> >> > --001a1144435096c6290523800ca7 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
Yes, I think its the VE2ZAZ GPSDO here. =C2=A0 MSF was sho= wing 0.6PPB frequency error too, so defintely the reference source
=C2= =A0I'm recalling that when tested before it was out by that sort of ord= er - its an odd beast, a frequency counter that prods the OCXO periodically= . =C2=A0 Very long settling times. =C2=A0=C2=A0

I've= just fired up an old Connor Winfield GPSDO .=C2=A0 That's the short ti= me constant type of GPSDO, so ideal for LF use with long symbol periods.

Andy


On 1 November 2015 at 19:39, Ala= n Melia <alan.melia@btinternet.com> wrote:
Hi Andy I havent checked recently but = as far as I=20 know NPL measure Droitwich twice a day and post the tabulated results on th= eir=20 web site.If they see a problem they contact the contractor (was Merlin=20 Communications) and a man gets on his bike from Coventry :-)). After my rep= orts=20 and the subsequent synth failure a number of years back I think Merlin, sli= ghtly=20 embarassed bought themselves an off-air standard. 0.6ppb is well inside the= =20 level that would get NPL ringing Merlin but the "apparent reflection h= eight" may=20 still be rising at 1900z??
=C2=A0
Alan
G3NYK
----- Original Message -----
From:=20 Andy=20 Talbot
Sent: Sunday, November 01, 2015 7:0= 0=20 PM
Subject: Re: LF: RTE 252kHz

Hi All -=C2=A0

Its no good at this stage looking for small signals.=C2=A0 All I'= ;m trying=20 to do is prove the HARDWARE.=C2=A0 At the moment I have a QSD type receiv= er=20 delivering a signal centred on 1kHz. =C2=A0 =C2=A0This is bandpass filter= ed to=20 about 100Hz bandwidth, then I/Q sampled at 1kHz sampling rate to deliver = 12=20 bit baseband values at 1kHz

At the moment all I'm doing with these is =C2=A0displaying them = on a=20 vectorscope plot - like that shown in the attachment - in order to prove = phase=20 coherency of the system.=C2=A0 So only strong signals are acceptable at t= his=20 stage - decimation and narrowband filtering can come later - that is high= =20 level software and easier to implement

And I've discovered something that needs explaining.=C2=A0 Havin= g just=20 been monitoring Droitwich on 198kHz for the last couple of hours, its pha= se=20 plot indicates drift of 300 degrees in that time. =C2=A0 Expressed in ter= ms of=20 a frequency offset that is 0.00012Hz, or 0.6 PPB at 198kHz.

Now :
My reference is a VE2ZAZ GPSDO which is long term spot on, but subje= ct to=20 short term variations. =C2=A0 I have to check if it remains better than 0= .6PPB=20 over that period. =C2=A0 =C2=A0The VE2ZAZ isn't my favourite solution= for LF=20 working.=C2=A0 But a local high standard frequency reference isn't an= issue -=20 the Caesium tube can be turned on to solve that one!

The LO in the LF receiver is a DDS tuned by a rotary encoder. =C2=A0= =20 =C2=A0The PIC maths was written from first principles using 64 x 64 bit= =20 integer arithmetic, BUT the pre-stored -constants to start with were eval= uated=20 via a spreadsheet - which I'm not convinced provides sufficient numer= ical=20 accuracy to simulate the maths resolution needed to get teh constantsin t= eh=20 first place. =C2=A0 So that needs checking.

And, of course, =C2=A0 although Droitwich is supposed to be a freque= ncy=20 standard, it is only Rubidium controlled; set manually from "time to= time"=20 against an on site Caesium source. =C2=A00.6 PPB is of the order of a Rb= =20 source that hasn't been corrected for a while. =C2=A0 Is Droitwich pr= operly=20 maintained these days when very few people want it as a reference? =C2=A0= can=20 we really assume its good enough?

I've now changed to monitoring MSF 60kHz so lets see what indict= ed drift=20 that shows - its reasonable to assume that really is good!

Checking the constants used in the arithmetic is the most difficult= =20 task.=C2=A0 My high level programming language only offer up to 64 bit=20 integers, so the multiplication used in the PIC cannot be simulated exact= ly in=20 a prog, meaning I need to work with double precision floats and cast to= =20 integers as and when.

Andy =C2=A0G4JNT

On 1 November 2015 at 18:13, IZ7SLZ <iz7slz.domenico@gmail.com> wrote:
On 11/1/2015 4:17 PM, Andy Talbot w= rote:
Oh well...

Still searching= for a clean MF=20 carrier

Andy=C2=A0 =C2=A0G4JNt


Hello A= ndy,=20 and all

i'm now putting a small signal on 478502.24 Hz in op= era8=20 mode. Tx is GPS-locked. It is the same TX exciter that i used in EbNaut= =20 experiment=C2=A0 weeks ago.
Maybe this signal is useful for your rec= eiver=20 test.

All the best.

73, Domenico /=20 iz7slz



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