Return-Path: X-Spam-DCC: paranoid 1170; 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=-1.9 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_40_50,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 tA28CQED019434 for ; Mon, 2 Nov 2015 09:12:26 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1ZtA6f-0005zZ-Ud for rs_out_1@blacksheep.org; Mon, 02 Nov 2015 08:04:45 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1ZtA6X-0005zQ-HJ for rsgb_lf_group@blacksheep.org; Mon, 02 Nov 2015 08:04:37 +0000 Received: from mail-wi0-f174.google.com ([209.85.212.174]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1ZtA5T-0008Ss-8a for rsgb_lf_group@blacksheep.org; Mon, 02 Nov 2015 08:04:36 +0000 Received: by wicfv8 with SMTP id fv8so44745066wic.0 for ; Mon, 02 Nov 2015 00:03:17 -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=QrCXbaOpoc7ZvxpjchyNUj4M0TzIRxlnUhPr3tVeSCs=; b=K+p35ze/7qUVfO1bZNSc+8KSEKkR1nlgx5qhrdoUmd2zH2Zu54wirzBepKoi6GgZHd 8BscIowSQjHqSSuV2GX7PSrb6y2os1h2Gauh1uF5+zJmE8pM3JxMqVZnq/San1BstQMO TAOEI/FrmRupz1AdCGxNq2eWccruFH5TGO5/0rqPdtvZVVIyhjbj0k8YY1IFHqe+s/mn BldD0JVcp/gopQlv0DeEmtwxjwTBf6TURha5EUo/P7VLALSB/J3fowGeLR6cEXOk6TW7 Hq8Sl/v5k8V7joq/tTlIx+ctIw6Tm6+tO3zfUuyOWrGHGgkBfDs28jiFbsDxEq6bpw2x RNdQ== MIME-Version: 1.0 X-Received: by 10.194.62.15 with SMTP id u15mr24129557wjr.18.1446451397552; Mon, 02 Nov 2015 00:03:17 -0800 (PST) Received: by 10.28.183.139 with HTTP; Mon, 2 Nov 2015 00:03:17 -0800 (PST) In-Reply-To: References: <56365650.1080701@gmail.com> <85196BC78CF6472CAFCDEB70A7BFD6A7@gnat> Date: Mon, 2 Nov 2015 08:03:17 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Scan-Signature: c61917eaf8bc8733d7e85540486fff22 Subject: Re: LF: RTE 252kHz Content-Type: multipart/alternative; boundary=047d7ba9750abc6f7605238a35c5 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: 4781 --047d7ba9750abc6f7605238a35c5 Content-Type: text/plain; charset=UTF-8 That's the one advantage of the 'ZAZ. As it uses a decent OCXO, its short term stability is excellent, unfortunately not the main requirement for LF use ,but great for microwaves Andy On 1 November 2015 at 21:58, Alan Melia wrote: > Hi Andy, maybe or maybe not. I did detect a "breathing effect" of a few > parts in 10^11 soon after the synth was replaced at Droitwich. At this > level I was not sure of my own stadard's stability which was a pair > of Austron 1250a DOCXOs which have a short term stability of 1in 10^12 0ver > a couple of minutes. > > Well the 'ZAZ is a FLL not a PLL :-)) > > Alan > G3NYK > > > ----- Original Message ----- > *From:* Andy Talbot > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Sunday, November 01, 2015 9:07 PM > *Subject:* Re: LF: RTE 252kHz > > Confirmed. > After 70 minutes of using the other GPSDO, the phase display of Droitwich > has remained in the same place - so subject to phase reading accuracy, that > is a frequency accuracy of a part or two in 10^-11 - much more like it! > > In fact, watching over a period of several minutes, its poorer short term > stability can be seen as small phase shifts that reverse back over a few > minutes - although that could also be caused by propagation, perhaps ??? > > So the VE2ZAZ does need some doctoring and checking out - or scrapping. > > 'jnt > > > > > > On 1 November 2015 at 19:55, Andy Talbot wrote: > >> 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 >>>> >>>> >>> >> > --047d7ba9750abc6f7605238a35c5 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
That's the one advantage of the 'ZAZ.=C2=A0 A= s it uses a decent OCXO, its short term stability is excellent, unfortunate= ly not the main requirement for LF use ,but great for microwaves
=
Andy


=
On 1 November 2015 at 21:58, Alan Melia <alan.melia@btinternet.com> wrote:
Hi Andy, maybe or maybe not. I did det= ect a=20 "breathing effect" of a few parts in 10^11 soon after the synth w= as replaced at=20 Droitwich.=C2=A0At this level I was not sure of my own stadard's stabil= ity which=20 was a pair of=C2=A0Austron 1250a DOCXOs which have a short term stability o= f 1in=20 10^12 0ver a couple of minutes.
=C2=A0
Well the 'ZAZ is a FLL not a PLL := -))
=C2=A0
Alan
G3NYK
=C2=A0
----- Original Message -----
From:=20 Andy=20 Talbot
Sent: Sunday, November 01, 2015 9:07=20 PM
Subject: Re: LF: RTE 252kHz

Confirmed.
After 70 minutes of using the other GPSDO, the phase display of Droi= twich=20 has remained in the same place - so subject to phase reading accuracy, th= at is=20 a frequency accuracy of a =C2=A0part or two in 10^-11 - much more like it= !=20 =C2=A0

In fact, watching over a period of several minutes, its poorer short= term=20 stability can be seen as small phase shifts that reverse back over a few= =20 minutes - although that could also be caused by propagation, perhaps ???<= /div>

So the VE2ZAZ does need some doctoring and checking out - or=20 scrapping.

'jnt





On 1 November 2015 at 19:55, Andy Talbot <= andy.g4jnt@gmail.com> wrote:
Yes, I think its the VE2ZAZ GPSDO here. =C2=A0 MSF was= showing=20 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=20 order - its an odd beast, a frequency counter that prods the OCXO=20 periodically. =C2=A0 Very long settling times. =C2=A0=C2=A0

I've just fired up an old Connor Winfield GPSDO .=C2=A0 That&#= 39;s the=20 short time constant type of GPSDO, so ideal for LF use with long symbol= =20 periods.

Andy


On 1 November 2015 at 19:39, Alan Melia <alan.melia@btinternet.com> wrote:
Hi Andy I havent checked recentl= y but as far=20 as I know NPL measure Droitwich twice a day and post the tabulated re= sults=20 on their web site.If they see a problem they contact the contractor (= was=20 Merlin Communications) and a man gets on his bike from Coventry :-)).= =20 After my reports and the subsequent synth failure a number of years b= ack I=20 think Merlin, slightly embarassed bought themselves an off-air standa= rd.=20 0.6ppb is well inside the level that would get NPL ringing Merlin but= the=20 "apparent reflection height" may still be rising at 1900z??=
=C2=A0
Alan
G3NYK
----- Original Message -----
Sent: Sunday, November 01, 2015=20 7:00 PM
Subject: Re: LF: RTE 252kHz

Hi All -=C2=A0=20

Its no good at this stage looking for small signals.=C2=A0 All= I'm=20 trying to do is prove the HARDWARE.=C2=A0 At the moment I have a QS= D=20 type receiver delivering a signal centred on 1kHz. =C2=A0 =C2=A0Thi= s is=20 bandpass filtered to about 100Hz bandwidth, then I/Q sampled at 1kH= z=20 sampling rate to deliver 12 bit baseband values at 1kHz

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

And I've discovered something that needs explaining.=C2=A0= Having=20 just been monitoring Droitwich on 198kHz for the last couple of hou= rs,=20 its phase plot indicates drift of 300 degrees in that time. =C2=A0= =20 Expressed in terms of a frequency offset that is 0.00012Hz, or 0.6 = PPB=20 at 198kHz.

Now :
My reference is a VE2ZAZ GPSDO which is long term spot on, but= =20 subject to short term variations. =C2=A0 I have to check if it rema= ins=20 better than 0.6PPB over that period. =C2=A0 =C2=A0The VE2ZAZ isn= 9;t my=20 favourite solution for LF working.=C2=A0 But a local high standard= =20 frequency reference isn't an issue - the Caesium tube can be tu= rned on=20 to solve that one!

The LO in the LF receiver is a DDS tuned by a rotary encoder.= =20 =C2=A0 =C2=A0The PIC maths was written from first principles using = 64 x=20 64 bit integer arithmetic, BUT the pre-stored -constants to start w= ith=20 were evaluated via a spreadsheet - which I'm not convinced prov= ides=20 sufficient numerical accuracy to simulate the maths resolution need= ed to=20 get teh constantsin teh first place. =C2=A0 So that needs=20 checking.

And, of course, =C2=A0 although Droitwich is supposed to be a= =20 frequency standard, it is only Rubidium controlled; set manually fr= om=20 "time to time" against an on site Caesium source. =C2=A00= .6 PPB is of=20 the order of a Rb source that hasn't been corrected for a while= . =C2=A0=20 Is Droitwich properly maintained these days when very few people wa= nt it=20 as a reference? =C2=A0can we really assume its good enough?

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

Checking the constants used in the arithmetic is the most diff= icult=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= =20 exactly in a prog, meaning I need to work with double precision flo= ats=20 and cast to 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 wrote:
Oh well...

Still searching for a clean MF= =20 carrier

Andy=C2=A0 =C2=A0G4JNt


H= ello=20 Andy, and all

i'm now putting a small signal on 478502= .24 Hz in=20 opera8 mode. Tx is GPS-locked. It is the same TX exciter that i u= sed=20 in EbNaut experiment=C2=A0 weeks ago.
Maybe this signal is use= ful=20 for your receiver test.

All the best.

73, Domenico = /=20 iz7slz





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