Return-Path: X-Spam-DCC: paranoid 1102; 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=0.1 required=5.0 tests=ADVANCE_FEE_1,BAYES_00, DNS_FROM_AHBL_RHSBL,HTML_50_60,HTML_MESSAGE,HTML_TINY_FONT 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 tB9CK4pi003299 for ; Wed, 9 Dec 2015 13:20:04 +0100 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1a6dfi-0003SX-FM for rs_out_1@blacksheep.org; Wed, 09 Dec 2015 12:16:38 +0000 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1a6dfh-0003SJ-NV for rsgb_lf_group@blacksheep.org; Wed, 09 Dec 2015 12:16:37 +0000 Received: from mail-wm0-f50.google.com ([74.125.82.50]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.86) (envelope-from ) id 1a6dej-0005Hh-CC for rsgb_lf_group@blacksheep.org; Wed, 09 Dec 2015 12:16:36 +0000 Received: by wmuu63 with SMTP id u63so219608553wmu.0 for ; Wed, 09 Dec 2015 04:15:25 -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 :cc:content-type; bh=rHehaeCRDlpn7kFhbd8Nm/+uPnWUzfGYEYNW4xmzXVE=; b=Ey/1yBGj/lrqb2OAREsxJUml9HNxIzS3vVOElehiWOPmIZTSutXQbLDrDYgIcOk1G/ IcW1tIKBP/wLnXYd8nQWXsbJPoaEsK0mLoysmzHcVPB91usCiHc5xDU2nt4ufo1Hd23Z RfSJ/ojJtj7Pvx1TT2LloI9KlIJ2jqmnVQIIBQiAx9YbF4EXBe7yxXOKS7V3K4tcbJ8L J/VV85AhTPOUkyCoxhv9ooCJt7s/XXCFtinR0Whe8F0cQx/WU3t6K3n1moB3HJHOwVqX w5r4YdZB51cyIlzCfgUebycAozp43S7UTAsRzWfoEnI1Jzj2EtFaZV2dTznwPA/ji4g5 Evdg== MIME-Version: 1.0 X-Received: by 10.194.87.170 with SMTP id az10mr5409806wjb.144.1449663325082; Wed, 09 Dec 2015 04:15:25 -0800 (PST) Received: by 10.28.130.139 with HTTP; Wed, 9 Dec 2015 04:15:25 -0800 (PST) In-Reply-To: References: Date: Wed, 9 Dec 2015 12:15:25 +0000 Message-ID: From: Andy Talbot To: rsgb_lf_group@yahoogroups.co.uk Cc: rsgb_lf_group@blacksheep.org X-Scan-Signature: 308750728855677e0aa256742a73dd94 Subject: Re: [rsgb_lf_group] Re:: Fwd: LF: Frequency References GPSDOs etc. (was EbNaut etc...) Content-Type: multipart/alternative; boundary=089e010d867c891e4a0526760bd3 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: 5684 --089e010d867c891e4a0526760bd3 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable What is needed is a design for a homebrew 1 PPS *PHASE LOCKED* source. Both the Brooks Shera and VE2ZAZ designs are frequency locked loops - although it could be argued that frequency and phase are the same things, and it is the order of the PLL that is different. But whatever... they give noticeable errors short to medoium term Commercially quite low cost GPSDOs, like one I have from [what used to be] Connor Winfield give results that when averaged over a few minutes are quite accpetable in terms of absolute accuracy, and are in the sub-PPB region over shorter periods. The paper on my web site, URL given in a previous post, shows the CWin GPSDO short term stability. Those low end units use what would appear to be phase locking, and I see no reason why a simple edge triggered phase detector at 1PPS, using high speed logic couldn't be made to work. Problems ion the past have centred round phase detectors being not very useful when asked to deal with difference in tens of ns, but these days, one made using VHF logic or a gate array ought to be able to manage. I don't think an XOR phase detector is feasible, the filtering to get rid of the 2Hz residue, even at very long time constants, would be too much. Getting a real long time constant could be a bit of a headache without going into DSP, but good quality non electrolytics are around for several uF, and if we're not worried by size, several in || to say 50uFm with 20M resistors around CMOS opamps ought to be good enough - that's up to 20 minutes time constant and in the realm of needing an OCXO as the 10MHz source. Construction would need care to avaoid leakage though. My MSF reference way-back-when used CR values of this sort of value, and it did mostly work. Phase changes of RF due to proximity effects around he ferrite rod were its major downfall. And all the rest is just basic division On 9 December 2015 at 02:54, g8lco10@yahoo.co.uk [rsgb_lf_group] < rsgb_lf_group@yahoogroups.co.uk> wrote: > > > It is a not insignificant fact that Caesium Clocks are very expensive and > have finite lives as their caesium "fill" moves from the source end to th= e > ioniser. Current HP 5071's have a 7 year lifetime on the High Performance > option, the replacement Physics package was over $20,000 some years back. > So that's a cost of ownership of around =C2=A32,000 per year after layin= g out > the cost of a cheap house. Even if you go for the lower performance optio= n > involving a reduced beam current and poorer stability you still have the > initial cost and >=C2=A3600 per annum cost of replacing the Cs. > > The earlier 5061's that sometimes pop up surplus had around 5-6 year run > lives so could require a very expensive repair. So the Cs clocks in Ham > ownership are few and far between. An "unused " one is not a good idea > either, the physics pack needs to be in standby not off ! > > The notion that a Cs clock is primary is interesting. Although time is > now defined as a number of cycles of a Cs state transition frequency that > applies to very long tubes run as National Standards and given a National > Standards level of support, a rack mount short tube IS TWEAKED onto > frequency by adjusting the C magnet field. The tweak is very fine however > it is finite, the Cs resonance is quite wide- around 1KHz- and is biased = by > an axial magnetic field. Individual rack mount clocks do show some > variation, for critical applications people run groups of clocks and > average the outputs ( e.g. the working GPS master standard) > > It seems improbable that Cs will be "primary" much longer, H has better > short term noise whilst laser cooled clocks go way beyond the Cs limits b= y > greatly reducing thermal noise however they won't be cheap.The question o= f > which will win is complicated because the different systems keep > leapfrogging in performance as new refinements are developed. > > Rb and Cs clocks are atomic resonators, they work by amplitude locking th= e > synth harmonics of a good xtal oscillator to the resonance so the noise > performance of the clock is that of the crystal oscillator at around 1S > averaging time. You cannot increase the loop bandwidth much because of > modulation leakage and bode stability. So a very good GPS corrected cryst= al > osc is about as good as an atomic standard for some uses in ham radio in > terms of short term noise. > > Good GPS based oscillators use Rb or high grade double oven crystal > oscillators that run with long integrating times. They offer hams > tracability of frequency and very low noise for very little cost, a secon= d > hand Trimble Thunderbolt or a Rapco Rb cost =C2=A3100-300 and deliver a v= ery > clean signal. > > There is the very low cost route of GPS Rx and huf and puf stabilisation > of a simple temp controlled oscillator. For the very low cost this does > give some degree of frequency certainty within a few Hz. However counting > the oscillator using the 1pps as a gate produces much lower stability as > the crystal hunts around the mean fx. To get closer to the quality of the > GPS signal a high grade crystal oscillator and integrated phase > measurements are needed but that provides a reference ideal for LF and MF > signalling at very narrow bandwidths. > > 73's > Alan G8LCO > __._,_.___ > ------------------------------ > Posted by: g8lco10@yahoo.co.uk > ------------------------------ > Reply via web post > > =E2=80=A2 Reply to sender > > =E2=80=A2 Reply to group > > =E2=80=A2 Start a new topic > > =E2=80=A2 Messages in this topic > > (2) > Visit Your Group > > > - New Members > > 3 > > [image: Yahoo! Groups] > > =E2=80=A2 Privacy =E2=80=A2 > Unsubscribe > =E2= =80=A2 Terms > of Use > > . > > __,_._,___ > --089e010d867c891e4a0526760bd3 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
What is needed is a design for a homebrew 1 PPS PHASE L= OCKED source. =C2=A0 =C2=A0Both the Brooks Shera =C2=A0and VE2ZAZ desig= ns are frequency locked loops - although it could be argued that frequency = and phase are the same things, and it is the order of the PLL that is diffe= rent.=C2=A0 But whatever... =C2=A0they give noticeable errors short to medo= ium term

Commercially quite low cost GPSDOs, like one I = have from [what used to be] Connor Winfield give results that when averaged= over a few minutes are quite accpetable in terms of absolute accuracy, and= are in the sub-PPB region over shorter periods. =C2=A0 =C2=A0The paper on = my web site, =C2=A0URL given in a previous post, shows the CWin =C2=A0GPSDO= short term stability.

Those low end units =C2=A0u= se what would appear to be phase locking, and I see no reason why a simple = edge triggered phase detector at 1PPS, using high speed logic couldn't = be made to work.=C2=A0 Problems ion the past have centred round phase detec= tors being not very useful when asked to deal with difference in tens of ns= , but these days, one made using VHF logic or a gate array ought to be able= to manage. =C2=A0=C2=A0I don't think an XOR phase detector is feasible= , the filtering to get rid =C2=A0of the 2Hz residue, even at very long time= constants, would be too much. =C2=A0 =C2=A0Getting a real long time consta= nt could be a bit of a headache without going into DSP, but good quality no= n electrolytics are around for several uF, and if we're not worried by = size, several in || to say 50uFm with 20M resistors around CMOS opamps ough= t to be good enough - that's up to 20 minutes time constant and in the = realm of needing an OCXO as the 10MHz source.=C2=A0 Construction would need= care to avaoid leakage though. =C2=A0 =C2=A0My MSF reference way-back-when= used CR values of this sort of value, and it did mostly work. Phase change= s of RF due to =C2=A0proximity effects around he ferrite rod were its major= downfall.

=C2=A0 And all the rest is just basic d= ivision

On 9 December 2015 at 02:54, g8lco= 10@yahoo.co.uk [rsgb_lf_group] <rsgb_lf_group@yahoogroup= s.co.uk> wrote:
=20
=C2=A0
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It is a not insignificant fact that Caesium Clocks are very expens= ive and have finite lives as their caesium "fill" moves from the = source end to the ioniser. Current HP 5071's have a 7 year lifetime on = the High Performance option, the replacement Physics package was over $20,0= 00 some years back. So that's a cost of ownership of=C2=A0 around =C2= =A32,000 per year after laying out=C2=A0 the cost of a cheap house. Even if= you go for the lower performance option involving a reduced beam current a= nd poorer stability you still have the initial cost and >=C2=A3600 per a= nnum cost of replacing the Cs.

The earlier 5061's=C2=A0 that som= etimes pop up surplus had around 5-6 year run lives so could require a very= expensive repair. So the Cs clocks in Ham ownership are few and far betwee= n. An "unused " one is not a good idea either, the physics pack n= eeds to be in standby not off !

=C2=A0The notion that a Cs clock is = primary is interesting.=C2=A0 Although=C2=A0 time is now defined as a numbe= r of cycles of a Cs state transition frequency that applies to very long tu= bes run as National Standards and given a National Standards level of suppo= rt, a rack mount short tube IS TWEAKED onto frequency by adjusting the C ma= gnet field. The tweak is very fine however it is finite, the Cs resonance i= s quite wide- around 1KHz- and is biased by an axial magnetic field. Indivi= dual rack mount clocks do show some variation, for critical applications pe= ople run groups of clocks and average the outputs ( e.g. the working GPS ma= ster standard)

It seems improbable that Cs will be "primary&quo= t; much longer, H has better short term noise whilst laser cooled clocks go= way beyond the Cs limits by greatly reducing thermal noise however they wo= n't be cheap.The question of which will win is complicated because the = different systems keep leapfrogging in performance as new refinements are d= eveloped.

Rb and Cs clocks are atomic resonators, they work by ampli= tude locking the synth harmonics of a good xtal oscillator to the resonance= so the noise performance of the clock is that of the crystal oscillator at= around 1S averaging time.=C2=A0 You cannot=C2=A0 increase the loop bandwid= th much because of modulation leakage and bode stability. So a very good GP= S corrected crystal osc is about as good as an atomic standard for some use= s in ham radio in terms of short term noise.

Good GPS based oscillat= ors use Rb or high grade double oven crystal oscillators that run with long= integrating times. They offer hams tracability of frequency and very low n= oise for very little cost, a second hand Trimble Thunderbolt or a Rapco Rb = cost =C2=A3100-300 and deliver a very clean signal.

There is the ve= ry low cost route of GPS Rx and huf and puf stabilisation of a simple temp = controlled oscillator. For the very low cost this does give some degree of = frequency certainty within a few Hz. However counting the oscillator using = the 1pps as a gate produces much lower stability as the crystal hunts aroun= d the mean fx. To get closer to the quality of the GPS signal a high grade = crystal oscillator and integrated phase measurements are needed but that pr= ovides a reference ideal for LF and MF signalling at very narrow bandwidths= .

73's
Alan G8LCO

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__._,_.___
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Posted by: g8lco10@yahoo.co.uk
Reply via w= eb post =E2=80=A2 Reply to sender =E2=80=A2 Reply to group =E2=80=A2 Start= a new topic =E2=80=A2 Messages in this topic (2)
=20 =20
Visit Your Group
3D"Yahoo!
=E2=80=A2 Privacy =E2=80=A2 Unsubscribe =E2=80=A2 Terms of Use

=20 =20 =20 =20
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= =20
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