[time-nuts] CW12-TIM vs M12M and the world

Sat Mar 31 13:25:34 UTC 2012

OK, I'll study the PRS10 manual.

On Sat, Mar 31, 2012 at 3:10 PM, Erno Peres <ernieperes at aol.com> wrote:

>
> Hi Ulbrich,
>
> Sorry but not everybody a digital and/or a  professional guru... can you
> please be a more specific.... namely to show us the pre filter and other
> circuit....if you do not mind.
> Understand that the key point is the PLL or the phase comparator
> circuit.........if you want to build you own GPS-DO.....
>
> Many thanks and best regards,
>
> Ernie.
>
>
>
>
> -----Original Message-----
> From: Ulrich Bangert <df6jb at ulrich-bangert.de>
> To: 'Discussion of precise time and frequency measurement' <
> time-nuts at febo.com>
> Sent: Sat, Mar 31, 2012 2:53 pm
> Subject: Re: [time-nuts] CW12-TIM vs M12M and the world
>
>
> Bert,
> sometimes a manual can be a true treasure chest! Just download the PRS-10
> anual at
> http://www.thinksrs.com/downloads/PDFs/Manuals/PRS10m.pdf
> and find starting on page 13 the complete instructions on how to build your
> wn GPSDO. A basic knowledge of math, programming and control theory is
> eeded to understand the manual but then: It works. I have constructed my
> own DIY GPSDO on the base of the information that I have found there,
> ncluding the pre-filter.
> Best regards
> lrich
> > -----Ursprungliche Nachricht-----
>  Von: time-nuts-bounces at febo.com
>  [mailto:time-nuts-bounces at febo.com] Im Auftrag von EWKehren at aol.com
>  Gesendet: Samstag, 31. Marz 2012 13:46
>  An: time-nuts at febo.com
>  Betreff: Re: [time-nuts] CW12-TIM vs M12M and the world
>
>
>  Ulrich
>  can you tell us more about your pre filter?
>  Thank you
>  Bert Kehren
>
>
>  In a message dated 3/31/2012 6:23:49 A.M. Eastern Daylight Time,
>  df6jb at ulrich-bangert.de writes:
>
>  Thomas,
>
>  > Has anyone compared the M12M to the  M12+?
>
>  I have done some measurements on the M12+ with typical
>  results as  shown in
>
>  http://www.ulrich-bangert.de/M12Performance.jpg
>
>  The red  line is the raw phase data of the M12's PPS against
>  a PPS derived from a  local FRK-L rubidium. Note that you do
>  not observe an overall difference  frequency (and a resulting
>  drift in phase) because the FRK-L is disciplined  by the GPS.
>  The blue line is the sawtooth corrected phase data and it
>  becomes immediatly clear HOW IMPORTANT applying the
>  correction is. The  yellow line show you what happens if the
>  sawtooth corrected phase data is  sent through a pre-filter
>  (lowpass with 1/3 the time constant of the
>  main
>  pll loop) before entering the loop itself. That is something
>  that I  learned from the PRS-10 manual. You may decide on
>  your own which data you  would
>  like
>  to work on in a GPSDO.
>
>  Best regards
>  Ulrich Bangert
>
>  > -----Ursprungliche Nachricht-----
>  > Von:  time-nuts-bounces at febo.com
>  > [mailto:time-nuts-bounces at febo.com] Im  Auftrag von Tom Knox
>  > Gesendet: Freitag, 30. Marz 2012 22:19
>  >  An: Time-Nuts
>  > Betreff: Re: [time-nuts] CW12-TIM vs M12M and the  world
>  >
>  >
>  >
>  > Has anyone compared the M12M to the  M12+?
>  > Thanks for all the input, it is really appreciated.
>  > best  wishes;
>  > Thomas Knox
>  >
>  >
>  >
>  > > CC:  time-nuts at febo.com
>  > > From: saidjack at aol.com
>  > > Date: Fri,  30 Mar 2012 09:53:17 -0700
>  > > To: time-nuts at febo.com
>  > >  Subject: Re: [time-nuts] CW12-TIM vs M12M and the world
>  > >
>  >  > Hello Ed, Azelio,
>  > >
>  > > We should also compare the  same parameters. Sawtooth error
>  > of the m12+
>  > > of +/-25ns  is not its standard deviation, it's max/min.
>  > Compare that
>  >  > number to your 30ns max/min measurement on the 5372a.
>  > >
>  > > Standard deviation of the m12+ is around 2ns with
>  correction.  That
>  > > needs to be compared to the 5ns you measure on the 5372a
>  as  that is
>  > > the best performance you will get from the CW12. Yes the
>  > uncorrected
>  > > 1pps of the m12 is worse, but it is  designed to be used with
>  > > correction. So in the end the m12m  still performs better
>  than the
>  > > CW12.
>  > >
>  > >  Bye,
>  > > Said
>  > >
>  > > Sent From iPhone
>  >  >
>  > > On Mar 29, 2012, at 1:56, Azelio Boriani
>  <azelio.boriani at screen.it>
>  > > wrote:
>  > >
>  >  > > We (that is my company) use the CW12-TIM (NMEA version)
>  > and  its PPS
>  > > > wonders as usual, nothing different from a uBlox  LEA-5T
>  > or the M12M.
>  > > >
>  > > > On Thu, Mar  29, 2012 at 9:32 AM, Hal Murray
>  > > >  <hmurray at megapathdsl.net> wrote:
>  > > >
>  > >  >>
>  > > >>>> The sawtooth error on the Motorola  M12+ is about +/-
>  > 25ns, while
>  > > >>>> the  CW12-TIM has a sawtooth error of +/- 2 ns, so
>  > correcting for
>  >  > >>>> the sawtooth error is not as critical with the  CW12-TIM.
>  > > >>
>  > > >>> The first  claim
>  > > >>>> The sawtooth error on the Motorola M12+ is  about +/- 25ns
>  > > >>> is correct but are you absolutely  sure that the
>  second claim is
>  > > >>> correct  too?????
>  > > >>
>  > > >>> It would mean a  factor >10 improvement of the CW12-TIM
>  > against the
>  > >  >>> M12
>  > > >> which
>  > > >>> is  hardly believeable.
>  > > >>
>  > > >> The 25 ns  probably comes from period of the the free
>  > running clock
>  >  > >> they are using.  It doesn't seem unreasonable to me
>  to get  10x
>  > > >> better if they use a GPSDO for the local clock so  they
>  > can get the
>  > > >> PPS edge right where they  want it.
>  > > >>
>  > > >>
>  > > >>
>  > > >> --
>  > > >> These are my opinions, not  necessarily my employer's.  I
>  > hate spam.
>  > > >>
>  > > >>
>  > > >>
>  > > >>
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