[time-nuts] CW12-TIM vs M12M and the world
Erno Peres
ernieperes at aol.com
Sat Mar 31 13:10:07 UTC 2012
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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