[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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