Attila I am pretty sure Anton is saying compare it to the H Maser and it simply doesn't in any way. I think we are speaking 1X10-11 compared to 1 X10-14th or so. Thats why I say forget all of the GPS stuff and go for an output from the maser to home. Now that would be a really fun project. Thinking RF. But need to stop going down that rabbit hole as I am lacking a good H maser. Sorry for the detour back to Antons thread. Regards Paul WB8TSL
On Wed, Jan 27, 2016 at 4:26 PM, Attila Kinali <[email protected]> wrote: > On Wed, 27 Jan 2016 12:17:32 +0000 (UTC) > Anton Moehammad via time-nuts <[email protected]> wrote: > > > Hi All, > > My GPSDO based from VE2ZAZ design but I have a few question I do > > not clearly understand about GPSDO, like : > > > 1.How important the quality of 1 PPS signal based from jitter etc what > the > > difference I will get between timing purpose GPS module like Ublox 6T or > > trimble resolution T with a position GPS module like ublox 6M or other in > > term of stability, accuracy and phase noise. > > I think the best improvement you can make is by not using a VE2ZAZ style > GPSDO :-) The design uses an FLL, which results in a slight frequency > error. If you change it to a PLL, you will only get a slight phase error. > > Next, PPS resolution will be limted by the uC internal counter. > Ie your resolution is in the 10-50ns range. You will need to get this > down to <1ns and apply saw-tooth correction if you want to see any > difference between a standard GPS receiver or a timing GPS receiver. > > As there is no LEA-6M I assume you mean the LEA-M8T. The Trimble > Resolution, > the LEA-6T and the LEA-M8T are all timing receivers. The differences > between > those are small. Smaller than all the other error contributions due to your > device design and your antenna position. Hence I wouldn't change the > receiver, once you have found one that fits your need. > > > 2. I understand short time stability from OCXO is better than GPSDO ? > > can someone give me a clue what the time constant need for OCXO control > > (in my application 30 second) is that enough ? > > This highly depends on your OCXO, your GPSDO design and the performance > the GPS receiver delivers. There have been many papers written on this > topic and you need a fair bit of understanding on control theory to apply > them correctly. Usual time constants for the control loop are between > one second and a couple of minutes. > > > 3. I have few Rubidium oscillator and I read somewhere (I believe in > KE5FX > > web) that GPSDO with rubidium osc is hard to beat, in what way ? short > time, > > long time, phase noise. > > The reason is because you can integrate over days using an Rb local > oscillator instead of just seconds or minutes. This filters out all > periodic perturbations induced by the GPS system. > The phase noise might or might not be better though. This highly depends > on how much care was given to the Rb's quartz oscillator output. > E.g. the ubiquitus FE-5680A has a very noisy output, worse than > a simple crystal oscillator. > > > > My goal is "simple" I have access to national time reference lab > > ( an active Maser H ) I want to compare my reference to them off course > > there is no way I have same stability but anything not so "embrace" is > fine > > to me > > I am not sure I understand what you mean here. Do you want to compare > your GPSDO to their H-maser? Or do you want to compare some local > reference you have using the GPSDO as transfer standard? > > > Attila Kinali > > > -- > Reading can seriously damage your ignorance. > -- unknown > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
