Hi Erno Thanks for your suggestion; while it is convenient to have everything already planned out, I'm inclined on DIY'ing as much as I can :-)
Ray Xu On Sun, Jan 29, 2012 at 1:01 AM, Erno Peres <[email protected]> wrote: > > Hi Ray, > > please find on this link the info what you are looking for. > > http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm > > Rgds Ernie. > > > > > > > > > > -----Original Message----- > From: Ray Xu <[email protected]> > To: time-nuts <[email protected]> > Sent: Sun, Jan 29, 2012 7:51 am > Subject: [time-nuts] Building a GPSDO & trouble using Jupiter-T > > > Hi guys > I'm planning to build a GPSDO to use as a frequency ref for my GHz > ventures. > I've done research in what other people have built - but I have no > xperience working with long-term precision/stability products (nor do I > ave the equipment to do so -- I think). > I'm using the Jupiter T (the one with the 10-pin header) GPS and its 10KHz > utput in an analog PLL that controls a 10MHz VCXO. It would be ideal for > e that if I were to multiply the 10MHz output up to 10GHz, I would get > bout a few Hertz or so of inaccuracy. It would also be ideal if I can > ave a PLL lock time of a few minutes while maintaining accuracy. > However, right now as I am trying to design my project, I can't find enough > nformation on the web regarding the VCXO's (or the PLL oscillator, in this > ase) short term accuracy effect on output frequency. I know that its > hort term accuracy depends on the "response time" of the PLL, which also > epends on the amount of jitter from the Jupiter-T's 10KHz output... I > now that the longer the time constant for the PLL, the better accuracy, > ut I do not want to wait, literally, hours for it to lock... > Also, what is the advantage of using a OCXO instead of a VCXO in terms of > hort-term accuracy? If the PLL time constant is only a few seconds, then > crystal shouldn't deviate in frequency by too much within a few seconds, > ssuming I'm using a crystal bought from a well-known manufacturer...or > ould it? I am inclined towards using oscillators that do not require any > ignificant warm up time... > For those who have experience using the Jupiter T GPS: > have bought this > ttp:// > www.ebay.com/itm/Navman-jupiter-T-Tu60-GPS-Kit-1pps-10khz-GPS-Module-/260790984470but > could not get it to communicate via serial. So far, I do not have > n > ntenna available and so the antenna port is just left disconnected. When > turn it on, there is a 1pps and 10KHz signal and the TX line is at logic > igh. However, I cannot get it to communicate to anything else, even a > umb terminal. It does not respond to when I send a message ID to it. > Because of computer difficulties, I am using the PicKit 2's UART tool). > s my device a dud or am I doing something wrong? > Many inputs is highly appreciated. Thanks > -- > _________ > 3, Ray Xu > F5LJO > ______________________________________________ > ime-nuts mailing list -- [email protected] > o unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > nd 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. > -- __________ 73, Ray Xu KF5LJO _______________________________________________ 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.
