Hi, On 08/18/2018 10:01 PM, Bob kb8tq wrote: > Hi > > > >> On Aug 18, 2018, at 2:25 PM, Attila Kinali <[email protected]> wrote: >> >> On Thu, 16 Aug 2018 17:45:30 +0200 >> Nicolas Braud-Santoni <[email protected]> wrote: >> >>> The main issue I'm running into is that most timing GPS modules will >>> happily give you carrier phase measurements... for their internal >>> oscillator, and the few ICs I can find that would possibly do the job, like >>> ublox's UBX-M8030-KT-FT, do not have publicly-available datasheets & docs. >>> (I tried contacting ublox to ask, and never got an answer...) >> >> Yeah. u-blox isn't as nice as they used to be to small customers :-( >> There are two ways to proceede: >> >> 1) use the timing of the PPS to deduce what the phase relation between >> your clock and the internal oscillator of the LEA is. >> In principle, this is possible, but I have not worked out the math, >> so I cannot say for sure. >> >> 2) replace the internal oscillator with one phase locked to your OCXO. >> The internal clock of the LEA is derived from a single TCXO. You can >> easily unsolder it and feed your own signal in. It should be relatively >> easy to reverse engineer what you need. If you don't want to reverse >> engineer it and if you get hold of a u-blox representative, you can get >> the required information from them. I got the data from them a couple >> of years ago. Unfortunately, I was explicitly asked not to share this >> information :-( > > If you go this route, the close in phase noise of your signal needs to be in > the > “pretty good TCXO” range. There are indeed some sources out there that > are way to noisy ….
Indeed. You want both pretty good wideband noise and close-in. Nowdays GPS-receiver TCXOs is their own class of TCXOs for a reason, and it's pretty impressive stuff for their size and cost. It's always good to keep an external ref input available to servo up the TCXO from. Cheers, Magnus _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
