Hi There always is a …. but ….
When you slow down the temperature change process, you increase the length of hanging bridges on the pps output. That might not be a big deal with NTP or in an application that uses the sawtooth correction message. In an application where a post filter process is expected to average out the sawtooth, it can be an issue. Bob > On Nov 4, 2017, at 6:16 AM, Leo Bodnar <[email protected]> wrote: > >> From: MLewis >> Is this coincidence or can reception improve with: >> - a higher temperature module? >> - a more stable module temperature? > > Short answer: > #2 > > Long answer: > Ublox firmware tracks gradual shifts in its reference frequency (XO, TCXO or > external input) and adjusts LO base offset to compensate. > > However, the time constant of this correction tracking loop is quite high > (and can be adjusted depending on the reference oscillator type.) > > Sudden changes in temperature and, as a result, in reference frequency result > in correlation level drop (seen as sat signal level level drop) or in total > loss of tracking and return to acquisition. > > In other words, absolute reference frequency offset (i.e. its temperature) is > not a problem - it is gradually compensated for, but sudden shifts in > frequency are. > > If your design does (hopefully) does not rely on convection for getting rid > of heat, try filling internal voids with cotton wool. This will stop > turbulent (naturally random) and laminar (usually caused by external events) > airflows from affecting the reference. Compartmentalising the design is just > another way of separating the airflows but it does not stop them within the > compartments. > > There are subtler cases where reference frequency source has a sweet spot > where its stability is greatest (like OCXO) and absolute temperature matters > as well but this is the first order effect. > > Leo > _______________________________________________ > 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.
