On Wed, Aug 22, 2012 at 7:47 AM, Michael Tharp <g...@partiallystapled.com>wrote:
> > The design I'm thinking of is to have a separate microcontroller clocked > by the Rb that will generate a third pulse-per-second It is very hard to write a divers in software. You have to use assembly language and you have to mmake sure that EVERY path in every branch is has exactly the same number of clock cycles. And then you have to be lucky that you can work out an exact integer division. The above has been done but always the uP can't do anything else but the divide down loop. If you need some other background task use a second uP chip. I think a better way to do holdover is to use a stable OCXO that is phas locked to some timing source and then, in real time you might switch to the "best" source. If one of your source is a 10MHz Rb then why divide that down to 1Hz? Use the 10Mhz output to drive the OCXO. I can't draw a diagram so I'l use even more words... The "final" OCXO has 10Mhz output and is controlled by a PLL. The PPL has two 10Mhz inputs (references) it can choose from (1) the Rb and (2) a 10Mhz GPSDO. I think you need a uP to control the switch and also likely to manage the loop constants inside the PLL. I've been thinging about the because I have a few GPSes and an Rb also. That said this is not a high priority because in all the time I've been doing this I've not once seen a need for holdover. GPS seems to be 100% reliable. What I really want is a portable standard. So rather then the above I'mthinking about a GPS disiplined Rb. Then I can unplug the GPS and take the Rb where it is needed. Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.