Being divorced and no children writing a large check is neither a problem nor a challenge. To me the challenge is to find solutions that are affordable and work for every body. Sadly there is very little interest or emphasis in this group on this. An example the $ 10 Loran C simulator that Paul and I build and tested, turning obsolete Loran C Receivers in to high resolution frequency displays. Many other projects off list. The way I understand it the discussion on GPS receivers, in this thread started looking for a solution for the FE 5680A. To look at the proper configuration, first there has to be a good understanding of the Rb. Aging will determine the update rate of the Rb. Second the choice has to be made if digital or analog frequency control will be implemented. Digital dither or no dither. With out dither we are talking 3 E-13 setability. Enough? Some one has to test how the Rb reacts to dither. Right now I se a 4 to 5 Hz control loop in my tests. Analog 1 E -14 is no problem. With aging and step requirement a loop can be defined. Being Rb, it can be a long loop which will reduce requirements of the GPS receiver and most likely issues like ionospheric delays will play a roll. That is the time to ask the question what does the GPS receiver have to be. All the other chatter should be part of a different thread because it may confuse some of the readers. How many FPGA's are running and can be copied by members? Many have bought FE 5680 A and have no idea how their individual unit performs. I have seen 8 E-10 off frequency. Bert Kehren In a message dated 2/1/2012 2:47:51 P.M. Eastern Standard Time, t...@leapsecond.com writes:
Chris, When you're down at the ns level, every ns counts even more. There actually a "huge" difference between a UT and VP and M12 and ... Then again, it's not always about nanoseconds. There are also issues of power and size, support, supply, price, the future. Perhaps also RF sensitivity, feature set, upgrade path for the likes of GLONASS or Galileo, acquisition time. Even RoHS. Perhaps this doesn't matter for a one-off hobbyist, but if you're making kits or products it can become an important factor. If you are inclined to experiment, just for the sake of exploring as many of us on the list are, then certainly you'd want to get a u-blox at some point. It doesn't have to be right away, but it is a pretty nice, very modern, ultra compact, timing receiver. If low cost is the object it's hard to beat that MG1613S board. /tvb > What is it these u-blox device can do that a cheaper Motorola Oncore > can't? Depending on the version the Oncore has for 50 to 5 nS > one-sigma error on the timing pulses and can do either 1PPS or 100PPS. > Single unit prices are from $18 to $60 very good documentation is > available. > > If the u-blox was somehow much better than a Trimble thunderbolt or > Motorola Oncore MT12T I'd buy one even at the above price. But > really these older GPSs are already at the single digtit of > nanoseconds level and I don't see room for improvement except.... > > If the L2 band is also used. This is the way to get order of > magnitude improments > > > Chris Albertson > Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/ma ilman/listinfo/time-nuts and follow the instructions there. _______________________________________________ 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.