Hi The noise performance of the HMC1031 close in is pretty horrible. It’s actually *worse* than the GPS signal noise. In a normal GPSDO the idea is to use an oscillator that is cleaner at 0.01 to 10 Hz than the GPS.
Bob > On Sep 12, 2016, at 2:41 PM, Nick Sayer via time-nuts <[email protected]> > wrote: > > I was talking with someone at AD about a question I had about one of their > TinyDACs when they mentioned their HMC1031 chip. It looks like the ideal > building block for a clean-up oscillator. > > It struck me just a touch later that the Venus838LPx-T has by default a 10 > MHz output that’s phase locked to GPS time. It’s not good quality, but I > wonder if it’s good enough to be the reference for this particular chip. They > do talk about the ability to be driven by a “noisy” or "jittery” reference. > > I think I’m going to take a crack at an OH300 GPSDO based on this design > concept. Actually, first I’m going to actually try to quantify the jitter on > the 10 MHz output from the Venus. From the HMC1031 datasheet it appears that > if it’s not confined to a ±3 ns corridor that the lock indicator may not work > (or work well). That would be a bummer. > > I can foresee a GPSDO with the miniDIN 4 jack presenting the PPS and serial > I/O from the GPS module and two LEDs on the front - the “FIX” LED from the > GPS module and the lock LED from the PLL along with two BNC jacks. It would > have some downsides. For one, I believe in the absence of GPS reception, it > wouldn’t be able to properly hold-over at all. But it’ll be interesting to > see if it can work as well as the micro-controller driven variant does. > _______________________________________________ > 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.
