In article <[email protected]>, [email protected] says... > > David Lord wrote: > > > > Hi > > > > Latest experiment is to attempt to make a backup PPS source and > > I've now made a start with a watch xtal oscillator and divider > > that can be synchronised by a PPS source when present (except > > I've not yet wired up for synchronisation). > > > > remote refid st t when poll reach delay offset > > jitter > > ============================================================================== > > > > > > +GPS_NMEA(0) .GPSb. 0 l 57 64 377 0.000 1.865 > > 0.381 > > oPPS(0) .PPSb. 1 l - 16 377 0.000 -0.004 > > 0.002 > > PPS(2) .OSCc. 1 l 10 16 377 0.000 1.859 > > 0.006 > > -k6x400.home.lor 192.168.59.64 2 u 3 64 377 0.951 3.837 > > 0.447 > > +me6000g.home.lo .MSFa. 1 u 29 64 377 0.905 3.190 > > 0.451 > > -p4x2400c.home.l 192.168.59.64 2 u 34 64 377 0.832 3.078 > > 0.343 > > > > PPS(2) was time1 fudged to get it < 2ms. > > > > I can see there being problems already with full rotation of trim > > cap giving about +/- 6 us/s variation and temperature changes > > have already shown a minor problem (south facing window, very hot > > day, rapidly going cold tonight). Of course putting the whole > > oscillator module in a temperature controlled box is in the plan. > > > > Earlier this afternoon I had trimmer set so that offset change > > between poll periods was < +1us, but that started increasing and > > change has now reversed direction with offset over last hour > > having dropped from 1867us, steps at 6min intervals being: > > -31 -43 -54 -61 -59 -60 -58 -60 -59 -68 -75 -76us > > ie total 0.63ms over last hour. > > peerstats for yesterday: > ident cnt mean rms max > 127.127.22.0 5237 -0.003 0.039 0.217 GPSb pps > 127.127.22.2 5236 -10.938 4.678 11.263 OSCc pps > > I guess temperature variation over period has been < 15C > to > 25C. >
Take care, varicap diodes have significant tempco's too, and pot's can become very noisy after a while, even if you don't physicaly mess with them! We have lots of trouble with multi turn presets that set High Voltage PSU levels here at the salt mine. Seems a common thing, as I remember similar things when I worked at Tek UK years (cough... decades) back. Regards. Dave B(G8KBV) _______________________________________________ questions mailing list [email protected] http://lists.ntp.org/listinfo/questions
