These times are 400ns apart which corresponds to the duration of the assembly instructions running at 10MHz (or 800ns which corresponsd to the duration at 5MHz) on a PIC microcontroller. TVB has a blurb about this somewhere in his PPSDIV assembly code which the TADD-2 is based on.
http://www.leapsecond.com/tools/PPSDIV.ASM -Bob, N3XKB On Wed, Sep 16, 2009 at 3:48 PM, Brian Kirby <[email protected]>wrote: > I have built two TADD-2's and have been using them in the timing shop. I > noticed a synchronization problem and I wanted to pass it on and see if > anybody else seen the same problems. > > What I noticed is the units seem to want to sync within three discreet > values of time ; of the source. I have to press the sync button and watch > the output to confirm where its set. I have to press the sync button > several times to get the proper value. Attached is a drawing of the test > setup. > > The data is for two TADD-2 units, I will call them units A & B. > > Using 10 Mhz input , unit A will either sync to 171 nS, 571 ns or 971 ns. > Unit B will sync to 71 nS, 471 nS or 871 ns. > > Using 5 Mhz input, unit A will sync 400 ns, 1.200 uS or 2.000 uS. Unit B > will sync to 600 nS, 1.400 uS or 2.200 uS. > > The Austron 1210 shows 3.5 volts P-P terminated sine waves on the scope for > 10 and 5 Mhz, the 1 PPS is +5.8 volts peak, also terminated. > > Both TADD-2 were acquired and built less than a month ago - so the parts > should be identical values. The only difference is power supply. Unit A > runs off my 12 volt system that powers my GPS receivers. Unit B has a 9 > volt DC wall wart rated at 0.5A. > > I changed the RF Input to my HP5065A and I still see three different values > of time; Unit A -102 nS, 698 nS, and 1498 nS. Unit B shows 502 nS, 1302 nS > and 2102 nS. > > I change to other RF and PPS sources and I see the same problem. > > My concern is this is repeatable, in my case, and I have to watch the > output to get the sync as close to the source, timing wise with the TADD-2. > My other dividers, based on async logic do not show this problem. One > unit syncs solid at 160 nS on 10 Mhz, the other unit at 210 nS (they were > built several years apart and probably different brands of gates). > > Brian - KD4FM > > > > > > > > > > _______________________________________________ > 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.
