John The jitter of the Wenzel waveform conversion circuit will vary with the input signal amplitude. Thus one could probably measure the jitter as a function of input signal amplitude and derive the waveform conversion circuit jitter performance from that data.
Bruce John Ackermann N8UR wrote: > I can do that, but was hoping to isolate the performance of the Wenzel > waveform conversion circuit. An initial test showed jitter of about 25 > ps -- which is about the same as for the whole divider chain, so you may > be correct that the input amplifiers are limiting. But also, I was > doing a quick and dirty setup without paying much attention to how the > signal was coupled. I'll be able to improve on that in tomorrow's > experiments. > > John > ---- > > Bruce Griffiths said the following on 04/04/2009 05:37 PM: > >> John >> >> With a slow slew rate input signal like a 10MHz sinewave the Wavecrest >> jitter due to the noise of its wideband input amplifiers may be quite high. >> >> So it may be better to measure the relative jitter of 2 dividers. >> >> Bruce >> >> John Ackermann N8UR wrote: >> >>> Hi Brian -- >>> >>> It's good to collect this data; thanks. It's interesting that your std >>> dev in the first test seems to increase significantly with the number of >>> samples; I haven't seen that kind of scaling here (1K sample and 10k >>> sample turned in very similar std dev). From what Poul-Henning said >>> earlier, your first run may suffer the same distortion as my data at the >>> bottom of this thread. >>> >>> I just finished rerunning the TADD-2 test using a Wavecrest DTS-2075 >>> (the first real use I've had for that box!) and with 1 PPS input on the >>> start channel, 10 MHz from the same source on the stop channel, and 10K >>> samples, I got 22.0 ps of jitter, and a 92 ps min/max range. (As far as >>> I can determine, the Wavecrest doesn't allow you to use an external >>> reference, and its internal reference runs at 100 MHz so it probably >>> wouldn't be useful in this measurement.) >>> >>> That's consistent with what I measured earlier with the 5370B when I >>> didn't have the reference and the inputs in coherence. It appears that >>> the test below, where I used the same reference for *everything* >>> triggered the problem that Poul-Henning warned about, so those results >>> should be disregarded. >>> >>> While I haven't done any testing to validate this, I think the complaint >>> about the 74HC390 dividers isn't so much their jitter in normal use, but >>> the tempco problems the cascaded stages can cause. If you can do it, it >>> would be interesting to measure the phase change over temperature -- >>> I've done a preliminary experiment on that for the TADD-2, but plan to >>> rerun it with much better measurement technique. >>> >>> I'm also hoping to do a jitter and tempco test of the Wenzel input >>> conditioning circuit by itself. I really like that circuit for its wide >>> input amplitude range. >>> >>> John >>> ---- >>> Brian Kirby said the following on 04/04/2009 04:18 PM: >>> >>> >>>> I will report some results on a asynchronous divider, which I basically >>>> copied from Dr. Thomas Clark's designs, which everybody likes to report >>>> as a bad design. >>>> >>>> The 10 MHz input signal is coupled thru a resistor and capacitor. On >>>> the other side of the capacitor is the resistive divider that is tied to >>>> Vcc and ground - it biases the signal to 2.5 volts, which is feed to the >>>> input of the 74HC132. The output of the 74HC132 feeds several 74HC390s >>>> until it becomes a buffered 1 pulse per second signal. I also have >>>> buffered 5 MHz and 1 MHz outputs. The other 3/4 of the 74HC132 are used >>>> to externally synchronize the 74HC390s. >>>> >>>> I used the Thunderbolt as the source of 10 MHz and it was feed to the >>>> divider, and the stop input on the HP5370B. The 5370B was run on >>>> internal clock. The 1 PPS from the divider feed the start input on the >>>> 5370B. >>>> >>>> 100 seconds TI 79.865 nS MIN 79.80 nS MAX 79.98 nS STD 36.4 pS. >>>> 1000 seconds TI 79.831 nS MIN 79.71 nS MAX 80.00 nS STD 49.9 pS >>>> 10K seconds TI 80.1552 nS MIN 79.79 nS MAX 80.88 nS STD 271 pS >>>> 100K planned >>>> >>>> Also a second test, using the Thunderbolt as a source of 10 MHz and it >>>> was feed to the divider, the stop input on the 5370B and the external >>>> clock of the 5370B. The 1 PPS from the divider feed the start input on >>>> the 5370B. >>>> >>>> 100 seconds TI 75.002 nS MIN 74.96 nS MAX 75.04 nS STD 22.5 pS >>>> 1000 seconds TI 74.931 nS MIN 74.80 nS MAX 75.04 nS STD 56.8 pS >>>> 10K seconds TI 77.5135 nS MIN 77.40 nS MAX 77.62 nS STD 35.9 pS >>>> 100K measurement in progress. >>>> >>>> I believe having STD in parts of 10-14th is fairly respectable for >>>> amateur designs.. >>>> >>>> Brian KD4FM >>>> >>>> John Ackermann N8UR wrote: >>>> >>>> >>>>> I just finished a jitter test of the first TADD-2 built on the >>>>> production circuit board. >>>>> >>>>> The configuration was somewhat optimized from what I used for the >>>>> earlier tests. >>>>> >>>>> A single 10 MHz source was daisy-chained to the TADD-2 input, to the >>>>> 5370B external reference input, and to the 5370B STOP channel. The 1 >>>>> PPS output from the TADD-2 was connected to the 5370B START channel. >>>>> Thus any reference jitter shouldn't be common-mode, and using the >>>>> reference clock on the STOP channel avoids the need for a second >>>>> divider, and ensures that the time interval is small (always less than >>>>> 100 ns; in this case, about 90 ns). >>>>> >>>>> For a 10,000 sample run, the standard deviation was 12.1 picoseconds, >>>>> and the peak-to-peak variation was 70 picoseconds. Based on experiments >>>>> I ran a few years ago, I think this is pretty much the noise floor of >>>>> the 5370B and the divider could be better than this. >>>>> >>>>> John >>>>> >>>>> _______________________________________________ >>>>> 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. >>>> >>>> >>> _______________________________________________ >>> 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. >> > > _______________________________________________ > 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.
