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.
