[time-nuts] ADEV query Timelab and TICC
John Ackermann N8UR
jra at febo.com
Mon Mar 20 12:16:53 EDT 2017
I noticed with the TICC that the very high peak voltage on the 5061, 5065, etc. PPS causes trigger errors. Putting a 50 ohm load at the TICC channel input helped a lot, or an attenuator might even be better.
These HP units have a very short pulse width that peaks at something like 20v into a high impedance. It doesn't seem to hurt the TICC input circuit, but causes ringing that results in perceived jitter. Knocking that down to TTL level solves the problem.
On Mar 20, 2017, 12:01 PM, at 12:01 PM, timeok <timeok at timeok.it> wrote:
>
> All,
>the similar problem I have verified using the HP5065A and HP5061B 1PPS
>output, the dividers are pratically unusable for ADEV measurements. The
>5/10MHz output of the same instruments using the TAPR divider are ok,
>so these dividers have some spike noise problems. It can be seen even
>using other TIC as The HP53132A.
> Luciano
> www.timeok.it
>
>
> Da "time-nuts" time-nuts-bounces at febo.com
>A "Discussion of precise time and frequency measurement"
>time-nuts at febo.com
> Cc
> Data Sun, 19 Mar 2017 20:03:29 -0700
> Oggetto Re: [time-nuts] ADEV query Timelab and TICC
>> I have sent a couple of files to Tom. They were taken simultaneously
>from
>> an LTE Lite - one from the PPS and one from a PicDiv dividing the
>10MHz to
>> 1Hz. The glitches were on the PPS trace, but not on the PicDiv trace,
>so
> > I'm fairly confident the TICC was working correctly.
> >
> > Orin.
>
> Hi Orin,
>
>Thanks for the raw data. It's very nice (2 hours 16 minutes = 8219
>points). Everything looks fine with the exception of 8 glitches. These
>are sometimes obvious jumps in phase, which cause massive spikes in
>frequency. Two plots attached.
>
>Almost every data point is within a few ns of each other. This is good.
>The standard deviation is a fraction of 1 ns. But once in a while there
>is a relatively massive phase jump. This is bad. Interestingly these 8
>phase jumps all appear to be about 25 ns or a multiple of 25 ns in
>magnitude. The full list is (ns units):
>
> 24.575
> 24.724
> 24.831
> 25.047
> 25.087
> 25.549
> 25.589
> 49.623
>
>25 * N ns is not random. So I think this is not a Windows problem, not
>a USB problem, not a TimeLab problem, not a TICC problem either.
>
>It makes me wonder if this is a LTE-Lite problem. If Said or Keith from
>Jackson Labs is around -- is there anything on the LTE-Lite board
>that's close to 20 or 40 or 80 MHz? At this point I kind of trust
>Orin's data and I kind of trust the TICC. So when I see monster 25 ns
>phase jumps it makes me think there's a problem with the GSPDO board
>itself.
>
>(Please realize that only on time-nuts may we can use the words
>"monster" and "25 ns" in the same sentence; the rest of the world has
>larger problems)
>
> /tvb
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