[time-nuts] Road-trip and rubidium fiddles

[Azelio Boriani]

Interesting, now two questions:

>It is clear that the short term is limited by the instrument trigger
jitter. A mixer pre->scaling is clearly needed.

that is, a mixing to take down the 10MHz to a lower frequency? Mixing with
a higher stability source?

And,
>I also gave a quick tour of just how much you can read out of the clock's
state and >status using the knob and voltmeter. Showing the locking in
process and such.
OK, my SR620 will arrive soon (it is actually in the Custom office to
compute the duties) but this tells me that the SR620 can measure with high
precision the incoming AC signal level? Why locking-in process? Has the
SR620 to lock-in the input signal source?

OK, maybe I have to study the SR620 manual first...

On Mon, Apr 9, 2012 at 4:03 PM, Magnus Danielson <magnus at rubidium.dyndns.org
> wrote:

> Fellow time-nuts,
>
> I spent Easter leave to go on a road-trip, taking me by fellow time-nuts
> Björn and Poul-Henning, and naturally lots of other good friends.
>
> On my way out I lent Björn one of my HP5065A and a SR620. On my way back I
> looked at his measurements. One of the things which was obvious was that he
> had a 1E-10/tau slope as he compared his 5065A against mine. Mine was
> slightly of frequency so he had adjusted that. Thanks. I think I had put it
> deliberately off at one point.
>
> Anyway, when using the 1 cycle jitter as a trigger jitter measure, mine as
> about 30 ps RMS jitter while his was about 100 ps RMS jitter.
>
> Scoping them both proved that mine had significantly higher amplitude, and
> both where nice sine signals when loaded with 50 Ohm.
>
> So, looking up the manual I traced the signal back to the C1 trimmer in
> the A3 module. Sadly enough they had not made an adjustment hole for C1 in
> the A3 shielding, so it was 22 screws just to get the shield off and 2
> screws to unscrew the A3 block. It didn't take much adjustment to get it up
> to the same level as mine, and naturally jitter went down.
>
> As a result, the readings came out as a 2E-11/tau slope. However, this is
> too low, and we then figured out that the Source setting was wrong,
> something I should have noticed but didn't (Björn was quick to point out
> that I should have known better, and well... I should but... I blame I was
> tired). So, after that we had a 3E-11/tau slope.
>
> It is clear that the short term is limited by the instrument trigger
> jitter. A mixer pre-scaling is clearly needed. It is expected.
>
> I also gave a quick tour of just how much you can read out of the clock's
> state and status using the knob and voltmeter. Showing the locking in
> process and such.
>
> All in all a few stumbling steps in the right direction in the sign
> tiredness.
>
> Cheers,
> Magnus
>
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>