[time-nuts] Road-trip and rubidium fiddles

[Magnus Danielson]

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