[time-nuts] Re: Re: Newbie with questions (Alan Dev)
lymex at vip.sina.com
lymex at vip.sina.com
Fri Aug 5 08:36:33 EDT 2005
Thanks very much for all the responses for my questions, really helped.
Sorry for my late reply because I've off for last weekend and got busy at work.
Brian Kirby kirbybq at bellsouth.net wrote:
>As a quick reference of my 53131A, the noise floor at 1 second is
>1.7x10-10, 3 seconds is 4.0x10-11, for 6 seconds is 1.4x10-11, 10
>seconds is 4.8x10-12, 30 seconds is 1.3x10-12, 60 seconds is 7.4x10-13.
>This test is still in progress, so I do not have data for higher
Very nice. did you measure them by the internal Standard deviation function?
>I believe this is something we should all do, to get to know our
>instruments. Its a way to validate the data, considering that most of
>us do not have our test equipment in a calibration program.
Very much agreed.
Tom Van Baak tvb at leapsecond.com wrote:
>> I tried this method several time before by feeding the A
>> and B input the same 10MHz source, and the result is not
>> as good as promised.
>I suspect this jumping will occur when the two
>channels are highly synchronous; in this case
>some of the advantage of white noise averaging
>is not present. What you're seeing looks like
>LSB quantization effects to me. I would further
>guess the results would be different for slightly
>different lengths of cable between A and B.
Yes. Long cable gives large reading.
>The 53132A also has effects like this; there's
>a small footnote in the manual that mentions
>that resolution is reduced for certain bands
>of input frequencies. The normal 12 d/s drops
>down to 11 d/s.
Yes, the 53131A's manual is the same, although I'm not quite understand this part.
>Lastly, you might want to run the SR620 autocal.
>It may have no effect on your artificial test above
>but it should improve the stddev of the actual
>oscillator comparison tests.
Good, I've autocal the SR620, the reading is slightly better.
>Do you have RS-232 or GPIB capability on your PC?
That's the most painful part for me.
I have two notebook PCs and all have RS-232 ports.
But I don't have GPIB card.
I used to programming a lot but maybe difficult for me
to write code for access frequency counters now.
I'll either download or buy software for them.
I have HP34401A 6.5 digits multimeter and downloaded the
similar excel macro and it works!
I've downloaded the Agilent IntuiLink (version 1.2) at here
which is very similar but cannot get it running even by using
the same cable.
I am still looking a utility which can read from my SR620.
>Let us know the new results if you re-run the
>tests of your 6 frequency standards using this
>higher resolution frequency averaging mode.
I did more cross tests on some of the my frequency sources.
However, perhaps because I didn't setup the GPS antenna for Z3801A,
The output is bad. So I did not test the 2nd of my Z3801A.
Every raw data and the calculation is now here:
The results is not consistent although I re-measure some. The
reason I can think of is because the number of samples is small.
Anyway, The Trimble Thunderbolt (when holdover) has the lowest
(<4E-12) ADEV at TAU=1second.
>> Here is the example of my calculation:
>> Any comments or corrections?
>In the Excel page, I didn't understand method 1;
>it looked like first differences to me not second
>differences. Method 2 is correct. I verified your
>4.68e-12 ADEV result using Stable32. See
Ok and great. I'll use Method 2 from now on.
>One more thing; your phase data shows extremely
>high frequency drift, a rate of 1.4e-7 / day. This is
>odd. See phase and frequency plots:
Yes, this is perhaps due to the time I disconnect the antenna
is not very good. For the later measurement, I forced the
Trible Thunderbolt to holdover by the program.
Lymex Zhang / bg2vo
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