[time-nuts] Usefulness of high end counters for ADEV plots of oscillators

paul swed paulswedb at gmail.com
Sat Jan 31 09:53:14 EST 2015

Very interesting on the HP5360 and that it could do ADEV. I had no idea and
actually don't know how that would be done. I can appreciate the HP
Engineers distaste for the 5360. Its very complex to repair. I have 5 of
them with the keyboard and they work. The worlds biggest calculator by size
and weight. Very good oven in them.
Not to take over the thread, few ever heard of the 5360.
It seems the 53230 may be just a bit lighter.
OK now to go see if I can hunt down how you do adev.

On Fri, Jan 30, 2015 at 7:13 PM, Richard (Rick) Karlquist <
richard at karlquist.com> wrote:

> First of all, the oven oscillator option of the 53230
> is no where near as stable in ADEV as a 10811 for example.
> The counter itself is 1 or 2 orders of magnitude better
> than the built in timebase.  So don't waste your money
> on the OCXO option when you, as a time nut, undoubtably
> already own something like a 10811.
> When I was still with Agilent, I made innumerable measurements
> of ADEV with a 53230 down into the low parts in 10^11, which
> was the DUT ADEV, not limited by the counter.  I vaguely
> remember measuring a 10811 as a sanity check and using
> the internal OCXO (not knowing any better).  After wasting
> a lot of time, I eventually measured one 10811 against
> another and discovered that the ADEV floor was down to
> 1E-12 at least, and that the internal OCXO was junk.
> About the only good thing about the 53230 is that it
> is a self contained box that makes ADEV measurements and
> displays them in real time without requiring an external
> computer with software.  In 1974, HP made a computing
> counter (5360 I think) that did this.  Customers loved this
> box, but the HP engineers hated the box.  Therefore, no
> HP/Agilent counter ever did ADEV again, until the product
> line was offshored to engineers who didn't know any better
> and put the feature back in.
> For serious ADEV measurements, you want two DUT's offset by
> a few 100 Hz and mixed, as originated in the HP 5490 system.
> Rick Karlquist N6RK
> On 1/30/2015 8:38 AM, James via time-nuts wrote:
>>   Though I'm new to the list I've lurked for quite a while
>  and from reading various posts I am in a slightly confused
>  state as to whether buying an expensive counter (eg Keysight 53230A
>  or a Tek fca 3100) will be useful as a measurement tool for
>  developing a GPSDO.
>> Given a one shot measurement resolution of 50 psecs (on the Tek which is
>> a pendulum CNT91) means that the uncertainty is around 50E-12 at 1 sec or 5
>> x 10^-11 or 10^-10 in round numbers for a ADEV at 1 sec? For this noise
>> floor to get well below 10^-11 (the sort of ADEV of an OCXO) requires the
>> interval to be increased to nearer to 100 seconds?
>> So does this mean that an expensive counter allows useful ADEV plots from
>> 100 seconds on but not the lower time frames? (By useful I mean able to
>> measure down to and below 10^-11 not down to 10^-14!)
>> The extra cost of the 53230A over the 3100 gets down to 20 psecs so
>> possibly reduces the period to a bit less than 100 seconds but still above
>> 10 seconds probably?
>> Does paying extra for an OCXO gain significantly on this basis?
>> Have I got the basic numbers right, and if one of my main aims is to have
>> a good instrument for playing with GPSDO development will investing in such
>> an expensive (for an individual hobbyist) instrument buy me a useful
>> measurement capability or would it just be good for measuring long term
>> frequency and say 1pps jitter from the GPS?
>> Sorry for the long post,
>> James
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