[time-nuts] Short term 10MHz source

[John Ackermann N8UR]

You've mentioned this before, and I'm having trouble getting my head 
around it.  I may have this all wrong, but isn't the quantization simply 
the resolution of the device?  Your histogram shows humps about 50 
picoseconds apart, but that's the resolution of the counter.

Wouldn't any counter that has 50 picosecond resolution look the same? 
Its data output is quantized by its resolution.  For example, the 5334A 
with 2ns resolution will always show bins no less than 2ns apart.

What am I missing?

John
----

On 1/8/19 3:34 PM, Tom Van Baak wrote:
> John,
> 
> Your hunch is correct. For most modern TIC devices, measurement noise is white. That is, if you do a self-test using a common DUT & REF you get a nice clean Gaussian plot. But the TICC is not like that. The TICC is based on a ring counter and so there is a *high* degree of quantization. This is not bad, per se, but it does impact how one should perform, or interpret, a noise floor test.
> 
> Take a look at: http://leapsecond.com/pages/ticc/
> 
> And in particular: http://leapsecond.com/pages/ticc/ticc-log5342-hist-1.gif
> 
> What this means is that a noise floor measurement made with the same chA and chB and REF could be quite wrong. This is not an indictment against the TICC. I have several, and use them all. But because of the strong quantization effects you can't just feed in a common DUT and REF and expect that to represent all possible real-life phase measurements. Those quantized "camel humps" are really quite extreme with the TICC.
> 
> /tvb
> 
> ----- Original Message -----
> From: "John Ackermann N8UR" <jra at febo.com>
> To: <time-nuts at lists.febo.com>
> Sent: Tuesday, January 08, 2019 10:48 AM
> Subject: Re: [time-nuts] Short term 10MHz source
> 
> 
>> Hi Luciano --
>>
>> Thanks for posting that.  There's a subtle point about the noise floor
>> that's forever been on my list of things to investigate: the noise floor
>> should be lower in timestamp mode than in time interval (A->B) mode.
>>
>> That's because in timestamp mode there is jitter contribution only from
>> a single measurement, whereas in time interval mode there is a
>> measurement from each channel so you have two jitter components.  So a
>> guess is that the floor should be about sqrt(2) lower in timestamp mode.
>>   Someday I will test that theory.
>>
>> John
>> ----
>> On 1/8/19 12:38 PM, timeok at timeok.it wrote:
>>>
>>>      .gif of the TICC noise floor.
>>>      Luciano
>>>
>>>
>>>      Da "time-nuts" time-nuts-bounces at lists.febo.com
>>>      A time-nuts at lists.febo.com
>>>      Cc
>>>      Data Tue, 8 Jan 2019 18:31:02 +0100
>>>      Oggetto Re: [time-nuts] Short term 10MHz source
>>>
>>>      Hi Paul,
>>>      here the TICC noise floor.
>>>      Regarding the GPS/TICC versus a good Rubidium standard like the HP5065A , you cannot apreciate the Rubidium ADEV stability lower than 10Kseconds.
>>>      Luciano
>>>
>>>
>>>      Da "time-nuts" time-nuts-bounces at lists.febo.com
>>>      A "Discussion of precise time and frequency measurement" time-nuts at lists.febo.com
>>>      Cc
>>>      Data Sat, 5 Jan 2019 12:35:26 -0000
>>>      Oggetto Re: [time-nuts] Short term 10MHz source
>>>      Hi All sorry for a new be question but what is a TICC regards Paul B UK
>>>
>>>      -----Original Message-----
>>>      From: time-nuts [mailto:time-nuts-bounces at lists.febo.com] On Behalf Of Chris
>>>      Burford
>>>      Sent: 02 January 2019 03:56
>>>      To: Time Nuts List
>>>      Subject: [time-nuts] Short term 10MHz source
>>>
>>>      I have a situation in which I have access to a GPSDO 10MHz source but for
>>>      only about 10-12 hours at a time. My current residence does not allow a
>>>      permanent GPS antenna therefore I am limited in its use.
>>>
>>>      I do realise that the long term stability of the GPSDO is somewhat superior
>>>      to a Rubidium source. I'm planning on using my TICC to validate both my
>>>      GPSDO and RFS. I'm aware that such a short "power on" period is somewhat
>>>      counterproductive but I have no other options. I'd like to know if a 6-8
>>>      hour window for the GPSDO is sufficient for use as a 10MHz source for the
>>>      TICC.
>>>
>>>      I appreciate any and all comments.
>>>
>>>      Regards, Chris
> 
> 
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