[time-nuts] Short term 10MHz source

[Tom Van Baak]

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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