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" <[email protected]>
To: <[email protected]>
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, [email protected] wrote:
.gif of the TICC noise floor.
Luciano
Da "time-nuts" [email protected]
A [email protected]
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" [email protected]
A "Discussion of precise time and frequency measurement"
[email protected]
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:[email protected]] 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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