[time-nuts] Question about frequency counter testing

[Bob kb8tq]

Hi

Consider a case where the clocks and signals are all clean and stable:

Both are within 2.5 ppb of an integer relationship. ( let’s say one is 10 
MHz and the other is 400 MHz ). The amount of information in your 
data stream collapses. Over a 1 second period, you get a bit better than 
9 digits per second.  Put another way, the data set is the same regardless 
of where you are in the 2.5 ppb “space”. 

Bob



> On Apr 27, 2018, at 5:30 AM, Hal Murray <hmurray at megapathdsl.net> wrote:
> 
> 
> olegskydan at gmail.com said:
>> No, it is much simpler. The hardware saves time-stamps to the memory at each
>> (event) rise of the input signal (let's consider we have digital logic input
>> signal for simplicity). So after some time we have many pairs of {event
>> number, time-stamp}. We can plot those pairs with event number on X-axis and
>> time on Y-axis, now if we fit the line on that dataset the inverse slope of
>> the line will correspond to the estimated frequency. 
> 
> I like it.  Thanks.
> 
> If you flip the X-Y axis, then you don't have to invert the slope.
> 
> That might be an interesting way to analyze TICC data.  It would work 
> better/faster if you used a custom divider to trigger the TICC as fast as it 
> can print rather than using the typical PPS.
> 
> ------
> 
> Another way to look at things is that you have a fast 1 bit A/D.
> 
> If you need results in a second, FFTing that might fit into memory.  (Or you 
> could rent a big-memory cloud server.  A quick sample found 128GB for 
> $1/hour.)  That's with 1 second of data.  I don't know how long it would take 
> to process.
> 
> What's the clock frequency?  Handwave.  At 1 GHz, 1 second of samples fits 
> into a 4 byte integer even if all the energy ends up in one bin.  4 bytes, *2 
> for complex, *2 for input and output is 16 GB.
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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