[time-nuts] Tight-PLL - YOU DON'T NEED TO READ IT IF YOUR FED-UP WITH THE THREAD SO HIT DELETE NOW!

Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat Jun 5 18:21:32 EDT 2010


Steve Rooke wrote:
> On 5 June 2010 19:07, Bruce Griffiths<bruce.griffiths at xtra.co.nz>  wrote:
>    
>> Wrong again.
>>      
> No, I'm not wrong Bruce.
>
>    
Your "contribution" is largely irrelevant to the original discussion.
The effect of the PLL itself is (or should be) well understood.

However various assertions about the minimum usable value of Tau take no 
account of the low pass filtering built into the 10811 EFC circuit.
The 100k series resistors plus the capacitance of the EFC varicap 
(50-100pF??) will limit the minimum usable value of Tau.

>> The integration/averaging referred to occurs when one counts the output
>> transitions of the VFC for a fixed time interval.
>> This process needs to be replicated using the sampled EFC data if one is to
>> measure ADEV.
>>      
> This process is exactly replicated by oversampling the EFC and
> determining the average for a fixed time period.
>
>    
A various times Warren has both claimed to do this and at others appears 
to deny it.
A clear description of the details of the actual signal processing used 
is sadly lacking.

If and only if the average is calculated sufficiently accurately.
Using a rectangular approximation with sampled data may not be as 
accurate as one may expect.

It never ceases to amaze me why the well established and more accurate 
methods known aren't used (details are all given in the paper I cited), 
all it requires is a suitable program running on a PC.  The correct 
processing should have no effect on the hardware cost.
The $10 cost is also misleading as the mixers aren't free nor is the 
10811 or its equivalent.

The assertion that this technique is new seems to be somewhat dubious as 
it appears to have been known for several decades.

> If you can't see that this performs exactly the same function, I don't
> know what will convince you.
>
> Steve
>
>    
Bruce





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