Steve Rooke wrote:
On 5 June 2010 19:07, Bruce Griffiths<bruce.griffi...@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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