[time-nuts] Notes on tight-PLL performance versus TSC 5120A

John Miles jmiles at pop.net
Thu Jun 3 08:36:55 UTC 2010

> On 3 June 2010 15:46, Bruce Griffiths <bruce.griffiths at xtra.co.nz> wrote:
> > WarrenS wrote:
> >>
> >> As Bruce says "It remains a mystery"  to him why this works.
> >
> > It doesnt, it only appears to in a very restricted set of circumstances.
> Bruce, I don't understand you, when presented with visual evidence
> that this method works you still deny it.

To be fair, we tested a couple of different sources, but we didn't encounter
every possible noise slope that might be found in the real world.  The 5062C
test is a good one, I think, but it's not exactly a closed-form proof.

The questions of what integration technique and what filter kernel are
optimal are not completely nailed down, IMHO.  I think the results we saw in
these tests show the process is adequate for 99% of all practical purposes,
but it is reasonable to demand a more exhaustive mathematical justification
if you're sending something to Mars.

The rectangular frequency-to-phase conversion is straight out of W. J.
Riley's manual, so I'm not very concerned about it, but the actual transfer
function we get by averaging the data prior to decimation is poorly
specified at best, and it's reasonable to put some more work into the
filtering side of things.   This is not an area I'm qualified to talk much

-- john, KE5FX

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