[time-nuts] A philosophy of science view on the tight pll discussion
sar10538 at gmail.com
Mon Jun 7 13:36:38 UTC 2010
There is much to learn and there will always be much to learn, we only
have to look at history for examples of this. Providing we never loose
understanding of this point, our path to enlightenment will always be
On 5 June 2010 23:58, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> On 06/05/2010 01:19 PM, Steve Rooke wrote:
>> So, at best, it's an estimate.
> How good it is, how fast you get it, how much you pay for it and how much
> effort it is to get and operate is the issue.
> Getting accurate measurements is hard to prove actually. Getting
> sufficiently good relative measurements (for money, effort etc) is easier
> most of the times.
> So what we have to do is to study various forms of impairments, learn their
> effects, learn how to deal with them and learn how various approaches have
> benefits and defficiencies. The deeper I study this, and the more of the
> things I have initially ignored but forced myself to follow up, the more
> complex the issue becomes and things comes in a different light. You get
> humbled by learning just how little you knew as you learn more. It is a
> time-consuming effort, but I hope some of it pays of in my contributions to
> the Allan variance article on Wikipedia.
> I have still not delivered a complete view from the things I have learned
> recently, even if I hint some of it. There is a number of statements in
> there which is unsatisfactory in that they do not have a complete inline
> reference, but I think I have done a fairly god job so far.
> Few people seems to estimate the values of h_-2, h_-1, h_0, h_1 and h_2 even
> if both phase noise and time/frequency difference data may be used for it.
> Also, modern cheap programmable TCXOs break the model as they have a hump in
> the phase noise due to their locked PLL, which the original model does not
> allow for. The autocorrelation function will be quite different. Notice how
> this ripples over to other locked oscillators such as passive masers, GPSDO
> There is still basic research to be done and basic research to be recovered
> from the archives.
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Steve Rooke - ZL3TUV & G8KVD
The only reason for time is so that everything doesn't happen at once.
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