[time-nuts] Tight PLL method. Is it good enough?
sar10538 at gmail.com
Sun Jun 6 10:32:05 UTC 2010
On 5 June 2010 09:48, John Green <wpxs472 at gmail.com> wrote:
> I am a relative outsider to this fine group. I mostly just read the posts. I
> have learned a lot since I have subscribed.
> So, I don't have a dog in the fight over whether the tight PLL method is all
> Warren says it is. I can understand that Warren
> has researched this method, discovered its weakness and made advancements to
> compensate. He has tested it against
> a well known and respected piece of commercial gear and found good, though
> not perfect agreement. An achievement to be
> proud of. Bruce has also researched this method and sees that it has
> weaknesses. Some of which he feels Warren has not
> addressed. He is frustrated because Warren won't agree that there are
> problems with this method.
Better back the bus up there, Bruce has NOT researched THIS method but
still feels the need to make derisive comment.
> As someone who merely wants to test some oscillators, I am mainly interested
> in finding components I can buy and assemble
> into something I can have a modicum of confidence in. I was looking at doing
> a DMTD setup because I have most of the
> necessary components. But Warren has gotten my attention. By testing it
> against a piece of commercial equipment, he has
> gotten me to believe that if I build a similar setup, I can achieve similar
> results. The interesting thing is that his setup is relatively
> simple. I could probably duplicate it pretty closely. Is it perfect?
> Probably not. Would it do what I need done? Probably so.
That's the good part, time-nuttery for the masses, the people who
don't have the same budget as NIST. The other interesting thing is
that it does produce very slightly different results than the very
expensive equipment. So is the very expensive equipment always right,
well it costs enough to be right, it has a badge on it that would
indicate it is right and there is a very technical paper on how it
works that says it is right. So it's getting it right, right...
For all intents and purposes of probably what you and I want to do it
will be the right solution. You will want to obtain relative
comparisons between the sources you have and you will want to see if
anything that you have done has improved or degraded them. As for
absolute measurements, it certainly seems that for some Tau, there is
excellent correlation with the very expensive equipment. Yes there is
some discrepancy for long Tau and this is something of great interest
to some of us. I'm certainly very interested in this whole thing and
have put some considerable brain hours into it now. The basic
principal being used has been fully understood and accepted for
decades now but there has been problems with some ways it has been
implemented in the past. What has been researched by Warren is a very
slightly different way of implementing it which should resolve those
problems, that's all. The principal is exactly the same it's just the
measuring element which has been tweaked to make it easier to
implement and quite possibly produce more accurate results.
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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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