[time-nuts] Advantages & Disadvantages of the TPLL Method

[Robert Benward]

Warren,
I'm a newbie, so can you explain it to me?  Femto anything is something 
mostly reserved for a well equipped lab.  How do you do it when most digital 
logic has jitter several of orders of magnitude greater?

Bob


----- Original Message ----- 
From: "WarrenS" <warrensjmail-one at yahoo.com>
To: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Friday, June 18, 2010 3:58 PM
Subject: Re: [time-nuts] Advantages & Disadvantages of the TPLL Method


> Charles posted
>
>> its operation needs to be characterized if technically oriented folks are
>> to be expected to take you seriously.
>
> If a simple BB that works as well as that one, does not already do that,
> then nothing else I'm able or willing to do or say is going to change 
> much.
> It is a good thing that people can accept things when shown that they 
> work,
> even when they do not fully understand how.
> Or else there would no acceptance of much of anything including gravity,
> computers, email,  women or Windows.
>
> So your point is?  and why do you think I care?  Maybe you are missing the
> point of my intended audience.
> After all, I'm not the one that is lost or the one that does not know now 
> it
> works. I have a working unit that, I know how it works and how to test it.
>
>
>> how you determined phase locking down to femtosecond levels, & ...
>
> You do indeed have many valid technical questions that I'd try and explain
> in a way that you could understand,
> IF my goal was still to try and educate you, or if I thought there was ANY
> chance I'd be able to do so.
> You seem to again of missed the point of my last answer,
> One with enough technical ability can see what John's data says from his
> noise floor measurements.
> But
> If you do not understand that or how I'm doing it by measuring the PD
> output, then
> I can not teach or show you how, even if I still wanted to try. My past
> failed attempts prove that.
> So I'll just continue to do what I do best, and that is to make and test
> TPLL BBs for myself.
>
> If you were thinking that I am one that can or am willing to try and teach
> you basic or advanced anything, then you are greatly over estimating my
> abilities and/or my patience. You need to look else where if you want to
> read a fancy math paper on how and why this all works or how to measure 
> it.
> If you can't find one to your liking and still want to know how to measure
> fs stuff, I'm sure if you ask nicely in a new thread, others would be more
> than willing to help you out with something that you could understand and
> accept.
> Then again if I missed your point and your only goal is to verify if I now
> how to do it, then I can save you some trouble,
> Yes the TPLL and I know how to measure fs phase differences, and we both
> know how to integrate along with a lot of other basic things including 
> even
> adding two plus two.  (and I doubt that you understand that last point
> either, & Don't take it so personal, It is likely not just your problem)
>
> BTW, one of the other points you seem to be missing in how I can measure &
> test things so easy that others can find so hard to do.
> After all I do have a big advantages over most, I can use another one of 
> my
> GP PLL BB as a tester.
> As I've point out before, they can do much more than just ADEV.
> But then you would not be expected to know that without an advantage list.
>
>
> ****
> Seems like it is again 'Time to Push the Reset.Button' on this thread's
> subject, cause this has got way off the subject.
> As long as it is so far off the subject of advantages & disadvantages, 
> I'll
> add, in response to what others have said both on and off line.
>
> IF others want to build a TPLL using buffer amps, or VFC, or difference 
> Ref
> Osc, or multiple Ref osc, or a digital version or with cross correlation, 
> or
> using different software, or different algorithms, or different 
> connectors,
> or more parts,  or more expensive parts or cheaper parts, or that works
> better with some imaginary unreal data set, or over a wider freq range, or
> over a longer tau, or at a lower level, or with less injection locking, or
> any of the other thing's that have been brought up,
> by all means, Go for it. I've tried to encourage others to do it their 
> your
> own way. No single solution is best for all situations.
>
> What several of the suggestions show is that many do not yet know how 
> simple
> a TPLL can be made or do they even understand exactly how the 3 basic 
> parts
> work together.
> I have consider all the suggestions and tried many of them and so far have
> found the variations unnecessary for my applications.
> Also I have not heard about any H/W that others have built, only a lot of
> criticism from some about what I've done or said or not said.
> No problem, If others do not like what I've done or the way I've done it 
> or
> tested it, even when many of them do not know what it is or how it works,
> by all means they should do it there own way.
>
> What I've done is to test one of my simple TPLL versions and show that 
> it's
> performance is good enough to be limited by the OCXO.
> That is all, Don't read more into my comments than that.
> The simple TPLL does not go down to 1e-15.  What I said is that is the 
> limit
> of the low cost AMP that I choose, and it insures the amp has no 
> significant
> negative effect.
> Of course all is not perfect, nor is this is the best that a TPLL can be
> made, not even close. But it is good enough for me.
> I know how to made it better, much better, with lower noise, more
> resolution, faster, lower tau, smaller or bigger, more costly or lower 
> cost,
> and on & on.
> So what?, the achieved goal of 'KISS' was to keep it small, simple and low
> cost,  and make it good enough to test the high end OXCOs that are
> available.
>
> This simple $10 version (my ebay cost) of a TPLL tester using just a 
> single
> powered active part (not counting the Ref or the ADC or the PC) has plenty
> of limitations but it  has been show to be good enough to closely match a
> TSC 5120A over a wide range of signals.
> By all means if your needs, skill levels, experiences, desires, goals, and
> junk boxes are different than mine, and you want to make something 
> different
> or better, then by all means 'Go For It'.
>
> I'm not trying to tell anyone what method to use, or what they should 
> build
> or how to build one OR how to test it.
> I'm just trying to get a list posted to show the many unknown advantages 
> and
> disadvantages of the TPLL methods.
> Because so few have had any experience with this method and therefore have
> little or no practical knowledge about it.
> How can one go about deciding it is something is useful for them without
> knowing  what the advantages and disadvantages are?
>
> ws
>
> ***********************
> *************************
> [time-nuts] Advantages & Disadvantages of the TPLL Method
> Charles P. Steinmetz charles_steinmetz at lavabit.com
> Thu Jun 17 15:02:12 UTC 2010
>
> Warren wrote:
>
>>>I'm curious how you determined that the oscillators are being held
>>>to within femtoseconds of each other.
>>
>>I done  it several ways including measuring the PD output.
>>
>>You seem to be missing how insignificant an 1-e6 injection locking
>>to EFC gain ratio is.
>>I can't detail, to your satisfaction, all the hundreds of test that
>>show no significant effect of so many different things.
>>
>>For an independent test that may help you with things you missed see:
>> http://www.ke5fx.com/tpll.htm
>
> There you go again, accusing someone else of missing something.  I
> have never said I thought your method doesn't work.  I said its
> operation needs to be characterized if technically oriented folks are
> to be expected to take you seriously.  "See, it works!" is just not
> sufficient characterization to achieve this, IMO, and that is all you
> seem to offer -- references to John's tests included.  I inquired how
> you determined phase locking down to femtosecond levels, and all you
> can say is that you "measured the PD output" among other
> ways.  That's like a cosmologist saying (s)he "measured the positions
> of some stars, among other things" to determine the gravitational
> constant, which is fine for an interview in People magazine but
> inadequate for a technical audience.  What phase detector did you
> use?  What are its characteristics and limits?  With what did you
> measure its output?  What results did you get (at the very least, a
> descriptive summary of your dataset)?  How do those results support
> an inference of locking to within femtoseconds?  What other ways did
> you use to determine locking error besides measuring the PD
> output?  You imply that the ratio of the injection gain to EFC gain
> in your system is 1E-6.  How did you measure the injection
> gain?  What were the results (at the very least, a descriptive
> summary of your dataset), and how do they support an inference to the
> 1E-6 figure?
>
> Best regards,
>
> Charles
>
>
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