On 6 June 2010 10:21, Bruce Griffiths <[email protected]> wrote: > Steve Rooke wrote: >> >> On 5 June 2010 19:07, Bruce Griffiths<[email protected]> 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.
Ah, the pathetic attempts to discredit opposition through insults and dismissal. This is the desperate attempt of a man grasping at straws trying to prevent going under. First they ignore you, then they mock you, then they fight you, then you win... Indeed, it does seem that the effects of the PLL are well understood by some but perhaps others have yet to learn. We seem to have got over the integration issue by remembering our our pre-calculus-101 dividing the area under a graph into strips, oversampling, to perform integration of a polynomial or any graph shape for that matter. > 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. Wrong again! And now a new red herring rears it's ugly head. So what have we here then, "low pass filtering built in", well this forms the biasing circuit of the varicap diode. The varicap itself forms part of the tuned circuit with the crystal acting as an inductor in this colpits oscillator Seeing as how that's the case, the hot end of the varicap which is connected to the EFC control via a resistor is in fact oscillating at 10Mh, having a period of 10^-7s, directly against that EFC feed. Now, considering that Warren's daq can only achieve a rate of about 400 sps, 2.5x10^-3, it is extremely unlikely that the "low pass filtering built in" will have any bearing on this matter. >> 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. Maybe Warren is not the person who is confused here. > A clear description of the details of the actual signal processing used is > sadly lacking. What need for "signal processing" is there? Is this some way that you feel there is a need to "massage" the results of actual measured data. I think there was a very loud discussion about "massaging" and "processing" data in a very large issue that came up a while ago. > If and only if the average is calculated sufficiently accurately. So, say, 10 samples of the EFC voltage are taken over time T, then the average of the samples is the sum of the samples / T. This is the principal of oversampling and I cannot see why there is any continued discussion on this point. > Using a rectangular approximation with sampled data may not be as accurate > as one may expect. Well, if we had an infinite number of samples over time T then we would have an absolutely accurate answer. Is this your point I wonder, so it has to be infinitely accurate, let alone and other points of error in the system which will obviously swamp this out like errors in the reference oscillator which are impossible to resolve because no one has yet come up with with an oscillator which is accurate to 1 / 10^(infinity). So lets get real shall we, if we take ten samples of a waveform over a period and calculate the integral using the rectangular method the results will be very close to the Riemann integral. Don't take my word for it, try it for yourself. Perhaps you believe that the method adopted by other to integrate the measurement over the whole time period with a filter that has a wider BW than the fundamental (because it has to let noise through) would give a more accurate answer, even though its settling time is not optimal for the measurement time. > 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. And it never ceases to amaze me how some stick-in-the-muds think that what was done 50 years ago is the be-all and end-all of research in any field. I guess if we had sent some ships out to see if the Earth was flat and they did not come back, we should believe in our assumptions and think that they must have fallen over the edge of the Earth. I guess it's a good job that some intrepid researchers discovered that there was no edge to the Earth and found out that it was round. Mind you if they stopped there they wound not have understood they were wrong as some later researchers found it was an oblate spheroid. And we are back to "correct processing" again, for some reason the measured data seems to need some form of manipulation. Well, you are correct to a certain extent, the oversamples need to added together and divided by the oversample rate. That is all the processing needed, just some logical processing of the data as part of the ADEV calculation. > The $10 cost is also misleading as the mixers aren't free nor is the 10811 > or its equivalent. But it's closer to $10 than a TSC or a dual mixer setup. > The assertion that this technique is new seems to be somewhat dubious as it > appears to have been known for several decades. So who has made this assertion, all along it's been understood that this was an improved way of implementing the tight-PLL method. Did you not get that? Now I'm finding this petty attack on someone else's research, without fully understanding it, quite tiresome, it's seriously cutting into my quality porn time but won't lay down and play dead. Regards, Steve -- Steve Rooke - ZL3TUV & G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
