[time-nuts] Measuring ADEV using TBolt-Tic tester

[ws at Yahoo]

Using the 1 sec ADEV noise floor from the plot at
 http://www.febo.com/pipermail/time-nuts/attachments/20111007/48d1ab68/attachment-0001.gifthis shows the RMS sum of the short term GPS signal's noise Plus the Tboltengine, plus the Osc, for the achievable resolution at 1 second.The "one shot", 1second resolution of the Tbolt's phase data is 100 ps orlessThe "one shot", 1 second resolution of the Tbolt's PTT detector is 10 ps orlessWhat is not too clear is how much of that is due to the Tbolt engine and howmuch is the "GPS Reference".From what I've seen in my test, a large amount of that noise floor is due tothe GPS.In these cases the Tbolt's external Osc noise is low enough as not tocontribute significantly to the RMS sum.This is not necessary an equal comparison to your 1 shot numbers, becausethe Tbolt is using high speed averaging to get its low "single shot" 1second resolution by averaging over many cycles of a higher frequency.Using this basic technique and averaging over 10,000 cycles of the 100ns10MHz signal, the "one shot" resolution achieved by the TPLL2.0 is under 10femtoSecond in 1ms.ws*************----- Original Message -----From: "Azelio Boriani"> The HP58503A has the Oncore 8-channel GPS receiver. The single-shot> resolution capability is the ability to resolve the time interval> without any averaging. For example, the Fluke/Pendulum PM6681/CNT81> has a 50pS resolution, the HP5370 has 20pS, the Racal Instruments 2351> VXI TIC has 8pS single shot maximum resolution, the Wavecrest SIA3000> signal analyzer has 200 femtoS hardware resolution at 3GHz.>**********************> On 10/13/11, ws at Yahoo wrote:>> I know very little about the HP58503A. Any chance it is using the old 6>> channel Oncore GPS engine?>> If it is like the Oncore I tested long ago, that noise was about a decadeor>> so higher than the Tbolt's phase noise.>>>> Not sure what you can call single-shot resolution. The data is reportedwith>> Pico second  resolution.>> The cycle to cycle max phase varation, If there is not a satellite changeat>> the same time, is around  0.4ns  max error.>> With the very high resolution that is output, averaging  provides a lotof>> benefit.>> The noise of the Tbolt's freq (PPT) output data measured about ten times>> lower than it's phase output data at 1 sec.>> How it does it is anyone guess, but looks to be some sort of high speed>> averaging going on, taken over a one second time interval.>>>> ws>>>> *****************>> ----- Original Message ----->> From: "Azelio Boriani">>>>> Your work is very interesting, now I wonder what is the Tbolt>>> single-shot resolution? Does the Tbolt use the analog interpolator>>> method? I don't have the Tbolt, I have an HP58503A at work as the only>>> reference.>>>