Re: [time-nuts] pps vs. 10 MHz timing
Are you using terminations or is the end equipment properly terminating ? Mismatched impedance does weird things to waveforms. Also check to make sure you not overdriving on your source. And a bad power supplies can induce waveform distortion. Brian Matt Ettus wrote: > > > Also, I noticed that the TADD-1 has some weird distortion of a 10 MHz > sine wave. It turns it into a sort of a 3 valued square wave. > Essentially, it stops and dwells at the midpoint for a while instead > of making a sharp transition. I think this would be bad if that dwell > point is close to the threshold for the receiving device. Has anyone > else noticed this? > > > Thanks, > Matt > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Date codes on hp 5071a?
The date code is not a production date, necessarily, but the date of that particular design revision (presumably when it was released to manufacturing). It sets a lower bound, but your unit could potentially be several years newer. You can get a better idea by looking for the latest date code on various ICs and capacitors. -- john, KE5FX > -Original Message- > From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on > Behalf Of Bruce Griffiths > Sent: Thursday, December 11, 2008 8:33 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Date codes on hp 5071a? > > > aceamuseme...@mchsi.com wrote: > > > > Hi,I was wondering by chance if someone familiar with hp date > coding could tell me the date of manuf. of this 5071a > > > > 3608A01190 > > > > Thanks, > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > Manufactured in USA during 8th week of 1996 > > Bruce > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Date codes on hp 5071a?
Thanks, I just purchased this on ebay and was just wondering how bad the tube could be(yrs left) I have a agilent one now I got new a year ago and its ion pump current keeps rising,the one advertised says its still pretty low @ 2.0uA ,1450emult..has telcom options installed so I bet it has lots of hrs but may be good for a few yrs? -- Original message from Bruce Griffiths : -- > aceamuseme...@mchsi.com wrote: > > > Hi,I was wondering by chance if someone familiar with hp date coding > > could > tell me the date of manuf. of this 5071a > > > > 3608A01190 > > > > Thanks, > > ___ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > > > Manufactured in USA during 8th week of 1996 > > Bruce > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Date codes on hp 5071a?
aceamuseme...@mchsi.com wrote: > > Hi,I was wondering by chance if someone familiar with hp date coding could > tell me the date of manuf. of this 5071a > > 3608A01190 > > Thanks, > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > Manufactured in USA during 8th week of 1996 Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Date codes on hp 5071a?
Hi,I was wondering by chance if someone familiar with hp date coding could tell me the date of manuf. of this 5071a 3608A01190 Thanks, ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] pps vs. 10 MHz timing
Hi Matt, > What do other GPSDOs do? All over the map. A well-engineered GPSDO might choose to align the rising zero crossing of the 10 MHz sinewave with the leading edge of a very fast risetime 1PPS, because this is "common sense" but if it isn't in the spec, it's best not to expect it to happen. > Clearly, any device trying to latch the 1 PPS signal using the 10 MHz > clock will need to choose which clock edge to use, depending on which > type of GPSDO is used. How is this normally handled? But worst case, if you chose the wrong 10 MHz sinewave edge you're at most 50 ns off from the 1PPS -- and note this is still within the +/- 100 ns of UTC accuracy spec that a lot of GPS receivers claim. There is often a fixed phase delay between the two outputs. It may be just a few ns or it may be tens of ns depending on the number of inverters, buffers, amplifiers in the signal path(s), the length of internal or external cables, or impedance effects on risetime (50R vs 1M can make a difference). One also has to be very careful with the 1PPS pulse itself. Most GPSDO do not specify the voltage level of the pulse. Now if the pulse risetime is just a couple of ns this is not a serious problem. But when the risetime is many ns or many tens of ns then you need to know what trigger voltage level constitutes the intended true moment of the 1PPS. See, for example, http://www.leapsecond.com/pages/gpsdo-rise/ Some of these GPSDO have about a 1 V / 10 ns slew rate which means if you don't nail down your trigger level you're asking for very large shifts in 1PPS timing. The zero-crossing of a 10 MHz sinewave doesn't have the same ambiguity. /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] pps vs. 10 MHz timing
Matt For those GPSDOs which also use the OCXO clock to generate the LO for the GPS receiver (eg Thunderbolt) the zerocrossing transitions of the 10MHz output are accurately aligned to the leading edge of the 1PPS output. For other GPSDOs there may be an offset between the 10MHz zero crossing and the receiver 1 PPS output. If the PPS output is derived from the OCXO via a divider then the leading edge of the PPS output will be aligned (within a gate propagation delay or 2) with the PPS output. One can always use a dual phase synchroniser to detect the 1Hz transition using the 10Mhz output. Bruce Matt Ettus wrote: > On my Oscilloquartz GPSDO, the 10 MHz output goes low at very close to > the same time as the 1 PPS output goes high. > > On my Fury, the 10 MHz sine wave is just dropping off of its max high > voltage as the 1 PPS goes high. The 10 MHz CMOS output goes high just > shortly before the 1 PPS. > > What do other GPSDOs do? > > Clearly, any device trying to latch the 1 PPS signal using the 10 MHz > clock will need to choose which clock edge to use, depending on which > type of GPSDO is used. How is this normally handled? > > Also, I noticed that the TADD-1 has some weird distortion of a 10 MHz > sine wave. It turns it into a sort of a 3 valued square wave. > Essentially, it stops and dwells at the midpoint for a while instead > of making a sharp transition. I think this would be bad if that dwell > point is close to the threshold for the receiving device. Has anyone > else noticed this? > > > Thanks, > Matt > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] pps vs. 10 MHz timing
On my Oscilloquartz GPSDO, the 10 MHz output goes low at very close to the same time as the 1 PPS output goes high. On my Fury, the 10 MHz sine wave is just dropping off of its max high voltage as the 1 PPS goes high. The 10 MHz CMOS output goes high just shortly before the 1 PPS. What do other GPSDOs do? Clearly, any device trying to latch the 1 PPS signal using the 10 MHz clock will need to choose which clock edge to use, depending on which type of GPSDO is used. How is this normally handled? Also, I noticed that the TADD-1 has some weird distortion of a 10 MHz sine wave. It turns it into a sort of a 3 valued square wave. Essentially, it stops and dwells at the midpoint for a while instead of making a sharp transition. I think this would be bad if that dwell point is close to the threshold for the receiving device. Has anyone else noticed this? Thanks, Matt ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sub Pico Second Phase logger
Joe Attached is noise spectrum (1kHz and below) of AP192 with nothing connected to inputs. Sampling rate 96KSPS. Frequency bin equivalent noise bandwidth ~ 3Hz. Noise has similar spectrum to flicker noise with a noise corner of around 300Hz or so. Bruce <>___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sub Pico Second Phase logger
Joe Isolation from mixer RF to LO port may be too low when the mixer input frequencies are different. Injection locking can then occur all too easily (just ask Ulrich about this) when the mixer RF ports are driven by 2 separate OCXOs. Detailed in line post follows: Bruce Joseph M Gwinn wrote: > Bruce, > > > time-nuts-boun...@febo.com wrote on 12/10/2008 08:38:13 PM: > > >> Joe >> Joseph M Gwinn wrote: >> >>> Bruce, >>> >>> >>> Reflecting the sum frequency back into the mixer is actually > necessary > to reduce the noise at the IF port. I believe that one of Agilent's simulation application notes mentions this effect but I don't recall the actual application note number. This will affect the mixer RF and IF port impedance so adding a > series > resistor may be required to improve the SWR. >>> How big an effect is this? Is the absolute noise decreased, or does >>> > it > >>> remain the same while the signal increase? >>> >>> >>> >> With the same difference frequency IF port termination impedance, noise >> is actually decreased along with the mixer conversion loss. >> > > OK. Complicated beasts, those mixers. Do you know of a paper (or book) > on the subject? > > Not offhand, but this crops up in lots of places usually when one least expects it.. >> However if the sound card input noise dominates, reducing the mixer >> effective output noise won't help. >> > > Yes. In the plots you posted in a different email, there was a big rise > below 1 KHz (scan stopped at 1 KHz, so don't know the shape). Why is > this? > > > I'll expand the frequency scale and take another snapshot for the region below 1kHz. This rise may be due to ADC and/or input differential amplifier flicker noise. >>> If I'm understanding Walls and Stein (paper 112) correctly, the >>> > advantage > >>> is because with the capacitor load the beatnote waveform approaches >>> square, thus increasing the zero-crossing speed and therefor the phase >>> > > >>> sensitivity. This is no doubt true, but the question was if this also >>> > > >>> caused a small everything-dependent phase shift, something that would >>> > not > >>> have mattered in the measurement of phase noise. The object of paper >>> > 112 > >>> was to remedy a 10 to 20 dB error in phase noise measurements. The >>> critical words are in the lower left column of page 337, in the >>> > paragraph > >>> beginning "If the mixer is terminated ...". >>> >>> >>> >>> >> Saturating the RF port has a similar effect. >> > > Yes. But there are tradeoffs pushing the other way. > > > >> If one is time stamping the zero crossings an increased zero-crossing >> > slope is an advantage. > >> For relative phase measurements a trapezoidal beat frequency waveform >> > may be less useful. > > Fitting to the approximate waveshape, sine or trapezoidal, should yield a > very robust estimate, due to the large data support, and zero-crossing > slope won't much matter. Hmm. Actually, if the slopes of the trapezoid > are too steep, we may not have all that many slope samples. > > > If one believes the NIST papers the trapezoid zero crossing slope only increases by a factor of 3. If one uses a cascaded filter limiter the slope gain can be adjusted for optimum results. > [snip] > >> Of course with a capacitive IF port termination, matching the RF and LO >> ports becomes more critical as does the reverse isolation of the various >> amplifiers driving the RF and LO ports. >> It may be simpler in fact to use a level 17 mixer with high LO to RF and >> LO to IF isolation with the RF port unsaturated as it relaxes the >> reverse isolation specs for the isolation amplifiers. >> > > Another tradeoff. I'll have to think about it. > > I'm thinking of 6 db and 10 db attenuators on the LO and RF ports > respectively, but no isolation amplifier. > > You may get away with that if you use mixers with very high RF to LO port isolation. Minicircuits have at least 3 level 17 mixer models that typically have 80dB LO to RF isolation at 10MHz. Using a passive splitter for the LO drives will gain at least another 30dB in isolation between the 2 RF inputs if you use an appropriate splitter. > [snip] > >>> >> The only configuration for which it makes any sense is an inverting >> input amplifier with a finite input voltage offset. >> > > Why would non-inverting not work? Both inputs source or sink bias > currents, and non-inverting presents a very high impedance. > > > > Non inverting amplifiers usually have lower noise and generally work very well. I was only trying to come up with a preamp circuit for which the comments in the Minicircuits application note on the effect of amplifier input offset voltage made any sense. The only risk with
Re: [time-nuts] time-nuts Digest, Vol 53, Issue 47
Ooooh, way to big, complicated, expensive, fragile, and swoopty fancy pants for real world use... The CG-3 type instruments and some of the the LaCoste & Romberg units also have ppb resolution and weigh around 12 kg. The Worden units weigh even less (and I bought mine for less than $100). The only problem with the Worden type devices is if you even think about jiggling it while the mechanism is unlocked you break the quartz fiber. The current method is to drop an optical corner cube (retro-reflector) in a vacuum and using a laser measure the distance it moves (which requires a reasonably good source of time. http://www.ngs.noaa.gov/GRD/GRAVITY/ABSG.html _ Suspicious message? There’s an alert for that. http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_broad2_122008 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sub Pico Second Phase logger
> > > The Symmetricom 5120A does something very clever to alleviate this > > > problem. Explained in US patent 7,227,346 and "Direct-Digital > Phase-Noise > > > Measurement"; J. Grove, J. Hein, J. Retta, P. Schweiger, W. Solbrig, > and > > > S.R. Stein; 2004 IEEE International Ultrasonics, Ferroelectrics, and > > > Frequency Control Joint 50th Anniversary Conference, pages 287-291. > > > > > > Joe > > > > > > > > I've read the patent. > > The paper is also worthwhile, and available on the web somewhere (don't > recall where, but google found the pdf). I had to read the patent > multiple times to figure out what's going on. The correlation > approach is > old as the hills, and only the digital phase detector was patentable. If you find a link to the Grove paper that's not behind an IEEE paywall, please post it. I'd like to read that one. -- john, KE5FX ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time-nuts Digest, Vol 53, Issue 46
Hi Mark: I think it's out of date. The current method is to drop an optical corner cube (retro-reflector) in a vacuum and using a laser measure the distance it moves (which requires a reasonably good source of time. http://www.ngs.noaa.gov/GRD/GRAVITY/ABSG.html Have Fun, Brooke Clarke http://www.prc68.com Mark Sims wrote: > The quintessential gravity meter (Worden Gravity Meter by Texas > Instruments)... still being made after 60 years or so: > http://www.mssu.edu/seg-vm/pict0246.html > > > -- > Geologists measure gravity to get the density of of the underlying rocks. I > saw a neat topo map of the San Francisco peninsula at one of the USGS open > houses. The contours were rock density rather than elevation. > > Of course, they had to correct for elevation. When I asked how they got the > elevation, the guy smiled: "From the sewer people". > > They had the instrument on display. It wasn't very big, say a cubic foot. > Maybe they will have it out at the next open house so I can look closer. > > > _ > Send e-mail anywhere. No map, no compass. > http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_anywhere_122008 > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sub Pico Second Phase logger
Bruce, time-nuts-boun...@febo.com wrote on 12/10/2008 08:38:13 PM: > Joe > Joseph M Gwinn wrote: > > Bruce, > > > > > >> Reflecting the sum frequency back into the mixer is actually necessary > >> to reduce the noise at the IF port. > >> I believe that one of Agilent's simulation application notes mentions > >> this effect but I don't recall the actual application note number. > >> This will affect the mixer RF and IF port impedance so adding a series > >> resistor may be required to improve the SWR. > >> > > > > How big an effect is this? Is the absolute noise decreased, or does it > > remain the same while the signal increase? > > > > > With the same difference frequency IF port termination impedance, noise > is actually decreased along with the mixer conversion loss. OK. Complicated beasts, those mixers. Do you know of a paper (or book) on the subject? > However if the sound card input noise dominates, reducing the mixer > effective output noise won't help. Yes. In the plots you posted in a different email, there was a big rise below 1 KHz (scan stopped at 1 KHz, so don't know the shape). Why is this? > > If I'm understanding Walls and Stein (paper 112) correctly, the advantage > > is because with the capacitor load the beatnote waveform approaches > > square, thus increasing the zero-crossing speed and therefor the phase > > sensitivity. This is no doubt true, but the question was if this also > > caused a small everything-dependent phase shift, something that would not > > have mattered in the measurement of phase noise. The object of paper 112 > > was to remedy a 10 to 20 dB error in phase noise measurements. The > > critical words are in the lower left column of page 337, in the paragraph > > beginning "If the mixer is terminated ...". > > > > > > > Saturating the RF port has a similar effect. Yes. But there are tradeoffs pushing the other way. > If one is time stamping the zero crossings an increased zero-crossing slope is an advantage. > For relative phase measurements a trapezoidal beat frequency waveform may be less useful. Fitting to the approximate waveshape, sine or trapezoidal, should yield a very robust estimate, due to the large data support, and zero-crossing slope won't much matter. Hmm. Actually, if the slopes of the trapezoid are too steep, we may not have all that many slope samples. [snip] > > Of course with a capacitive IF port termination, matching the RF and LO > ports becomes more critical as does the reverse isolation of the various > amplifiers driving the RF and LO ports. > It may be simpler in fact to use a level 17 mixer with high LO to RF and > LO to IF isolation with the RF port unsaturated as it relaxes the > reverse isolation specs for the isolation amplifiers. Another tradeoff. I'll have to think about it. I'm thinking of 6 db and 10 db attenuators on the LO and RF ports respectively, but no isolation amplifier. [snip] > > > > > The only configuration for which it makes any sense is an inverting > input amplifier with a finite input voltage offset. Why would non-inverting not work? Both inputs source or sink bias currents, and non-inverting presents a very high impedance. > > > >> It's hard to find such Firewire systems without such unnecessary frills > >> (for this application) as high gain preamps. > >> > > > > The AP192 has high-level inputs, but I don't know if this bypasses the > > preamps, or attenuates. Given their target market, I'd bet it bypasses. > > > > > There are no preamps other than an external differential input amplifier > that translates the 4 Vrms FS inputs at the input connector to a level > that the ADC can handle. > The ADC chip itself has no preamps built in. > There have been numerous complaint about this by some audio nuts, > however for this application not having such amplifiers is ideal. Bingo! Good to know. > >> The gain tempco and linearity of some variable gain audio preamps is > >> somewhat suspect. > >> > > > > I would think that none of these cards has a good tempco of anything, > > given the lack of necessity in their market. > > > > I would think that linearity would be quite good, given the horsepower > > competitions on linearity. > > > > > Since the 2 ADCs share the same reference their gain tracking tempco > should be quite good given that they use capacitors rather than > resistors within the ADCs. A happy accident, but we'll take it. We are converging on a soundcard wishlist: 1. True balanced inputs on XLR connectors. And good ground design, so we aren't bedeviled by ground loops. 2. 24-bit ADCs, and similar DACs. 3. Very good isolation all around. 4. Digital access via firewire (or USB3 I suppose), with the soundcard in its own box. 5. High-level input direct to the ADCs. While use of AKM ICs may be a very good idea, it is not a requirement per se. [snip] > >> Can alleviate [oddities at end of phase range} to some exte
Re: [time-nuts] Sub Pico Second Phase logger
Brooke The NIST papers concerned were about using mixers as phase detectors: http://tf.nist.gov/timefreq/general/pdf/112.pdf http://tf.nist.gov/timefreq/general/pdf/971.pdf As is all too often the case with some NIST papers the operating conditions for which the stated phase detection characteristics are true are not specified. Its probably a case of over familiarity with the subject and forgetting that what's obvious to the author isn't necessarily obvious to the reader. Since the Minicircuits phase detectors (RPD, MPD series etc) are specified for operation with a 500 ohm resistive IF termination, and they have relatively high RF port to RF port isolation changing the RF port termination from 50 ohms (at least with low frequency mixers using conventional transformers) doesn't necessarily degrade the port to port isolation significantly. Bruce Brooke Clarke wrote: > Hi Bruce: > > A general comments on mixers. > > Since they are very nonlinear devices the output consists of signals at: > +/-m * RF +/-n * LO. > The output will change if the termination on any of the ports at any of those > frequencies is changed. How much it changes depends on how strong that > signal > is. Some mixers reflect the image frequency to improve the conversion loss > of > the desired output. > > For the mixers I was working with the LO needed to be strong enough to drive > the diodes into saturation and the RF needed to be small enough to not effect > the LO power. > > More on that at: > http://www.prc68.com/I/Diodes.html > > Have Fun, > > Brooke Clarke > http://www.prc68.com > > Bruce Griffiths wrote: > >> Joe >> >> I suspect that the phase detector characteristics stated in the NIST >> papers only apply when the mixer RF port is saturated. >> This is evident from the Kurtz application note: >> >> http://www.wj.com/archive/documents/Tech_Notes_Archived/Mixers_phase_detectors.pdf >> >> which indicates (Figure 14 and Figure 15 plus surrounding text) that >> for a high impedance (resistive) IF port termination the phase detection >> characteristic only approaches a triangular wave when the RF port is >> saturated (Figure 15) whereas for an unsaturated RF port (Figure 14) the >> phase detection characteristics still appears sinusoidal. >> The Kurtz application note also indicates that the IF port signal >> amplitude reaches a maximum when the IF port termination resistance >> increases (for the particular mixer) above 400 ohms. >> >> There are no corresponding figures for the case of an IF port terminated >> in a capacitor. >> It would be interesting to check this. >> >> Saturating the RF port also degrades the isolation etc, thus another >> interesting question is does capacitively terminating the IF port >> degrade these parameters when the RF port is unsaturated? >> This may well not be the case with 5MHz or 10MHz mixer input frequencies. >> >> >> Bruce >> >> >> >> ___ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] V standards
And a newer design gravity meter: http://www.ipgp.jussieu.fr/files_lib/163_CG-3DescriptionTestResults.pdf _ Suspicious message? There’s an alert for that. http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_broad2_122008 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time-nuts Digest, Vol 53, Issue 46
The quintessential gravity meter (Worden Gravity Meter by Texas Instruments)... still being made after 60 years or so: http://www.mssu.edu/seg-vm/pict0246.html -- Geologists measure gravity to get the density of of the underlying rocks. I saw a neat topo map of the San Francisco peninsula at one of the USGS open houses. The contours were rock density rather than elevation. Of course, they had to correct for elevation. When I asked how they got the elevation, the guy smiled: "From the sewer people". They had the instrument on display. It wasn't very big, say a cubic foot. Maybe they will have it out at the next open house so I can look closer. _ Send e-mail anywhere. No map, no compass. http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_anywhere_122008 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPS signal simulator
>> One of the questions I've needed to answers is just how good is good enough >> when it comes to making a high performance GPSDO. >There is no single answer to this. One man's high-performance >is another man's low-performance. It all depends on where you >are in your quest. >> Some of the self build units I've heard being used can be 100 to 1000 or >> more >> times worse than desired for best performance. >> >> WarrenS >That is correct. Because time can be measured more precisely >than any other physical quantities it is quite normal for amateur >projects or even professional products to span many orders of >magnitude in performance. It is also true that the requirements >have as great a span. Someone needing a time source simply >for NTP (milliseconds) can get by with a solution a million times >less precise than someone trying to tune the C-field of their own >cesium standard (nanoseconds). > >/tvb My mistake, I should not of assumed as I did, that everyone would understand what "good enough" means for a "high performance GPSDO". Good enough means: so as NOT to degrade the limited and available accuracy of the GSP signal. i.e at least 3 to 6 db better than the noise. The correct answer is not a function of the user, it is a function of the GPS signal. Warren ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sub Pico Second Phase logger
Hi Bruce: A general comments on mixers. Since they are very nonlinear devices the output consists of signals at: +/-m * RF +/-n * LO. The output will change if the termination on any of the ports at any of those frequencies is changed. How much it changes depends on how strong that signal is. Some mixers reflect the image frequency to improve the conversion loss of the desired output. For the mixers I was working with the LO needed to be strong enough to drive the diodes into saturation and the RF needed to be small enough to not effect the LO power. More on that at: http://www.prc68.com/I/Diodes.html Have Fun, Brooke Clarke http://www.prc68.com Bruce Griffiths wrote: > Joe > > I suspect that the phase detector characteristics stated in the NIST > papers only apply when the mixer RF port is saturated. > This is evident from the Kurtz application note: > > http://www.wj.com/archive/documents/Tech_Notes_Archived/Mixers_phase_detectors.pdf > > which indicates (Figure 14 and Figure 15 plus surrounding text) that > for a high impedance (resistive) IF port termination the phase detection > characteristic only approaches a triangular wave when the RF port is > saturated (Figure 15) whereas for an unsaturated RF port (Figure 14) the > phase detection characteristics still appears sinusoidal. > The Kurtz application note also indicates that the IF port signal > amplitude reaches a maximum when the IF port termination resistance > increases (for the particular mixer) above 400 ohms. > > There are no corresponding figures for the case of an IF port terminated > in a capacitor. > It would be interesting to check this. > > Saturating the RF port also degrades the isolation etc, thus another > interesting question is does capacitively terminating the IF port > degrade these parameters when the RF port is unsaturated? > This may well not be the case with 5MHz or 10MHz mixer input frequencies. > > > Bruce > > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] V standards
Most of the industrial scales that allow location to be specified do it to improve out-of-the-crate accuracy where you might not have a calibration weight/cart/truck available (BTW, calibration carts are not used on the more accurate scales... things like bouyancy of the air in the tires can greatly affect the apparent mass). Most lab scales way to accurate to be able to effectively use a gravity model. They have built in calibration weights (or use external weights) that compensate for such things. I have not tried to see if I can see the tidal effect with my Mettler mass comparator (1 part in 100,000,000 res). I would suspect that it would be swamped by temperature fluctuations and the HUGE effect of air density (the weigh chambers on these beasties lies behind three layers of thermal glass to keep radiation of body heat, etc from stirring up air currents). At that level of resolution you are recalibrating the scale pretty much between evey reading. -Mark, That's very cool that they would model static gravity effects like that. Makes sense at that level of resolution. Do you know of any laboratory scales that also require you to enter the date/time so they can also model the dynamic 0.1 ppm effect on gravity of lunar/solar tides? /tvb ** Funny, Anyone out there that remember "True weight, no springs", and for a penny you also get your horoscope. Load cells have taken a big step backward. They use springs and therefore are measuring weight and not mass. This is why they need to be calibrate for the location they are at. Gravity can vary by more 0.1% from location to location, so a spring scale needs to be calibrated for a given location A mass scale, on the other hand, does not depend on gravity, and does not need to be calibrated for location, AND it can not be use to measure the change in Gravity due to tides etc.. WarrenS ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Sub Pico Second Phase logger
Joe I suspect that the phase detector characteristics stated in the NIST papers only apply when the mixer RF port is saturated. This is evident from the Kurtz application note: http://www.wj.com/archive/documents/Tech_Notes_Archived/Mixers_phase_detectors.pdf which indicates (Figure 14 and Figure 15 plus surrounding text) that for a high impedance (resistive) IF port termination the phase detection characteristic only approaches a triangular wave when the RF port is saturated (Figure 15) whereas for an unsaturated RF port (Figure 14) the phase detection characteristics still appears sinusoidal. The Kurtz application note also indicates that the IF port signal amplitude reaches a maximum when the IF port termination resistance increases (for the particular mixer) above 400 ohms. There are no corresponding figures for the case of an IF port terminated in a capacitor. It would be interesting to check this. Saturating the RF port also degrades the isolation etc, thus another interesting question is does capacitively terminating the IF port degrade these parameters when the RF port is unsaturated? This may well not be the case with 5MHz or 10MHz mixer input frequencies. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS signal simulator
> One of the questions I've needed to answers is just how good is good enough > when it comes to making a high performance GPSDO. There is no single answer to this. One man's high-performance is another man's low-performance. It all depends on where you are in your quest. > Some of the self build units I've heard being used can be 100 to 1000 or more > times worse than desired for best performance. > > WarrenS That is correct. Because time can be measured more precisely than any other physical quantities it is quite normal for amateur projects or even professional products to span many orders of magnitude in performance. It is also true that the requirements have as great a span. Someone needing a time source simply for NTP (milliseconds) can get by with a solution a million times less precise than someone trying to tune the C-field of their own cesium standard (nanoseconds). /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] V standards
> Do you know of any laboratory scales that also require you to enter > the date/time so they can also model the dynamic 0.1 ppm effect on > gravity of lunar/solar tides? It's worse than that. Geologists measure gravity to get the density of of the underlying rocks. I saw a neat topo map of the San Francisco peninsula at one of the USGS open houses. The contours were rock density rather than elevation. Of course, they had to correct for elevation. When I asked how they got the elevation, the guy smiled: "From the sewer people". They had the instrument on display. It wasn't very big, say a cubic foot. Maybe they will have it out at the next open house so I can look closer. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] V standards
Most of the industrial scales that allow location to be specified do it to improve out-of-the-crate accuracy where you might not have a calibration weight/cart/truck available (BTW, calibration carts are not used on the more accurate scales... things like bouyancy of the air in the tires can greatly affect the apparent mass). Most lab scales way to accurate to be able to effectively use a gravity model. They have built in calibration weights (or use external weights) that compensate for such things. I have not tried to see if I can see the tidal effect with my Mettler mass comparator (1 part in 100,000,000 res). I would suspect that it would be swamped by temperature fluctuations and the HUGE effect of air density (the weigh chambers on these beasties lies behind three layers of thermal glass to keep radiation of body heat, etc from stirring up air currents). At that level of resolution you are recalibrating the scale pretty much between evey reading. -Mark, That's very cool that they would model static gravity effects like that. Makes sense at that level of resolution. Do you know of any laboratory scales that also require you to enter the date/time so they can also model the dynamic 0.1 ppm effect on gravity of lunar/solar tides? /tvb _ Send e-mail faster without improving your typing skills. http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_speed_122008 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS signal simulator
- Original Message - From: "Tom Van Baak" To: "Discussion of precise time and frequency measurement" Sent: Thursday, December 11, 2008 7:10 AM Subject: Re: [time-nuts] GPS signal simulator >> Tom >> >> Thanks that should be very useful for software simulations. >> >> The use I had in mind for the tool I described where for the next stage of >> testing. >> It can be used to test at the REAL Hardware level, using a 'perfect' GPS >> signal with >> no noise or with any type of desired controlled noise. >> For example it is hard and time consuming to see how many ps of error >> your phase detector is adding or what the phase margin or noise gain is of >> the H/W PLL. >> Is the power supply good enough or is it causing errors, etc >> When using real GPS data, the random noise will hide the advanced >> type of information you may want to take. >> The other use of the Hardware simulator is for someone that wants to know >> how >> accurate their GPSDO is but does not have access to a source accurate enough >> to test their GPSDO. >> >> WarrenS > > Read a paper like this to appreciate the complexities involved: > > http://tycho.usno.navy.mil/ptti/ptti2002/paper29.pdf > > /tvb > ** TOM Thanks once again, The paper is very helpful, even if I can't yet say I understand it all. Agree, noise is a complex issue, GPS noise more so than most, because of all the many different types of contributing noise sources. That is the reason I like to remove those unknowns initially for my H/W test. Without adding the GPS noise to confuse the facts, it is very clear and easy to see, measure, and fix if desired the difference between say a sub ns accurate design and a micro sec unit. One of the questions I've needed to answers is just how good is good enough when it comes to making a high performance GPSDO. Some of the self build units I've heard being used can be 100 to 1000 or more times worse than desired for best performance. WarrenS ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] V standards
Mark Sims writes: > I am a bit of a mass nut (OK I have a LOT of digital scales > with resolutions down to a nanogram and up to 60Kg with > 0.01g res). Many of the industrial scales require you to > enter your lat/lon/altitude (or at least your general location) > so they can better model and compensate for gravity. > A 3 meter (1 story in a building) change in altitude affects >gravity by 1 part/million... easily noticeable on even a modest > analytical balance. Modern lab balances can easily resolve > 1 part in 20 million. The better ones exceed 1 part in 100 million. > Industrial scales can do 1 part per million of max capacity... > not too shabby for a mass to digital converter. Mark, That's very cool that they would model static gravity effects like that. Makes sense at that level of resolution. Do you know of any laboratory scales that also require you to enter the date/time so they can also model the dynamic 0.1 ppm effect on gravity of lunar/solar tides? /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] V standards
As far as DMM voltages standards, no need to build one for the 4.5 digit meters. Doug Malone sells an excellent Xicor based reference that runs off a 9V battery for around $30 shipped. Mine checks out to better than 0.5V on all my 6.5 and 7.5 digit meters. He sells them on Ebay under them user name zildjianboy7 (see item number 280292722286). There is also the Geller Labs unit, potentially more accurate, but it needs an external supply. It would be nice if they had 2.0V (or 1.9V) units available for checking those X.5 digit meters to better accuracy. I am a bit of a mass nut (OK I have a LOT of digital scales with resolutions down to a nanogram and up to 60Kg with 0.01g res). Many of the industrial scales require you to enter your lat/lon/altitude (or at least your general location) so they can better model and compensate for gravity. A 3 meter (1 story in a building) change in altitude affects gravity by 1 part/million... easily noticeable on even a modest analytical balance. Modern lab balances can easily resolve 1 part in 20 million. The better ones exceed 1 part in 100 million. Industrial scales can do 1 part per million of max capacity... not too shabby for a mass to digital converter. _ Send e-mail faster without improving your typing skills. http://windowslive.com/Explore/hotmail?ocid=TXT_TAGLM_WL_hotmail_acq_speed_122008 ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Trimble GPS Antenna's
Hi Roy: I have some info on what antennas are allowable for the ThunderBolt at: http://www.prc68.com/I/ThunderBolt.shtml#Ant Note the earlier Trimble Trimpack receivers needed 41 dB of gain between the antenna and receiver, but the Thunderbolt only needs 18 to 35 dB. Have Fun, Brooke Clarke http://www.prc68.com Roy Phillips wrote: > A question please . . . . . > > In all the considerable exchange of useful information regarding the Trimble > GPS units, I cannot recall any mention of the actual specification of the > antenna system for these units. My old Odetics used an "Active" antenna which > required 12 volts DC to be supplied from the unit and returned the signal in > the intermediate frequency range of 40 something MHz. I am aware that the > Trimble units also have "Active" antenna systems, which are supplied with +5 > volts DC, but what is returned from the antenna - - is this also an > intermediate frequency? > > I now have two antenna's awaiting better weather to install them on a single > storey building, including a 26dB gain Lucent, which are currently stuck on > temporary poles at approximately 15 feet/5 mts. I am surprised at the > relatively good performance in this temporary position. In fact I have had > the Trimble/NortelGPS unit working with GPS lock, with the Lucent antenna > standing in a glass jar in a north facing window (4 feet from ground level !) > . Propagation is certainly a very complex matter. > Roy Phillips > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Trimble GPS Antenna's
A question please . . . . . In all the considerable exchange of useful information regarding the Trimble GPS units, I cannot recall any mention of the actual specification of the antenna system for these units. My old Odetics used an "Active" antenna which required 12 volts DC to be supplied from the unit and returned the signal in the intermediate frequency range of 40 something MHz. I am aware that the Trimble units also have "Active" antenna systems, which are supplied with +5 volts DC, but what is returned from the antenna - - is this also an intermediate frequency? I now have two antenna's awaiting better weather to install them on a single storey building, including a 26dB gain Lucent, which are currently stuck on temporary poles at approximately 15 feet/5 mts. I am surprised at the relatively good performance in this temporary position. In fact I have had the Trimble/NortelGPS unit working with GPS lock, with the Lucent antenna standing in a glass jar in a north facing window (4 feet from ground level !) . Propagation is certainly a very complex matter. Roy Phillips ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] GPS signal simulator
> Tom > > Thanks that should be very useful for software simulations. > > The use I had in mind for the tool I described where for the next stage of > testing. > It can be used to test at the REAL Hardware level, using a 'perfect' GPS > signal with > no noise or with any type of desired controlled noise. > For example it is hard and time consuming to see how many ps of error > your phase detector is adding or what the phase margin or noise gain is of > the H/W PLL. > Is the power supply good enough or is it causing errors, etc > When using real GPS data, the random noise will hide the advanced > type of information you may want to take. > The other use of the Hardware simulator is for someone that wants to know how > accurate their GPSDO is but does not have access to a source accurate enough > to test their GPSDO. > > WarrenS Read a paper like this to appreciate the complexities involved: http://tycho.usno.navy.mil/ptti/ptti2002/paper29.pdf /tvb ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Voltage standards
One of those things that I've always wanted to do was to lash together a liquid air plant from, say, refrigeration parts. Never had the time and the funds at the same time. Looked at that 10-15 years ago when in the SFX business and we used a lot of LN2. You need a real high pressure compressor (e.g. Something like used for filling scuba tanks) for the classic technique. After fiddling with designs and poring over catalogs and surplus auctions, we decided it's cheaper and easier to just fill the GP45 for $100. But, it WOULD be fun... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] V standards
John, Yes, that is a common practice. Both scale factor TC and balance TC are inside the cell body. Usually it is a device similar to foill strain gage, (but made of nickel or balco alloy) and glued to the cell near the sg bridge. Micromeasurements.com (Vishay) has a lot on that topic. Predrag Dukic At 15:03 11.12.2008, you wrote: >On Sat, 29 Nov 2008 19:27:34 -0500, "Mike Monett" <[EMAIL PROTECTED]> >wrote: > > >This discussion of voltage standards is very informative and useful, and my > >thanks to all who are contributing. > > > >It is clear why precise frequency standards are needed - there are > >innumerable applications such as GPS, VLBI, secure spread spectrum radio, > >deep space navigation using doppler, and so on. > > > >But I wonder why extreme accuracy is needed in measuring voltage? Don't get > >me wrong - I have a HP 3456A, and I would love to have a 3458. But the > >prices on eBay can reach $6k, and I can't see spending that much money for > >two more digits. As Bill would say, six digits should be enough for > >everyone:) > >Because it's still an analog world out there. One instance that immediately >comes to mind are truck scales, especially the enforcement ones. I recently >serviced one that had a 200,000 lb capability, a 5 lb resolution and nailed my >personal body weight to within the resolution with no last digit dithering. >That indicates to me better than 2.5 lb internal resolution. > >Calibration of this particular scale is done in the digital world - roll a >50,000 lb calibrated trailer onto the scale, tell the scale processor that it >weighs 50,000.0 lbs and it figures out its own conversion factors. HOWEVER. >Servicing the thing means working down in the kind of precision levels we're >talking about. > >I have the 4 lightning-struck load cells and the matched summing box in my >shop ($10,000 from the scale company) so when I get time I can see how they do >it that precise with so few parts and with the load cells and summing box out >in the weather. There are only 4 wires coming from each load cell so the >temperature compensation has to be built into the mechano-electrical design >and not externally compensated. > >John >-- >John De Armond >See my website for my current email address >http://www.neon-john.com >http://www.johndearmond.com <-- best little blog on the net! >Tellico Plains, Occupied TN >In theory, there is no difference between theory and practice. In >practice, there is. > > >___ >time-nuts mailing list -- time-nuts@febo.com >To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] V standards
On Sat, 29 Nov 2008 19:27:34 -0500, "Mike Monett" <[EMAIL PROTECTED]> wrote: >This discussion of voltage standards is very informative and useful, and my >thanks to all who are contributing. > >It is clear why precise frequency standards are needed - there are >innumerable applications such as GPS, VLBI, secure spread spectrum radio, >deep space navigation using doppler, and so on. > >But I wonder why extreme accuracy is needed in measuring voltage? Don't get >me wrong - I have a HP 3456A, and I would love to have a 3458. But the >prices on eBay can reach $6k, and I can't see spending that much money for >two more digits. As Bill would say, six digits should be enough for >everyone:) Because it's still an analog world out there. One instance that immediately comes to mind are truck scales, especially the enforcement ones. I recently serviced one that had a 200,000 lb capability, a 5 lb resolution and nailed my personal body weight to within the resolution with no last digit dithering. That indicates to me better than 2.5 lb internal resolution. Calibration of this particular scale is done in the digital world - roll a 50,000 lb calibrated trailer onto the scale, tell the scale processor that it weighs 50,000.0 lbs and it figures out its own conversion factors. HOWEVER. Servicing the thing means working down in the kind of precision levels we're talking about. I have the 4 lightning-struck load cells and the matched summing box in my shop ($10,000 from the scale company) so when I get time I can see how they do it that precise with so few parts and with the load cells and summing box out in the weather. There are only 4 wires coming from each load cell so the temperature compensation has to be built into the mechano-electrical design and not externally compensated. John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN In theory, there is no difference between theory and practice. In practice, there is. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Voltage Standards
On Sat, 29 Nov 2008 03:32:23 -0600, Brian Kirby <[EMAIL PROTECTED]> wrote: >Maybe we should consider coming up with a standard voltage reference as >a TAPR project. We have a lot of good brainpower out here and it seems >a lot of experience available. I think that this is a spectacular idea. Actually, two standards would be nice. One low-ppm one for us "volt-nuts" (maybe this list ought to change names to "standards-nuts" or "precision-nuts") and another good enough to check 3.5 and 4.5 digit meters. With all the cheap-spit Chicom DVMs on the market, some of which don't even make a good SWAG, a cheap standard that any ham or other nerd could afford would go a long way toward eliminating a LOT of headaches for folks like us. I answer numerous tech questions every day and one of the first questions I've learned to ask when voltage measurements are involved is "what kind of DVM are you using?" If it's a sub $50 chicom special, I suggest that they buy a better meter before we waste time working on the "problem". Awhile back I bought several ChiCom DVMs from a flea market vendor for $5 a pop, thinking I could toss one in each car for on-the-side-of-the-road troubleshooting. Problem is, the damned thing varies over half a volt on the 20 volt scale between a new 9 volt battery and one that just lights the low battery indicator. They're using a standard DVM chip so they had to actually WORK at it to make it that bad!!! One day when I have a few spare round tuits I'm going to open one up and see what's going on. Bet I find a simple resistor divider instead of the voltage reference or something like that. Anyway, here's my vote for a TAPR Volt! John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN WARNING: Do not use this hair dryer in the shower! ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Voltage standards
On Sun, 30 Nov 2008 17:27:54 -0700 (MST), "M. Warner Losh" <[EMAIL PROTECTED]> wrote: >The thing that got me was the word 'really' in Bruce's statement. It >read like someone who had tried it, had limited success, but in the >end wound up believing that while possible, it wasn't really >practical. After thinking that, I couldn't imagine that somebody on >the list hadn't tried it for some reason or another over the years. Well, before my fire I had a gamma spectrometer based on an LN2 cooled HpGe crystal in my basement lab. Right beside it was a similarly cooled SiLi detector for alpha and X-ray spectroscopy. What can I say? I'm a nuke. that's what we do. I managed to save the Canberra MCA, though it's grossly obsolete now, there being little USB dongles that do the job these days. I have been coveting one of the later model HpGe detectors with the Sterling refrigeration pump. No more LN2 deliveries. Kinda pricey on a retiree's budget. One of those things that I've always wanted to do was to lash together a liquid air plant from, say, refrigeration parts. Never had the time and the funds at the same time. John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN You can't turn [MS] shovelware into reliable software by patching it a whole lot. -Marcus Ranum ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] US Shipping Was huntron tracker advice
On Thu, 27 Nov 2008 21:55:26 +1300, "Steve Rooke" <[EMAIL PROTECTED]> wrote: >Hmmm... International Traffic in Arms Regulations, well I don't like >to poke holes in that excuse but unless the US customs are REALLY >paranoid, I can't see how most of the items I have tried to purchase >would be covered under this. But, I suppose you could poke someone in >the eye with a ball-point pen therefore it could be labled an an arm >but I'm sure there are other reasons for most of refusals to ship >outside the 48 States. It's not just a couple of dealers who take this >position, it seems to be the case with a number of sellers sadly. It is more than just the ITAR hassles. There are hassles all around. either you lie at the post office about the value or you pay customs there. The paperwork takes time. There is no legal recourse in the case of fraud. Just not worth the effort for most folks when they can sell their stuff here. > >What I need is a magic wormhole that runs from a US address and ends >up in my home. Anyone got a design for one of these, sort of like a >stargate :-) Don't know about wormholes but there are people who do that, take receipt of something you purchased and ship it to you. I used to do that when I lived next door to the post office. I charged a small fee to cover my labors and to average out the PO fees other than postage. Alas, the closest PO to me now is about 40 miles. Bet you could find other people to do that for you. If you're dealing on sleazebay, why not put up a Wormhole for sale. Describe the services and let people make offers. Sleazebay may pull it after a few days but I bet you'd find someone. John -- John De Armond See my website for my current email address http://www.neon-john.com http://www.johndearmond.com <-- best little blog on the net! Tellico Plains, Occupied TN I'm going crazy. Wanna come along? ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPS signal simulator
>In my quest to keep improving my GPSDO, a simple test tool > that I find indispensable is a GPS 1PPS (or 100Hz) signal simulator > reference. Others may also find this useful because it allows testing the > PLL & DO in their GPSDO to Cs type accuracy using a standard OCXO. Warren, There's been some discussion about a GPS simulator for the purpose of playing with GPSDO algorithms a couple of times on the list over the years. But since you're making more progress than most have, here is a nice pair of 400,000 (!) sample data sets for you to use: http://www.leapsecond.com/pages/gpsdo-sim/ For playing with GPSDO, the character of the typical 1PPS is very easy to model (it's basically a few ns of noise that nicely averages down at 1 over tau out past a day) so going all the way back to RF simulation of the GPS SV signal(s) might be overkill. In any event, I found it much easier to just take real GPS 1PPS data, and real OCXO data, and then simulate a GPSDO from those two raw data sets. You can plot phase, frequency, ADEV of both inputs and one output and see the GPSDO humps we always talk about, etc. /tvb ** Tom Thanks that should be very useful for software simulations. The use I had in mind for the tool I described where for the next stage of testing. It can be used to test at the REAL Hardware level, using a 'perfect' GPS signal with no noise or with any type of desired controlled noise. For example it is hard and time consuming to see how many ps of error your phase detector is adding or what the phase margin or noise gain is of the H/W PLL. Is the power supply good enough or is it causing errors, etc When using real GPS data, the random noise will hide the advanced type of information you may want to take. The other use of the Hardware simulator is for someone that wants to know how accurate their GPSDO is but does not have access to a source accurate enough to test their GPSDO. WarrenS ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
