Hi A lot depends on exactly how old the TBolt is. If it's a unit from 2000 it's a different beast than one from 2005.
Bob On Jan 14, 2010, at 7:19 PM, Mitchell Janoff wrote: > My z3816a no longer locks to GPS. While it still outputs 1 PPS and 10MHz, it > doesn't track any satellites. I've checked the GPS card and it locks outside > the unit, so I don't think that's the problem. I've decided to replace it > and was wondering if I should get another z3816a or T-Bolt. They would both > be about the same price, and they are both guaranteed working. I use them > primarily as the reference standard for all my equipment, and as a time > standard for my house. Based on all the activity and discussions regarding > the T-Bolt, I'm wondering if this is a better option. > > Thanks in advance. > > Mitch. > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of [email protected] > Sent: Thursday, January 14, 2010 3:55 PM > To: [email protected] > Subject: time-nuts Digest, Vol 66, Issue 69 > > Send time-nuts mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of time-nuts digest..." > > > Today's Topics: > > 1. Re: I like Nixie tubes!! (Peter Putnam) > 2. Re: I like Nixie tubes!! (Pete Lancashire) > 3. Re: Accurate Position (gonzo .) > 4. Re: Accurate Position (Rob Kimberley) > 5. Re: GPSDO Design (Bruce Griffiths) > 6. Weird T-Bolt elevation readings... (Michael Baker) > 7. Re: GPSDO Design (Bruce Griffiths) > 8. Re: Weird T-Bolt elevation readings... (Didier Juges) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Thu, 14 Jan 2010 10:46:24 -0800 > From: Peter Putnam <[email protected]> > Subject: Re: [time-nuts] I like Nixie tubes!! > To: Discussion of precise time and frequency measurement > <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Greetings, > > If anybody needs a few of the proprietary hp 1820-0092 Nixie driver > chips, please contact me off list. > > Regards, > Peter > > > > > > > ------------------------------ > > Message: 2 > Date: Thu, 14 Jan 2010 11:00:41 -0800 > From: Pete Lancashire <[email protected]> > Subject: Re: [time-nuts] I like Nixie tubes!! > To: [email protected], Discussion of precise time and frequency > measurement <[email protected]> > Message-ID: > <[email protected]> > Content-Type: text/plain; charset=ISO-8859-1 > > Hi Pete, it would be nice to have a couple, I've got a couple old HP's 5261A > that use them and I know of at least on bad > chip. A typical useless counter but like most I just can't get rid of it. > Would be fun to convert one to a clock ! > > what r u asking ? > > -pete > > > On Thu, Jan 14, 2010 at 10:46 AM, Peter Putnam > <[email protected]>wrote: > >> Greetings, >> >> If anybody needs a few of the proprietary hp 1820-0092 Nixie driver chips, >> please contact me off list. >> >> Regards, >> Peter >> >> >> >> >> _______________________________________________ >> 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. >> > > > ------------------------------ > > Message: 3 > Date: Thu, 14 Jan 2010 19:22:54 +0000 > From: "gonzo ." <[email protected]> > Subject: Re: [time-nuts] Accurate Position > To: time-nuts <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset="iso-8859-1" > > > Hi Dan, > you should be aware that Google Earth does not give an "accurate" location. > It give a "precise" location, but not particularly accurate (a distinction > particularly relevant to this forum). > > ian > > >> Date: Thu, 14 Jan 2010 09:18:40 -0800 >> From: Dan Rae <[email protected]> >> Subject: [time-nuts] Accurate Position >> To: Discussion of precise time and frequency measurement >> <[email protected]> >> Message-ID: <[email protected]> >> Content-Type: text/plain; charset=ISO-8859-1; format=flowed >> >> I just found out that Google Earth now gives a seemingly quite accurate >> position at the mouse pointer which I don't remember seeing before. >> >> This would seem like a good way to start for a T-bolt survey for example. >> >> Dan > > > _________________________________________________________________ > Time for a new car? Sell your old one fast! > http://clk.atdmt.com/NMN/go/157637060/direct/01/ > > ------------------------------ > > Message: 4 > Date: Thu, 14 Jan 2010 19:25:39 -0000 > From: "Rob Kimberley" <[email protected]> > Subject: Re: [time-nuts] Accurate Position > To: <[email protected]>, "'Discussion of precise time and frequency > measurement'" <[email protected]> > Message-ID: <201eb3559a0943579518244f66433...@robinhp> > Content-Type: text/plain; charset="us-ascii" > > Sounds good. > > Remember it's the position of the antenna.... > > Rob K > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf Of Dan Rae > Sent: 14 January 2010 5:19 PM > To: Discussion of precise time and frequency measurement > Subject: [time-nuts] Accurate Position > > I just found out that Google Earth now gives a seemingly quite accurate > position at the mouse pointer which I don't remember seeing before. > > This would seem like a good way to start for a T-bolt survey for example. > > Dan > > > > > _______________________________________________ > 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. > > > > > > ------------------------------ > > Message: 5 > Date: Fri, 15 Jan 2010 08:57:06 +1300 > From: Bruce Griffiths <[email protected]> > Subject: Re: [time-nuts] GPSDO Design > To: Discussion of precise time and frequency measurement > <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > There are 4 principal sources of noise > > 1) The GPS receiver > > 2) The 4046 Phase detector > > 3) The opamp > > 4) The OCXO > > In the short term the GPS receiver noise will dominate. > In the long term the 4046 phase detector noise and drift together with > the OCXO noise and drift will dominate. > > Unless you make an extremely poor choice of opamp the 4046 phase > detector noise and drift will be much larger than that of the opamp. > > > Bruce > > John Foege wrote: >> Hi All, >> >> Quick question for the more experienced members here with GPSDO >> design/operation. Let's assume I'm using a 4096 phase comparator chip >> followed by some kind of long time constant lowpass loop filter, >> whether it be analog or digital, is not of concern for the following >> question. >> >> Obviously using a 74HCT4096 would mean that my EFC voltage range would >> be approx. 0-5V. If I wanted to use an OCXO with say a 0-8V EFC >> voltage range, then I would be inclined to simply use an op-amp >> amplifier with a gain of 1.6 to scale the EFC voltage accordingly. >> >> But not just any op-amp would do I take it? High-speed would of course >> be of no concern. Also low-offset would be of little concern, as the >> PLL would work to correct this, and it therefore seems to be >> negligible. However, the part that's got me thinking is noise. >> Obviously any noise at the ouput of the amp would adversely affect the >> frequency stability of the OCXO. >> >> I thought the best way to control this would be to use an extremely >> low noise op-amp employing a rather large compensation cap to give me >> a rather small bandwidth, perhaps only a few hundred hertz. >> >> Anyone have experience with this? Assuming I have an OXCO with a max. >> pulling range of 1ppm or 1e-6 over a 10V range, then I effectively can >> pull 1e-7 per volt. This translates to 1e-10 per millivolt and 1e-13 >> per microvolt. Assuming that is a logical conclusion, then for a good >> OCXO, in which I can at best hope for 5e-12 stability for tau=1s (e.g. >> HP10811A), I would strive to to keep the noise at such a level that it >> is an order of magnitude better than the best short term stability >> figure. Accordingly, then I should shoot to keep any noise under 1 >> microvolt? >> >> I don't have much experience with noise calculations. I know it is >> specified in nV/sqrt(Hz) generally. Translating this to something >> practical is basically the assistance I'm looking for here. >> >> I would appreciate anyone being able to teach me a bit more about this. >> >> Thank you in all in advance. >> >> Sincerely, >> >> John Foege >> >> _______________________________________________ >> 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. >> >> > > > > > > ------------------------------ > > Message: 6 > Date: Thu, 14 Jan 2010 15:28:37 -0500 > From: Michael Baker <[email protected]> > Subject: [time-nuts] Weird T-Bolt elevation readings... > To: [email protected] > Message-ID: <[email protected]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > Hello, TimeNutters-- > > While we are on a thread about Trimble T-bolts, > perhaps someone might expand on why my T-bolt > does not ever come up with altitude readings that > are even close. After a long fix, the Lat-Lon > coordinates are pretty close, but the altitude > is always given as around 2 meters. We are pretty > low here in Flori-DUH, but not THAT low. My > ground elevation here is 28M ABMSL and my > GPS antenna is another 8M above that on top > of my fireplace chimney. I have roughly 50 ft > of RG-59 cable on the antenna, but altering the > cable length value does not seem to have any > effect. I get these same very low altitude readings > with TBOLTMON and Lady Heather v3 beta. > > Since I know my altitude well withing one meter, > should I enter that manually? What is the > procedure for doing that? > > Suggestions...?? > > Thanks!! > > Mike Baker > ------------------- > > > > > > ------------------------------ > > Message: 7 > Date: Fri, 15 Jan 2010 09:54:04 +1300 > From: Bruce Griffiths <[email protected]> > Subject: Re: [time-nuts] GPSDO Design > To: Discussion of precise time and frequency measurement > <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=ISO-8859-1; format=flowed > > The time constant for a passive loop filter followed by an amplifier is > > tau = Ko*Kd*A/(2+PI*fn)^2 > > where > Ko is the phase detector gain (radian/volt) > Kd is the VCO gain (rad/sec/volt) > A is the amplifier gain > > For a CMOS exclusive OR phase detector with a 5V supply > > Ko = 0.79 volt/rad > > For a 10811A > > Kd~ 0.63 rad/sec/volt (this value will be different for each OCXO and in > general the EFC curve is nonlinear, the characteristic should be > measured for you particular OCXO ) > > For A =2, > fn = 0.01Hz > > Tau = 250 sec > > With an active filter the time constant (in this case) will be 1/2 this > or 125 sec. > > If you only use a portion (say 10%) of the EFC range then the amplifier > gain is reduced to 0.2 and the time constant (for a passive filter) > required becomes 25 sec. > However more manual tuning of the 10811 may be required every few months > (depends on the 10811A drift) to recentre the EFC voltage. > > If the phase comparison is made at 100Hz then the delay of a typical > HCMOS synchronous divider (used to divide a 10MHz OCXO down to 100Hz) > will be around 20ns with a tempco of about 80ps/C. > The typical delay of a cascaded HC7490 style divider may be 10x this > with a tempco of around 800ps/C. > > A change in EFC voltage of 100uV will alter the OCXO frequency by 1 part > in 1E12, this corresponds to a change in amplifier input bias current of > 100pA (for a 1 megohm filter resistor) or an input offset voltage change > of 100uV. As the filter time constant increases the required resistor > value (for obtainable/affordable capacitors) will increase. > > Thus the stability of the amplifier bias current and the capacitor > leakage become critical for longer time constants. > > A zero drift amplifier like the LTC1151 may be worth considering as long > as any (~1000Hz for the LTC1151 ) chopper related noise is filtered out > with a passive low pass filter at the amplifier output. > > Bruce > > > > Bruce Griffiths wrote: >> There are 4 principal sources of noise >> >> 1) The GPS receiver >> >> 2) The 4046 Phase detector >> >> 3) The opamp >> >> 4) The OCXO >> >> In the short term the GPS receiver noise will dominate. >> In the long term the 4046 phase detector noise and drift together with >> the OCXO noise and drift will dominate. >> >> Unless you make an extremely poor choice of opamp the 4046 phase >> detector noise and drift will be much larger than that of the opamp. >> >> >> Bruce >> >> John Foege wrote: >>> Hi All, >>> >>> Quick question for the more experienced members here with GPSDO >>> design/operation. Let's assume I'm using a 4096 phase comparator chip >>> followed by some kind of long time constant lowpass loop filter, >>> whether it be analog or digital, is not of concern for the following >>> question. >>> >>> Obviously using a 74HCT4096 would mean that my EFC voltage range would >>> be approx. 0-5V. If I wanted to use an OCXO with say a 0-8V EFC >>> voltage range, then I would be inclined to simply use an op-amp >>> amplifier with a gain of 1.6 to scale the EFC voltage accordingly. >>> >>> But not just any op-amp would do I take it? High-speed would of course >>> be of no concern. Also low-offset would be of little concern, as the >>> PLL would work to correct this, and it therefore seems to be >>> negligible. However, the part that's got me thinking is noise. >>> Obviously any noise at the ouput of the amp would adversely affect the >>> frequency stability of the OCXO. >>> >>> I thought the best way to control this would be to use an extremely >>> low noise op-amp employing a rather large compensation cap to give me >>> a rather small bandwidth, perhaps only a few hundred hertz. >>> >>> Anyone have experience with this? Assuming I have an OXCO with a max. >>> pulling range of 1ppm or 1e-6 over a 10V range, then I effectively can >>> pull 1e-7 per volt. This translates to 1e-10 per millivolt and 1e-13 >>> per microvolt. Assuming that is a logical conclusion, then for a good >>> OCXO, in which I can at best hope for 5e-12 stability for tau=1s (e.g. >>> HP10811A), I would strive to to keep the noise at such a level that it >>> is an order of magnitude better than the best short term stability >>> figure. Accordingly, then I should shoot to keep any noise under 1 >>> microvolt? >>> >>> I don't have much experience with noise calculations. I know it is >>> specified in nV/sqrt(Hz) generally. Translating this to something >>> practical is basically the assistance I'm looking for here. >>> >>> I would appreciate anyone being able to teach me a bit more about this. >>> >>> Thank you in all in advance. >>> >>> Sincerely, >>> >>> John Foege >>> >>> _______________________________________________ >>> 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. >>> >> >> >> >> _______________________________________________ >> 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. >> > > > > > > ------------------------------ > > Message: 8 > Date: Thu, 14 Jan 2010 20:54:53 +0000 > From: "Didier Juges" <[email protected]> > Subject: Re: [time-nuts] Weird T-Bolt elevation readings... > To: "Time-Nuts" <[email protected]> > Message-ID: > > <1142861739-1263502495-cardhu_decombobulator_blackberry.rim.net-7227962...@b > da224.bisx.prod.on.blackberry> > > Content-Type: text/plain > > To tell you how far above ground you are, the GPS has to know where the > ground is. For that, it is using a model that is not perfect. That is why > John Miles' GPS tells him he should get his scuba gear immediately... > > If you google "geoid" you will find more than you wanted to know about it. > > Didier > > ------Original Message------ > From: Michael Baker > Sender: [email protected] > To: Time-Nuts > ReplyTo: Time-Nuts > Subject: [time-nuts] Weird T-Bolt elevation readings... > Sent: Jan 14, 2010 2:28 PM > > Hello, TimeNutters-- > > While we are on a thread about Trimble T-bolts, > perhaps someone might expand on why my T-bolt > does not ever come up with altitude readings that > are even close. After a long fix, the Lat-Lon > coordinates are pretty close, but the altitude > is always given as around 2 meters. We are pretty > low here in Flori-DUH, but not THAT low. My > ground elevation here is 28M ABMSL and my > GPS antenna is another 8M above that on top > of my fireplace chimney. I have roughly 50 ft > of RG-59 cable on the antenna, but altering the > cable length value does not seem to have any > effect. I get these same very low altitude readings > with TBOLTMON and Lady Heather v3 beta. > > Since I know my altitude well withing one meter, > should I enter that manually? What is the > procedure for doing that? > > Suggestions...?? > > Thanks!! > > Mike Baker > ------------------- > > > > _______________________________________________ > 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. > > > ------------------------ Sent from my BlackBerry Wireless thingy while I do > other things... > > ------------------------------ > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > End of time-nuts Digest, Vol 66, Issue 69 > ***************************************** > > > _______________________________________________ > 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. > _______________________________________________ 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.
