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.
