[time-nuts] T-bolt vs z3816a

Bob Camp lists at cq.nu
Fri Jan 15 02:04:13 UTC 2010


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: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of time-nuts-request at febo.com
> Sent: Thursday, January 14, 2010 3:55 PM
> To: time-nuts at febo.com
> Subject: time-nuts Digest, Vol 66, Issue 69
> 
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> 
> 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 <pico.2008 at sbcglobal.net>
> Subject: Re: [time-nuts] I like Nixie tubes!!
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <4B4F6680.3000007 at sbcglobal.net>
> 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 <pete at petelancashire.com>
> Subject: Re: [time-nuts] I like Nixie tubes!!
> To: peter at ni6e.com, Discussion of precise time and frequency
> 	measurement	<time-nuts at febo.com>
> Message-ID:
> 	<37b6825d1001141100s499f37day73d94e6b6b0651b6 at mail.gmail.com>
> 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
> <pico.2008 at sbcglobal.net>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 -- time-nuts at febo.com
>> 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 ." <cadbloke at hotmail.com>
> Subject: Re: [time-nuts] Accurate Position
> To: time-nuts <time-nuts at febo.com>
> Message-ID: <COL116-W27EFA8CDFADB47DA64860AC66A0 at phx.gbl>
> 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 <danrae at verizon.net>
>> Subject: [time-nuts] Accurate Position
>> To: Discussion of precise time and frequency measurement
>> 	<time-nuts at febo.com>
>> Message-ID: <4B4F51F0.20000 at verizon.net>
>> 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" <rk at timing-consultants.com>
> Subject: Re: [time-nuts] Accurate Position
> To: <danrae at verizon.net>,	"'Discussion of precise time and frequency
> 	measurement'"	<time-nuts at febo.com>
> Message-ID: <201EB3559A0943579518244F66433861 at robinHP>
> Content-Type: text/plain;	charset="us-ascii"
> 
> Sounds good. 
> 
> Remember it's the position of the antenna....
> 
> Rob K 
> 
> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] 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 -- time-nuts at febo.com
> 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 <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] GPSDO Design
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <4B4F7712.2060209 at xtra.co.nz>
> 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 -- time-nuts at febo.com
>> 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 <mpb45 at clanbaker.org>
> Subject: [time-nuts] Weird T-Bolt elevation readings...
> To: time-nuts at febo.com
> Message-ID: <4B4F7E75.3020804 at clanbaker.org>
> 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 <bruce.griffiths at xtra.co.nz>
> Subject: Re: [time-nuts] GPSDO Design
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Message-ID: <4B4F846C.4020902 at xtra.co.nz>
> 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 -- time-nuts at 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 at febo.com
>> 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" <didier at cox.net>
> Subject: Re: [time-nuts] Weird T-Bolt elevation readings...
> To: "Time-Nuts" <time-nuts at febo.com>
> Message-ID:
> 	
> <1142861739-1263502495-cardhu_decombobulator_blackberry.rim.net-722796232- at 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: time-nuts-bounces at febo.com
> 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 -- time-nuts at febo.com
> 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
> time-nuts at febo.com
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> 
> End of time-nuts Digest, Vol 66, Issue 69
> *****************************************
> 
> 
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