[time-nuts] T-bolt vs z3816a
Mitchell Janoff
majanoff at verizon.net
Fri Jan 15 00:19:22 UTC 2010
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
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------------------------------
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
-------------------
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To unsubscribe, go to
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------------------------ Sent from my BlackBerry Wireless thingy while I do
other things...
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