[time-nuts] Crude Survey Technique

Fri Nov 22 16:47:21 UTC 2013

If the telescope on your transit can go to your lattitude, sight Polaris
and you're done after a simple calculation.

-John

====================

>
>  Stephen -
>
>
>  [time-nuts] Crude Survey Technique
>
>
>
>  Thanks for describing your method. I am learning a lot. here is agovt web
> site that will give the compass correction for any long and lat. Here in
> KS the magnetic pole is about 2.3 degrees to the east.
>
> Once all the ideas are in, I will put together a summary.
>
> I have a number of the required tools, compass, several T-bolts,
> surveyor's transit, tall poles, laser level, and bulls-eye levels.
> So with all of these good ideas I am sure I will get it right. It will be
> interesting to cross check the various methods.
>
> It also occurred to me that I could buy a 3 ft length of hardened steel
> shafting, wrap a couple of dozen turns of # 6 around it and then connect
> it to a big lead acid battery via a 200 Amp fuse. Should result in a 3 ft
> long compass needle. You only get to use the fuse once though!
>
> Thanks to all  -john
>
>
>
> -----Original Message-----
> From: time-nuts-request <time-nuts-request at febo.com>
> To: time-nuts <time-nuts at febo.com>
> Sent: Fri, Nov 22, 2013 6:29 am
> Subject: time-nuts Digest, Vol 112, Issue 75
>
>
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> Today's Topics:
>
>    1. Re: Motorola M12+ (Azelio Boriani)
>    2. Re: Isolation achieved by opamp based isoamp? (Bruce Griffiths)
>    3. Re: DMTD: Mixer DC offset will result in time offset at
>       zero-crossing detector out? (Bruce Griffiths)
>    4. Re: Crude Survey Technique (Stephan Sandenbergh)
>    5. Re: Strange 100ns jumps on Motorola M12+T (Bob Camp)
>    6. Re: DMTD: Mixer DC offset will result in time offset at
>       zero-crossing detector out? (Stephan Sandenbergh)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 22 Nov 2013 11:45:17 +0100
> From: Azelio Boriani <azelio.boriani at screen.it>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Motorola M12+
> Message-ID:
> 	<CAL8XPmPPU6e2g90veAFKzMDqVPMsE+qL+Uxr6+RcVHUueyd_Zg at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Strange item... it has an M12+ and a supporting board full of
> components. Protocol translation from 12-channel to 8-channel? The
> link to the PDF file returns a 404.
>
> On Fri, Nov 22, 2013 at 9:32 AM, Pascual Arbona Lopez
> <p.arbona at securimar.com> wrote:
>> I am wondering if this is a sustitute of  the original oncore VP
>> receiver for
> the Z3801 -Z3805. (E-pay 281161070304 )
>> _______________________________________________
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>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 23 Nov 2013 00:18:50 +1300
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Isolation achieved by opamp based isoamp?
> Message-ID: <528F3D9A.5090903 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Stephan Sandenbergh wrote:
>> Something that would be interesting to know is if certain opamps are
>> better
>> suited toward S12 isolation than others. I guess at the expense of noise
>> floor and 1/f corner one could cascade two opamps to improve the S12
>> isolation further.
>>
>>
> The flicker noise corner of an opamp may be lower than you think.
> Current feedback opamps may have higher flicker noise corners than volt
> feedback opamps
>> As soon as you are looking at frequencies of 100MHz you are probably
>> left
>> with the discrete options in any way.
>>
> There are 1GHz and 10GHz opamps available.
>
> Bruce
>>
>> On 22 November 2013 11:45, Stephan
>> Sandenbergh<ssandenbergh at gmail.com>wrote:
>>
>>
>>> Thanks for the spec. I suspected that it would be in that ball park.
>>>
>>> The discrete transistor type amplifiers achieve around 120dB or more at
>>> 10MHz. But, they are a lot more effort to implement than the opamp
>>> designs.
>>>
>>> I believe the transformer in this case is for ground loop isolation
>>> rather
>>> than S12 isolation.
>>>
>>>
>>> On 21 November 2013 20:20, Charles
>>> Steinmetz<csteinmetz at yandex.com>wrote:
>>>
>>>
>>>> Corby wrote:
>>>>
>>>>   This opamp buffer has 80-90db isolation.
>>>>
>>>>>
>>>> That is typical at 5 to 10 MHz *if* (i) all of the splitting is done
>>>> on
>>>> the input side (i.e., each output has its own op amp), and (ii) the
>>>> splitter and all of the construction (grounds, shielding, etc.) is
>>>> done
>>>> correctly.
>>>>
>>>> If any splitting is done on the output side of the op amp(s), by using
>>>> one op amp to drive more than one output through separate back
>>>> terminating
>>>> resistors, the outputs that share an op amp will only be isolated by
>>>> 30 to
>>>> maybe 40 dB (again, assuming that the op amp has been well chosen and
>>>> all
>>>> of the construction is done correctly).
>>>>
>>>> Best regards,
>>>>
>>>> Charles
>>>>
>>>>
>>>>
>>>>
>>>> _______________________________________________
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>>>>
>>>
>>>
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>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 23 Nov 2013 00:15:15 +1300
> From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] DMTD: Mixer DC offset will result in time
> 	offset at zero-crossing detector out?
> Message-ID: <528F3CC3.9010802 at xtra.co.nz>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> Stephan Sandenbergh wrote:
>> Hi,
>>
>> I'm playing with dual-mixer time difference stuff again.  And, came
>> across
>> this and I find it somewhat puzzling since no one else seems to have
>> encountered it. Possibly because I'm missing something?
>>
>> The doubly balanced mixers (of the type known to be used in DMTDs and
>> phase
>> noise measurement systems) are known to have DC offsets. So much so that
>> the guys doing phase noise measurements employ elaborate DC removal
>> circuits in their preamps to combat this.
>>
>> Here's my question: why isn't this DC offset removed in any DMTD
>> circuits
>> I've seen? It seems standard practice to attach the filtered mixer
>> output
>> directly to the zero crossing detector.
>>
>> I did a quick simulation (see attached):
>>
>> The mixer beat is a 10Hz sine 0.7Vpp. If you then use a Collins style
>> zero
>> crossing detector the first stage will have a small gain (I chose a gain
>> of
>> 2.83 from Bruce Griffiths pages (
>> http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)). I then compare
>> this ideal signal to that of a similar one that is offset by 40mV.
>> Notice
>> the asymmetry in the signal due to offset.
>>
>> 40mV result in 1.8ms offset
>> 4mV result in 180us offset
>>
>> Obviously, once the time offset is there no amount of subsequent slope
>> amplification will remove it.
>>
>> I've tested this in practice and bingo, I now have a very accurate way
>> of
>> plotting relative mixer DC offset over time.
>>
>> Any comments?
>>
>>
>>
>> _______________________________________________
>> 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.
> One can always add AC coupling to eliminate this effect as in
> http://www.wriley.com/A%20Small%20DMTD%20System.pdf
>
> Bruce
>
>
> ------------------------------
>
> Message: 4
> Date: Fri, 22 Nov 2013 13:31:04 +0200
> From: Stephan Sandenbergh <ssandenbergh at gmail.com>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Crude Survey Technique
> Message-ID:
> 	<CADbj3vY8unLvjeE77Kh=T3pO5bGyUK=REjXeLEoRM-P+=425mw at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> John,
>
> We had a similar problem when we're trying to setup various antennas at
> various locations pointing at different true North bearings. It turned out
> quite hard to find true North.
>
> We found single carrier GPS surveyed points to be inaccurate to produce
> good bearings across such a short base line. Also, you'll end up with two
> points with some bearing w.r.t. North. Now the problem is that of finding
> a
> third point to give you your N-S base line.
>
> In the end we used a tripod, calibrated gun sight and a turn table with
> degrees markings (those that the photonics people use). If you'd like to
> use this method, you survey a single point on your property (preferably on
> the base line your interested in). Also survey a land mark, like a radio
> mast a few km's away. The further away (the longer the base line) the less
> accurate your surveyed points need to be. Now calculate the North
> bearing of this base line using these two points. Now back at your
> property
> at the surveyed point, point your cross hair at the radio mast and set the
> number of degrees on the turn table to that you have calculated. Fix the
> turn table. 0 degrees should now be true North, and you could now use the
> cross hair to survey the other point.
>
> The tripod should be levelled very carefully, since errors here will put
> you in a different plane and you will end up calculating vector components
> in that plane.
>
>
>
> On 21 November 2013 20:52, <johncroos at aol.com> wrote:
>
>>  I wish to establish a north south line on my property to an accuracy of
>> +/- 2 degrees.
>> Could this be done by loading a T-bolt, Antenna, Power source, and
>> laptop
>> into my
>> little red wagon? The idea being to find two positions several hundred
>> ft
>> apart where either LH or T-bolt Mon report the same latitude? Will
>> either
>> of these programs report to sufficient accuracy? The base line would be
>> 300
>> ft, though more is possible.I realizes that the T-bolt is not a survey
>> device, but I can spend several hours fixing each position if required.
>>
>> All comments appreciated.?? -73 john k6iql
>>
>>
>>
>>
>> _______________________________________________
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>> and follow the instructions there.
>>
>
>
> ------------------------------
>
> Message: 5
> Date: Fri, 22 Nov 2013 07:06:28 -0500
> From: Bob Camp <lists at rtty.us>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Strange 100ns jumps on Motorola M12+T
> Message-ID: <01D166A8-D93A-4B4D-B195-606A6A0DE906 at rtty.us>
> Content-Type: text/plain; charset=windows-1252
>
> Hi
>
> Something is going wrong somewhere. The question is where.  Three ideas /
> targets here:
>
> The counter is a 100 ns (10 MHz input) beast, so it *might* be the issue.
>
> The offset source or the GPS might also be the issue (thus avoiding
> 1/10.24
> MHz).
>
> The idea with the larger offset is that there is no significant accuracy
> degradation with a modest increase in the offset. The exact value isn?t
> the
> issue there, just making it larger. That way you will still properly
> capture
> stuff in the 100 (or more) ns range.
>
> Bob
>
> On Nov 22, 2013, at 4:38 AM, Stephan Sandenbergh <ssandenbergh at gmail.com>
> wrote:
>
>> Hi,
>>
>> Ok, the 53131A trigger settings: I've turned auto trigger off and set it
>> to
>> trigger at 2V (I think this is right, but I'll have to go and double
>> check
>> the exact threshold setting) threshold. Sensitivity is set to high.
>>
>> Location is GPS surveyed and all M12+'s are set to position hold mode.
>>
>> I did record the time stamped GPS data as well so will go have a look at
>> what happened to the constellation at the time of the jumps. Will post
>> when
>> I have results.
>>
>> Sorry if I'm a little slow here, but why is it better to use larger
>> offsets? Also I get that 100ns is exactly one cycle of 10MHz, but why
>> would
>> the 53131A have trouble with this? Surely it uses linear interpolators
>> along with digital counters to calculate the result. Also, I assume the
>> counting doesn't happen at 10MHz, but at a much higher multiple. Had it
>> been done at 10MHz I'd understand that skipping a beat would result in
>> 100ns offset. Granted I don't know much about the innards of the 53131A.
>>
>>
>>
>>
>> On 22 November 2013 02:25, Bob Camp <lists at rtty.us> wrote:
>>
>>> Hi
>>>
>>> To be clear - the idea of going to a non-100 ns multiple is a good one.
>>> You probably should avoid multiples of 1/10.24 MHz as well.
>>>
>>> Bob
>>>
>>> On Nov 21, 2013, at 8:00 AM, Azelio Boriani <azelio.boriani at screen.it>
>>> wrote:
>>>
>>>> Yes, do not use tiny offsets, go to 1us: I use microseconds offsets to
>>>> take PPSes measurements .
>>>>
>>>> On Thu, Nov 21, 2013 at 1:34 PM, Bob Camp <lists at rtty.us> wrote:
>>>>> Hi
>>>>>
>>>>> The counter and offset generator both should be quite accurate at a 1
>>> us offset. That?s large enough that you are outside the range of most
>>> GPS
>>> jumps. If you are going to move things around, you might as well move
>>> out
>>> to that vicinity.
>>>>>
>>>>> Bob
>>>>>
>>>>> On Nov 21, 2013, at 6:20 AM, Tom Van Baak <tvb at LeapSecond.com> wrote:
>>>>>
>>>>>>> Below is a plot so you could see exactly what I measured. What is
>>> peculiar
>>>>>>> is that the time jumps by exactly 100ns to 200ns. Almost as if the
>>>>>>> GPS
>>>>>>> receiver decides to offset the time by twice the amount I set it
>>>>>>> to.
>>> Which
>>>>>>> is why I initially thought it might be a firmware thing. I suppose
>>>>>>> multipath is a good explanation, it is just odd that the time error
>>>>>>> is
>>>>>>> exactly 100ns.
>>>>>>
>>>>>> Hi Stephan,
>>>>>>
>>>>>> A quick test you could perform is set the offset to 125 ns instead
>>>>>> of
>>> 100 ns and see if the jumps still occur, still occur at 100 ns, or now
>>> occur at 125 ns.
>>>>>>
>>>>>> Since you have three M12's offset the third one by 150 ns and see if
>>> it experiences jumps too.
>>>>>>
>>>>>> Question -- are you using the external 10 MHz reference input or
>>> output for any of your 53131A counters?
>>>>>>
>>>>>> /tvb
>>>>>>
>>>>>> _______________________________________________
>>>>>> time-nuts mailing list -- time-nuts at febo.com
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>>>>>
>>>>> _______________________________________________
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>
>
> ------------------------------
>
> Message: 6
> Date: Fri, 22 Nov 2013 14:19:26 +0200
> From: Stephan Sandenbergh <ssandenbergh at gmail.com>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] DMTD: Mixer DC offset will result in time
> 	offset at zero-crossing detector out?
> Message-ID:
> 	<CADbj3vbCUL=MGnsLQadyjmcmpjnEN1JzT=KA=anvnSuJNwNo+g at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> Hi,
>
> Thanks - mystery solved. This is one of the systems that I looked at,
> and missed the DC block in the second amplification stage. I guess it is
> possibly a large Ceramic 10uF. My bad.
>
> Thank you for putting up those web pages I find them to be very good
> references. I spent quite a lot of time reading through them.
>
> Something that puzzles me though is your mixer termination (
> http://www.ko4bb.com/~bruce/LowNoiseMixerPreamp.html). What is the logic
> in
> having the second balun (and connected in that way)?
>
> Regards,
>
> Stephan.
>
>
> On 22 November 2013 13:15, Bruce Griffiths
> <bruce.griffiths at xtra.co.nz>wrote:
>
>> Stephan Sandenbergh wrote:
>>
>>> Hi,
>>>
>>> I'm playing with dual-mixer time difference stuff again.  And, came
>>> across
>>> this and I find it somewhat puzzling since no one else seems to have
>>> encountered it. Possibly because I'm missing something?
>>>
>>> The doubly balanced mixers (of the type known to be used in DMTDs and
>>> phase
>>> noise measurement systems) are known to have DC offsets. So much so
>>> that
>>> the guys doing phase noise measurements employ elaborate DC removal
>>> circuits in their preamps to combat this.
>>>
>>> Here's my question: why isn't this DC offset removed in any DMTD
>>> circuits
>>> I've seen? It seems standard practice to attach the filtered mixer
>>> output
>>> directly to the zero crossing detector.
>>>
>>> I did a quick simulation (see attached):
>>>
>>> The mixer beat is a 10Hz sine 0.7Vpp. If you then use a Collins style
>>> zero
>>> crossing detector the first stage will have a small gain (I chose a
>>> gain
>>> of
>>> 2.83 from Bruce Griffiths pages (
>>> http://www.ko4bb.com/~bruce/ZeroCrossingDetectors.html)). I then
>>> compare
>>> this ideal signal to that of a similar one that is offset by 40mV.
>>> Notice
>>> the asymmetry in the signal due to offset.
>>>
>>> 40mV result in 1.8ms offset
>>> 4mV result in 180us offset
>>>
>>> Obviously, once the time offset is there no amount of subsequent slope
>>> amplification will remove it.
>>>
>>> I've tested this in practice and bingo, I now have a very accurate way
>>> of
>>> plotting relative mixer DC offset over time.
>>>
>>> Any comments?
>>>
>>>
>>> _______________________________________________
>>> 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.
>>>
>> One can always add AC coupling to eliminate this effect as in
>> http://www.wriley.com/A%20Small%20DMTD%20System.pdf
>>
>> Bruce
>> _______________________________________________
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/
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>>
>
>
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