[time-nuts] Crude Survey Technique

Fri Nov 22 22:12:41 UTC 2013

On the transite, I thought that might be an issue. You really need a
Theodolite. You can probably pick up a used Wild T-2 or Kern DKM-2 for not
a lot on eBay. A T-3 is o0verkill.

Asian Total Stations have pretty much killed the commercial marked for
manual survey instruments. The ones w/ inverting telescopes tend to be
cheaper.

-John

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

>
>  Hello and thanks to all for the great ideas.
>
>
> Re: [time-nuts] Crude Survey Technique
>
>
>
>  Some interim comments:
>
> *agree with regard to using pole star. However it is below freezing here
> and so I won't be out in the dark with my camera. A good verification
> technique that must await warmer weather!!
>
> *thanks for the suggestion re. the transit. Unfortunately the elevation
> measurement only goes to 30 degrees and I am at 38.7 degrees latitude. I
> should have bought the one with more elevation range and a built in
> precision compass. Still might do that.
>
> *I have a Stocker and Yale Army compass - nice thing but 2 degrees is
> probabily beyond its capability except as a sanity check
>
> *Forced my T-bolt to find itself 9 times in the last 24 hours:
> Average Longitude : -94.70983
> Extreme Spread :000090 degrees
> Standard Devation : 2.58 e-5 degrees
>
> At my latitude 1 degree is 285,402.9 Ft
> So the error at 1 standard deviation is 7.4 ft.
> Who ever guessed 10 ft has achieved GURU status.
>
> So doing the ATAN at various ranges we get
>
> 200 ft  2.12 degrees
> 400 ft  1.06 degrees
> 600ft  0.71 degrees.
>
> 400 ft is easy and 600 is possible. However the sun shadow method seems an
> equally good approach.
>
> Question - If I use 3 T-bolts on the same antenna, feedline, splitter etc.
> and run 3 instances of T-bolt mon - can the results be improved???
>
> Thanks for all the help   - john k6iql
>
>
>
>
>
>
>
> -----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 1:35 pm
> Subject: time-nuts Digest, Vol 112, Issue 77
>
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> Today's Topics:
>
>    1. Re: Crude Survey Technique (Robert Atkinson)
>    2. Re: DMTD: Mixer DC offset will result in time offset at
>       zero-crossing detector out? (Bruce Griffiths)
>    3. Re: Isolation achieved by opamp based isoamp? (Charles Steinmetz)
>    4. Re: Off-Topic Question -- German Composition Resistors
>       (Didier Juges)
>    5. Re: Thunderbolt Simulator (paul swed)
>    6. Re: Crude Survey Technique (Brian Lloyd)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Fri, 22 Nov 2013 17:06:51 +0000 (GMT)
> From: Robert Atkinson <robert8rpi at yahoo.co.uk>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Crude Survey Technique
> Message-ID:
> 	<1385140011.91089.YahooMailNeo at web171902.mail.ir2.yahoo.com>
> Content-Type: text/plain; charset=iso-8859-1
>
> Hi Jim,
> I disagree, the Medium Landing Compass IS accurate to better than 30
> minutes
> (0.5deg). This is also the smallest graduation so it can be read to better
> than
> 15 minutes. The calibration chart is given to 10 minutes every 15 degrees.
> It
> does of course indicate the orientation of the local magnetic field. To
> ensure
> there is no local distortions you need to do a site survey. This can be
> acheived
> by comparing bearings to a distant object along a baseline or taking
> reciprical
> bearings. CAA CAP562 part 8 leaflet 1
> http://www.helitavia.com/docs/CAP562_2007_08.pdf?
>
> has lots of good info.
>
> (full version here http://www.caa.co.uk/docs/33/CAP562RFS.pdf? large file
> over
> 10MB)
>
> Robert G8RPI (CEng, licenced aircraft engineer for 30 years, I've done
> many
> aircraft swings)?
>
>
>
> ________________________________
>  From: Jim Lux <jimlux at earthlink.net>
> To: time-nuts at febo.com
> Sent: Friday, 22 November 2013, 14:25
> Subject: Re: [time-nuts] Crude Survey Technique
>
>
> On 11/21/13 11:32 PM, Robert Atkinson wrote:
>> I'd also go for a compass if you want magnetic north, but then I have a
>> good
> one, a "medium landing compass". Mine dates from WWII but they are still
> made
> http://www.sirs.co.uk/ground/landing_compasses/patt2/landing_resource
>> These are used to align the standbay and remote reading compasses on
>> aircraft.
> Good to half a degree. If you need better ther is the Watts Datum Compass.
>>
>> Robert G8RPI.
>
> That compass is *precise* to 1/2 degree, but not *accurate* to 1/2
> degree. It comes with a calibration card, and is presumably used in a
> place with a uniform field (e.g. for calibrating an aircraft compass,
> which is done in an open area with no known magnetic anomalies).? If
> you're in a different environment, the card values may be incorrect.
>
> It is essentially as "comparison standard".? You put it next to the
> aircraft and move both in a systematic pattern and you use it to
> "calibrate out" the variations in the plane's internal compass.
>
> However you're going to be subject to the local magnetic field anomalies
> (and they're surprisingly large).
>
> http://minerals.usgs.gov/news/newsletter/v1n2/3aeromag.html
>
> On the 1km scale maps in the USGS reports, you can see magnetic
> anomalies of 500 nT.? Earth's field is about 30-60 microTesla, so these
> anomalies are in the "one part in 100" kind of range.? It is true that
> the gradient is fairly small: It is unlikely you have an anomaly of 500
> nT and your neighbor has -200 nT. But it's obvious that the magnetic
> variation (angle between true and indicated magnetic north) isn't the
> nice smooth surface implied by the map of variation you get with the
> compass.
>
> http://dspace.sunyconnect.suny.edu/bitstream/handle/1951/47859/Winslow_MS.pdf;jsessionid=7D7A116045A54816C9DCF963AF3D2580?sequence=1
>
> is a short paper that talks about gradients in a small scale anomaly of
> 0.22 nT/meter? (and I get the impression that that is big).
>
> There's also other locally produced magnetic fields you'd have to worry
> about.
>
> I gave an E&M class a problem to figure out if you could tell whether
> you could use a hand compass to tell if the Pacific Intertie 1MV HVDC
> link (3000 A) was operating bipolar or unipolar. (at 50 meters, the
> field from one wire is about 6 microTesla, so yes, you can detect it)
>
>
> http://msi.nga.mil/MSISiteContent/StaticFiles/HoMCA.pdf
> is all about calibrating a ship's compass
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> ------------------------------
>
> Message: 2
> Date: Sat, 23 Nov 2013 06:29:01 +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: <528F945D.80902 at xtra.co.nz>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Stephan Sandenbergh wrote:
>> 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)?
>>
>>
> 1st section is common mode  low pass filter, 2nd section is differential
> common mode low pass filter.
>
> Bruce
>
>> 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?
>>>>
>>>>
>>>> _______________________________________________
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>>>> 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
>>> _______________________________________________
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>> _______________________________________________
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>
>
>
> ------------------------------
>
> Message: 3
> Date: Fri, 22 Nov 2013 12:33:43 -0500
> From: Charles Steinmetz <csteinmetz at yandex.com>
> 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: <20131122214450.in9mIASU at smtp14.mail.yandex.net>
> Content-Type: text/plain; charset="us-ascii"; format=flowed
>
> Stephan wrote:
>
>>The discrete transistor type amplifiers achieve around 120dB or more
>>at 10MHz.
>
> Well, SOME discrete transistor amplifiers CAN achieve 120dB or more
> of reverse isolation, if everything is done properly.  But 120dB or
> more takes careful attention to detail at every step -- it is very
> far from automatic.
>
> Best regards,
>
> Charles
>
>
>
>
>
> ------------------------------
>
> Message: 4
> Date: Fri, 22 Nov 2013 13:34:00 -0600
> From: Didier Juges <shalimr9 at gmail.com>
> To: Robert Atkinson <robert8rpi at yahoo.co.uk>, 	Discussion of precise
> 	time and frequency measurement <time-nuts at febo.com>
> Subject: Re: [time-nuts] Off-Topic Question -- German Composition
> 	Resistors
> Message-ID:
> 	<CAMQqFu=TcLbDGD5t8WgPEUiyRfjVOG6-TCSd5pdPsx+-VT-7bg at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Must have been Allen Bradley :)
> Same problem here with military equipment!
>
>
> On Thu, Nov 21, 2013 at 4:17 PM, Robert Atkinson
> <robert8rpi at yahoo.co.uk>wrote:
>
>> May be a bit of drift and reading back to front. Some years ago we
>> bought
>> a quantity of moulded carbon compostion resistors from a top US
>> manufacturer. A sample check showed that none of them met the 10%
>> tolerance. The maufacturer said "bake them for a day two"! The resistors
>> then passed. Why not replace them with modert types you ask? Type
>> approved
>> equipment with the original designers long gone and the current type
>> certificate holder unwilling or unable to approve the change. Welcome to
>> the world of aviation where we are still supporting equipment designed
>> 50
>> or more years ago.
>>
>> Robert G8RPI.
>>
>>
>>
>>
>> ________________________________
>>  From: Adrian <rfnuts at arcor.de>
>> To: Discussion of precise time and frequency measurement <
>> time-nuts at febo.com>
>> Sent: Thursday, 21 November 2013, 20:53
>> Subject: Re: [time-nuts] Off-Topic Question -- German Composition
>> Resistors
>>
>>
>> Hi Bruce,
>> no. Same color code here.
>> However, certain carbon composition resistors from the 60's/70's are
>> notoriously unreliable. The common effect is drift to significantly
>> higher values. Besides that, they can get pretty noisy.
>> Adrian
>>
>> Brucekareen at aol.com schrieb:
>> > While tracing out a PC board from an instrument manufactured in
>> Germany,
>> I
>> > quickly discovered the color code on 1/4-watt composition resistors is
>> not
>> > the same as that commonly used in the US  For example, I would measure
>> > about 10,000-ohms across a presumably good resistor that appeared to
>> be
>> marked
>> > 2700-ohms.  Has/does Germany used a different code for such parts?
>> >
>> > Bruce, KG6OJI
>> > _______________________________________________
>> > time-nuts mailing list -- time-nuts at febo.com
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>>
>> >
>>
>> _______________________________________________
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>
> ------------------------------
>
> Message: 5
> Date: Fri, 22 Nov 2013 14:28:04 -0500
> From: paul swed <paulswedb at gmail.com>
> To: Discussion of precise time and frequency measurement
> 	<time-nuts at febo.com>
> Subject: Re: [time-nuts] Thunderbolt Simulator
> Message-ID:
> 	<CAD2JfAgrHU_XpT2W=TSvmFTF6D_gRTejEA47+yLfu-YXwG26tA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Link is good
> Thanks again
>
>
> On Fri, Oct 25, 2013 at 3:32 PM, Didier Juges <shalimr9 at gmail.com> wrote:
>
>> In order to test my upcoming Thunderbolt Monitor, I developed a small
>> piece
>> of software to allow me to generate controlled Primary and Supplemental
>> timing packets per the Trimble spec.
>> I think the result may be useful to those who own Trimble Tunderbolt
>> monitoring tools, so I decided to make it available.
>> It is very much beta at this point, but during my testing, I could not
>> make
>> it fail when talking to the Trimble Thunderbolt Monitor software.
>> You can download it from
>> http://www.ko4bb.com/Timing/GPSMonitor/TBoltSim.php
>>
>> Let me know how it goes via direct message, no need to bog the list down
>> with this.
>>
>> Didier KO4BB
>> _______________________________________________
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>
>
> ------------------------------
>
> Message: 6
> Date: Fri, 22 Nov 2013 11:19:51 -0600
> From: Brian Lloyd <brian at lloyd.com>
> To: "jfor at quikus.com" <jfor at quikus.com>, 	Discussion of precise time
> 	and frequency measurement <time-nuts at febo.com>
> Subject: Re: [time-nuts] Crude Survey Technique
> Message-ID:
> 	<CAE3hgTdk3+g-hjik8EkgSf6TuXxtVqHxUF3zKzGrNZ_HFi=vfA at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> On Friday, November 22, 2013, J. Forster wrote:
>
>> If the telescope on your transit can go to your lattitude, sight Polaris
>> and you're done after a simple calculation.
>
>
> This is the simplest high-accuracy solution. Celestial navigation is your
> friend.
>
> A magnetic compass is the simplest solution. Magnetic variation is found
> on
> all VFR aviation navigation charts.
>
> 2 degrees is an interesting number. It seems either too accurate or not
> accurate enough for most applications I can think of.
>
> <https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts>
>
>
>
> --
> Brian Lloyd, WB6RQN/J79BPL
> 706 Flightline Drive
> Spring Branch, TX 78070
> brian at lloyd.com
> +1.916.877.5067
>
>
> ------------------------------
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> End of time-nuts Digest, Vol 112, Issue 77
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