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 <[email protected]> > To: time-nuts <[email protected]> > Sent: Fri, Nov 22, 2013 1:35 pm > Subject: time-nuts Digest, Vol 112, Issue 77 > > > 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: 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 <[email protected]> > To: Discussion of precise time and frequency measurement > <[email protected]> > Subject: Re: [time-nuts] Crude Survey Technique > Message-ID: > <[email protected]> > 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 <[email protected]> > To: [email protected] > 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 > _______________________________________________ > 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: 2 > Date: Sat, 23 Nov 2013 06:29:01 +1300 > From: Bruce Griffiths <[email protected]> > To: Discussion of precise time and frequency measurement > <[email protected]> > Subject: Re: [time-nuts] DMTD: Mixer DC offset will result in time > offset at zero-crossing detector out? > Message-ID: <[email protected]> > 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<[email protected]>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 -- [email protected] >>>> 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 -- [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: 3 > Date: Fri, 22 Nov 2013 12:33:43 -0500 > From: Charles Steinmetz <[email protected]> > To: Discussion of precise time and frequency measurement > <[email protected]> > Subject: Re: [time-nuts] Isolation achieved by opamp based isoamp? > Message-ID: <[email protected]> > 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 <[email protected]> > To: Robert Atkinson <[email protected]>, Discussion of precise > time and frequency measurement <[email protected]> > Subject: Re: [time-nuts] Off-Topic Question -- German Composition > Resistors > Message-ID: > <CAMQqFu=tclbdgd5t8wgpeuiyrfjvog6-tcsd5pdpsx+-vt-...@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 > <[email protected]>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 <[email protected]> >> To: Discussion of precise time and frequency measurement < >> [email protected]> >> 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 >> >> [email protected] 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 -- [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. >> _______________________________________________ >> 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, 22 Nov 2013 14:28:04 -0500 > From: paul swed <[email protected]> > To: Discussion of precise time and frequency measurement > <[email protected]> > Subject: Re: [time-nuts] Thunderbolt Simulator > Message-ID: > <CAD2JfAgrHU_XpT2W=tsvmftf6d_grtejea47+ylfu-yxwg2...@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 <[email protected]> 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 >> _______________________________________________ >> 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: Fri, 22 Nov 2013 11:19:51 -0600 > From: Brian Lloyd <[email protected]> > To: "[email protected]" <[email protected]>, Discussion of precise time > and frequency measurement <[email protected]> > Subject: Re: [time-nuts] Crude Survey Technique > Message-ID: > <CAE3hgTdk3+g-hjik8EkgSf6TuXxtVqHxUF3zKzGrNZ_HFi=v...@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 > [email protected] > +1.916.877.5067 > > > ------------------------------ > > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > End of time-nuts Digest, Vol 112, Issue 77 > ****************************************** > > > _______________________________________________ > 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.
