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-requ...@febo.com> > To: time-nuts <time-nuts@febo.com> > Sent: Fri, Nov 22, 2013 6:29 am > Subject: time-nuts Digest, Vol 112, Issue 75 > > > Send time-nuts mailing list submissions to > time-nuts@febo.com > > 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 > time-nuts-requ...@febo.com > > You can reach the person managing the list at > time-nuts-ow...@febo.com > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of time-nuts digest..." > > > 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.bori...@screen.it> > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] Motorola M12+ > Message-ID: > <cal8xpmppu6e2g90veafkzmdqvpmse+ql+uxr6+rcvhuueyd...@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.arb...@securimar.com> wrote: >> I am wondering if this is a sustitute of the original oncore VP >> receiver for > the Z3801 -Z3805. (E-pay 281161070304 ) >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> 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 00:18:50 +1300 > From: Bruce Griffiths <bruce.griffi...@xtra.co.nz> > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] Isolation achieved by opamp based isoamp? > Message-ID: <528f3d9a.5090...@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<ssandenbe...@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<csteinm...@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 >>>> >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@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@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > > > ------------------------------ > > Message: 3 > Date: Sat, 23 Nov 2013 00:15:15 +1300 > From: Bruce Griffiths <bruce.griffi...@xtra.co.nz> > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] DMTD: Mixer DC offset will result in time > offset at zero-crossing detector out? > Message-ID: <528f3cc3.9010...@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@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 <ssandenbe...@gmail.com> > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] Crude Survey Technique > Message-ID: > <CADbj3vY8unLvjeE77Kh=T3pO5bGyUK=REjXeLEoRM-P+=42...@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, <johncr...@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 >> >> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@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, 22 Nov 2013 07:06:28 -0500 > From: Bob Camp <li...@rtty.us> > To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] Strange 100ns jumps on Motorola M12+T > Message-ID: <01d166a8-d93a-4b4d-b195-606a6a0de...@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 <ssandenbe...@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 <li...@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.bori...@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 <li...@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 <t...@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@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@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@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@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@febo.com >> 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 14:19:26 +0200 > From: Stephan Sandenbergh <ssandenbe...@gmail.com> > To: Discussion of precise time and frequency measurement > <time-nuts@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=anvnsujnwn...@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.griffi...@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@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@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@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > End of time-nuts Digest, Vol 112, Issue 75 > ****************************************** > > > _______________________________________________ > time-nuts mailing list -- time-nuts@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@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.