Hi If you dig back far enough in the archives, you can find information that suggests the Thunderbolt uses carrier phase data.
Bob On Mar 15, 2010, at 8:15 PM, Bruce Griffiths wrote: > WarrenS wrote: >> >> Bruce wrote: >>> "Which antenna performance metric do you have in mind?" >> Could do GPSDO hold over performance, but that would not be much of a test >> of the antenna. >> How about the antenna's effect on the ADEV Osc noise and Phase noise. >> What else does the Time Nut care about? >> >>> Since the better timing receivers use carrier phase ... >> I don't remember you ever finding ANY Time Nut that is now using one. >> So may be simpler for now to just stick to the more common type of GPSDO in >> use. >> > The Motorola M12+T and iLotus M12M use carrier phase smoothing of the code > phase observables. > > Its highly likely that a number of the better performance GPS timing > receivers also use carrier phase smoothing. > > Thus whether one is aware of it or not the antenna carrier phase properties > are likely to be of some importance. > > In the absence of complete information on how your particular GPS timing > receiver uses carrier phase and code phase observables, the best you can do > is compare the performance of a range of antennas using a given timing > receiver. > > Such results will only apply to a particular site and receiver. > Specifying the pertinent characteristics (eg isolated on a flat plain, > surrounded by a set of hills, mountains which obscure the sky below 10 > degrees, surrounded by trees that obscure everything below 40 degeees > elevation, etc) of your antenna location and the particular GPS receiver used > will be helpful to others in selecting an antenna that suits their budget, > receiver, antenna location constraints, etc. > > Bruce > >> ws >> >> ************* >> Bruce said: >> >> Which antenna performance metric do you have in mind? >> There are several, some of which are considered in the paper: >> http://www.novatel.com/Documents/Papers/effectofantenna.pdf >> >> Since the topography surrounding the antenna, its height and location on >> the Earth all affect measured performance any comparative measurements >> should use the same receiver and antenna location. >> >> Some estimates for the effect of multipath on code phase receivers can >> be found: >> >> http://bbcr.uwaterloo.ca/~wzhuang/papers/iee95_gps.pdf >> >> http://bbcr.uwaterloo.ca/%7Ewzhuang/papers/iee95_gps.pdf >> >> Since the better timing receivers use carrier phase smoothing of the >> code phase timing, both the carrier phase and code phase performance of >> the antenna are important. >> >> A phased array antenna like the one in the following papers may provide >> better performance than alternative antennae: >> >> http://www.navsys.com/Papers/0001002.pdf >> http://www.congrex.nl/07c12/papers/day1_s1_paper05_Konovaltsev.pdf >> >> Some measurements with geodetic antennae: >> http://www.fig.net/pub/fig2008/papers/ts05g/ts05g_03_eventzur_shaked_2816.pdf >> >> >> Comparison of code phase and carrier phase time transfer: >> http://tycho.usno.navy.mil/ptti/ptti2004/paper41.pdf >> >> Bruce >> >> ****************** >> WarrenS wrote: >>> Brian wrote: >>> >>>> "There were also comments about surveying and timing antennas." >>> Those may of been from me, unsuccessfully trying to make a point of >>> the difference between what is 'Best' and what is 'GOOD enough'. >>> >>>> "about every national timing laboratory uses choke ring antennas. >>>> ... for timing stability reasons." >>> Then again they also have multiple CS and Just their Antenna budget is >>> likely more than the annual income of most time nuts. >>> Can you do a test to show IF there is ANY improvement for the AVERAGE >>> time nut when compared to a well setup (Tbolt) GPSDO using a TacoSalad >>> antenna? >>> >>> Would be interesting to see a plot of cost vs. performance for the >>> various antenna types, >>> Scaled to show the performance improvement that the average Time nut >>> would see. >>> The TacoSalad antenna, originally cost me a total of $7.95, And took >>> under 30 seconds to build. >>> That cost should be discounted because those parts had been considered >>> just throw away junk up until now. >>> >>> ws >>> >>> ********************** >>> >>> ----- Original Message ----- From: "Brian Kirby" >>> <kilodelta4foxmike at gmail.com> >>> To: "Discussion of precise time and frequency measurement" >>> <time-nuts at febo.com> >>> Sent: Monday, March 15, 2010 2:09 PM >>> Subject: Re: [time-nuts] Choke Ring Pictures >>> >>> >>>> Dr. Clark passed on a tip that I used. Put the funnel in a microwave >>>> oven and run it and see if the funnel warms up. If it warms up, you >>>> do not use it. I do not know what type of plastic the funnel was >>>> made out of; it was white, semi-transparent. >>>> >>>> There were also comments about surveying and timing antennas. If you >>>> investigate about every national timing laboratory uses choke ring >>>> antennas. Some enclose the antenna unit and they temperature control >>>> it. They do this for timing stability reasons. >>>> >>>> The commercial timing antenna is bullet shaped and is operated >>>> without a ground plane. They are patch antennas. When there is not >>>> ground plane, the antenna picks up best from the overhead and less >>>> towards the horizon. These antennas usually have a lot more gain >>>> (30-50 db vs most normal antennas in the 15-25 db range). >>>> Also in surveying, we cut off the horizon at 15 degrees in software. >>>> A free Army Corp of Engineering manual on GPS Surveying is at >>>> http://140.194.76.129/publications/eng-manuals/em1110-1-1003/toc.htm >>>> The main difference in surveying and timing is in surveying they use >>>> the carrier phase method, were in timing most use a solution derived >>>> from the processing of the coarse acquisition code, in were the >>>> receiver is in a fixed over-determined position . Some timing labs >>>> are using carrier phase method, when they need more resolution. >>>> >>>> Brian - KD4FM >>>> >>> **************** >>>>> warrens wrote: >>> ... >>>>> Preliminary results for the Taco Dish GPS antenna as an indoor >>>>> antenna are looking good. >>>>> Certainly worth considering if your GPS antenna is stuck indoors, >>>>> 'Out of the rain in the living room'. >>>>> I find it best to rise it up near the ceiling such as on an upper >>>>> shelf with nothing above it. >>>>> It would be hard to tell the difference between the GPSDO >>>>> performance obtained from this or the Best outdoor antenna if using >>>>> a Tbolt set to the standard default settings. >>>>> Picture attached >>>>> >>>>> ws >>>>> >>>> ************** >>> >> >> >> _______________________________________________ >> 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.
