| Time_Cube Statements from an aggressive adherent of "nature's harmonic simultaneous 4-day time cube." |
| Abraham_Solomon Abstract: Born in Bishopsgate, London, in August 1823. His father, Michael Solomon, was the first Jewish person to be admitted to the freedom of the city of London. At the age of thirteen he became a |
| Allan_Ramsay Abstract: Son of a poet, was born in Edinburgh on 2nd October, 1713, at thirteen he entered Edinburgh High School where he excelled at languages. In 1729 he entered the recently established Academy of |
| August_Welby_Pugin Brief biography of the Gothic Revivalist includes descriptions of his major works. |
| Augustus_Leopold_Egg Brief biographical sketch of the 19th Century painter. |
| Bernard_Partridge Cartoonist noted for strong conservative political views. (1861-1945) |
| Charles_Keene Exerpt from book about the humourist and artist available from Amazon.com. |
| David_Octavius_Hill Excerpt from book about the 19th Century painter and photographer. |
| Elizabeth_Thompson Journalist's biography and bibliography including comments on each work. |
| Ford_Madox_Brown Brief biography of the artist's life and work. Includes his Pre-Raphaelite picture 'Work'. |
| Francis_Carruthers_Gould Biography of political cartoonist who pioneered what became known as "picture politics". |
| Frederick_Walker Abstract: Son of a jeweller born in 1840. After a brief education at the North London Collegiate School, Walker found employment in an architect's office. In 1863 he exhibited his first oil paintings |
| George_Scharf Abstract: Born in Mainburg, Bavaria on 23rd April, 1788. After studying art painting and lithography in Munich, he soon found work producing lithographs for printers. In 1816, Scarf decided to emigra |
| Harry_Furniss Abstract: Son of an engineer, born in Wexford, Ireland, in 1854 he worked as an artist in Ireland but in 1876 he moved to England and found work with the Illustrated London News. Over the next eight y |
| John__Nash Brief notes on the English architect of the Picturesque movement. |
| John_Atkinson_Grimshaw Brief biography of the Leeds born Victorian artist. |
| John_Doyle Brief biographical sketch of the 19th Century lithographer, caricaturist and political commentator. Grandfather to Arthur Conan Doyle. |
| John_Tenniel Brief biographical sketch of the former staff cartoonist with Punch magazine. Best known for his illustrations for Lewis Carroll's Alice's Adventures in Wonderland (1865) and Through the Looking Glass |
| Joshua_Reynolds Abstract: Born the son of a clergyman, near Plymouth in 1723, he was sent to London to study art in 1740. After a period in Rome (1749-52), Reynolds returned to England where he established himself as |
| Linley_Sambourne Abstract: Born in London in 1844, he was apprenticed as a draughtsman in a marine engineering works in Greenwich at the age of 16. As a young man Sambourne had been a supporter of the Liberal Party bu |
| Phil_May Abstract: Born near Leeds in 1864. Orphaned at the age of nine, he endured several years of poverty moving from one job to another and ended up begging on the streets. May was a talented artist and he |
| Philip_Hardwick Abstract: Born in London in 1792. Like his father, he became an architect and the buildings he designed included the hall and library of Lincoln's Inn, Euston Railway Station, Goldsmiths' Hall and Lim |
| Richard_Doyle Abstract: Son of a cartoonist, born in London in 1824 and educated at home by his father he began having work published at the age of fifteen. Doyle, like his father, was a devout Roman Catholic, and |
| The_Royal_Academy Abstract: The first president, Joshua Reynolds, established it as a school to train artists in drawing, painting, sculpture and architecture. The Royal Academy also gave an opportunity for artists to |
| Royal_Society_of_Arts Abstract: Viscount Folkestone and Lord Romney, founded the Society of Arts in 1754. The main objective of the society was to promote the arts, productivity and trade. It was the first organisation eve |
| Rudolf_Ackermann Brief history of the lithographer and magazine publisher. |
| Sir_Charles_Barry Brief history of the 19th Century architect. |
| Sir_Christopher_Wren Short biography of the astronomer, scientist and architect who designed and built St. Paul's Cathedral. |
| Sir_George_Scott Brief biographical sketch of the 19th century architect. |
| Sir_John_Soane Brief biographical sketch of the 18th Century architect. |
| Thomas_Gainsborough Portraitist (1727-1788) who developed the theme of group portraits set in a realistic landscape. |
| Thomas_Lawrence Royal painter, knighted in 1815, and past president of the Royal Academy (1769-1830). |
| Will_Dyson Abstract: The ninth of eleven children, was born in Australia in 1880. He became a regular contributor to the Sydney Bulletin, with conservative politicians being the main target for his satire. In 19 |
| William_Kent Abstract: Born in Yorkshire in 1684, he studied painting in Rome (1709-19) and played an important role in introducing the Palladian style of architecture into Britain. He was a versatile designer. Hi |
| William_Pyne Illustrator of books about contemporary London costumes and daily life, he died while in jail for unpaid debts (1769-1843). |
| Bank_of_England Brief description and illustion of the Bank of England, established in 1694. |
| Billingsgate_Market London fishmarket officially established by an Act of Parliament in 1698. |
| Board_of_Trade Specialized department in London that oversees and regulates commerce. |
| Bow_Street_Office Location of a court house in London which housed the city's first group of constables. |
| Buckingham_Palace Short history of the royal family's principal London residence. 1703-today |
I'm not especially comfortable with the term "atomic clock" because such devicesreally just know exactly how long a second lasts. The proper name formine is the (Agilent)HP 5071A-001 Primary Frequency Standard (with high performance tubebased on cesium or cęsium for those of you outside theUS). The beginning of the second must be referenced somehow to the official internationaltime which is typically UTC(BIPM). I also have another "atomic clock", the HP5065A Rubidium vapor frequency standard (replaced some capacitors afterdiscovering major problems on boards such as A15 and A8). AlthoughRb is considered "atomic", it must bereferenced to a more official standard such as Cs (or GPS, etc).In the picture below, the light colored unit on the second shelf from the top on the right (with red LEDdigits and open panel) is my master clock,and the unit at the left of same shelf is another 5071A (above the master clock are a couple of HP 5065A rubidiums). In between those 5071As are my geodetic-quality GPS receiver from JPS (greenish) above a temperature measuring unit and a specialized Ashtech Z-12T receiver. Underneath on the left is an HP 3488A for switching, HP 5087A for distributing 10MHz. Below the master clock are some currently unused items like TST IRIG generator, 6460 & 6459 displays, pulse distribution, and amicro phasestepper. In the middle of that shelf areAgilent(HP) 53131A and53132As which are modern time interval counters, andabove is the HP 58503A GPSDO which supplies UTC(USNOvia GPS) and I use itfor 10MHz external reference to the counters. The bottom shelf containsplenty of APC UPS power and a PC, plus a Truetime NTS-200 NTP server, network equipment, cable/DSL modems, and some standard resistors. The shelf with the PC display/keyboard has space for any unit-under-test (currently holding my old HP 5370B - sometimes also a heat sinked PRS10 Rb fromSRS). The blueish digits on the counter (averaging around 155ns) show methat my clock was basically on time (after accounting for antenna/cable delays). Sometimes Hidingsomewhere is a CNSClock which is basically a TAC-2 with Motorola VP Oncore to provide me withanother UTC(USNO via GPS). I also have other spare equipment such as Austron Loran-C and disciplined oscillator, etc. At the top left is a PC running Linux hooked to a real-time GPS network, and a spare Ashtech Z-12R.To Doug Hogarth's Home Page (which has additional linksrelating to time)
What do I do with an atomic clock? I experiment comparing to otherclocks, trying to maintain my own timescale which I'll call UTC(DWH). For accuracy, I can compare to the output from a GPS-basedclock over the long term (that also shows stability over the long term). The chart below plots how well I can obtain time from the TAC when averagingover some period. The 1 Pulse Per Second output from TAC ranges about 399nanoseconds (billionths of a second) peak-to-peak and it is noisy until after acouple thousand seconds. Looks like about 6ns after a few hours, 5ns aftera half-day, and 3ns after a day. A later plot shows how short-term noisefrom the TAC can be reduced.
The next plot shows the corresponding information but instead of the TAC ituses the 58503A which ranges about 136ns peak-to-peak. The stabilitystarts out great but SA makes it get worse until around 1000 seconds where it becomessimilar to the TAC (7ns after a few hours, etc). Note that the first fewpoints should not be trusted because my resolution was about 150 picoseconds. Also, in another test it looked like the few ns level might take several days toreach and not get much better with additional days.
The next plot transitions to frequency using a more common method to presentthe same 58503A data (showing it is worst around 500 seconds). Itrepresents operation under SA; the second plot below shows how discontinuing SA dramatically improved thestability from averaging times of about one minute continuing out beyond a day. Asmentioned above, the first few points were not measured well enough. See alater chart which shows stability better than 1e-13 after a day perhapsreaching near 1e-14 after about ten days.
The plots above focus on the level which can be obtained by averaging. That is enough if I merely wanted to deal with the "rate" of my clock(frequency). But I also want my 1PPS to be aligned to the propernanosecond (phase). That requires me to know the proper WGS-84 coordinatesof my GPS antennas (so I use survey-quality methods as described elsewhere onthis site), know the antenna cable delays, know the measuring cable delays, andany other delay such as a filter inside a GPS antenna or the absolutecalibration of the receiver. I have made such attempts and I believe thatmy RegAnt has about 18ns of delay (two different L1-only antennas have similar delay), that my 58503A has about29ns of delay (some of whichis presumably due to ignoring the troposphere model), and that my JPS receiveris a few ns advanced (not counting the additional delay in the RegAnt).The following plot shows just over a day of the 1PPS from my JPSgeodetic-quality receiver with the +/-12.5ns serial message applied. It iswith single-frequency C/A. Stability seems as good as non-SA HP 58503A after about12 minutes, and looked like around 17ns peak-to-peak.
The next plot triesdual-frequency ionosphere-free which so far seems to produce results with nodramatic difference. Maybe there is a little more noise out to at least 15minutes averaging time (due to less strong signal?) and peak-to-peak is around22ns but presumably it will beless variation long term (which I will continue to track).
Since Rb might be better in the short term (<2500s) but then drifts, it can beinteresting to compare. In the plot below, we see alinear offset meaning the Rb is off frequency by about 1.15e-11.
However, after removing that linear offset, the apparent negative frequencydrift quadratic in the plot belowremains. Rb ages (drifts in frequency), in this case the estimate is~1.23e-11/month which is not quite spec (presumably due to fluctuatingtemperature).
So we remove that drift (and normalize about zero) to produce theplots below. It shows that there was a daily cycle where the peakcorresponds to overnight (cooler) - the Rb temperature coefficient is somewherearound 1.3e-12/C. Note that if drift was not removed, the stability ataround a day would be getting worse (~6e-13). Due to my equipment, periods below about 300 seconds are notproperly measured.
The plot below shows about 3.75 days from my Austron 2100R Loran-C frequency monitor (given the5071A reference), a method used before GPS to transfer frequency between remoteclocks. It starts a few seconds after lock to GRI 9940's secondary at GeorgeWA. Jumps of about 8ns can be easily seen, while the peak-to-peak is about158ns. GRI 5990 might have a little more noise?
The plot below shows why I don't use quartz frequency standards. It shows myAustron 2110 disciplined quartz (given the 5071a reference). Although thesecond-to-second data is "smooth", the peak-to-peak is ~25ns(some due to temperature changes). If that is the performance locked to an excellent standard, it ispresumably worse if looped only through my 2100R (a common setup). Due tomy equipment, periods below about 200 seconds are not properly measured.
The plot below shows how applying a negative sawtooth correction can improvethe short term (<100 seconds) noise of the TAC, and it would presumably cut off about 40ns ofthe peak-to-peak (but it has alittle problem of an ~12ns spike for a couple seconds every ~75 seconds).
Here is a half-day chart which shows that it takes a few hours after power-onfor the 58503A to "settle down."
To Doug Hogarth's Home Page (which has additional pointersrelating to time)