Re: [time-nuts] China, GCJ-02 & cartography

[Eric Scace]

I live at the edge of Boston Harbor, in the Charlestown Navy Yard.

Tide stations, such as this one at Boston Harbor’s Fort Point Channel 
, report their 
tides against a locally-defined datum 
 of mean lower low 
water (MLLW, the average of the lower of the two low tides reported each day, 
for all days observed in the current national tidal datum epoch of 1983-2001).

For this station, MLLW = +5.51 ft elevation, referenced to NAVD88.

There is a National Geodetic Survey benchmark 

 close to the tide gage. 


The  benchmark record 
 
states:
MY0555 *CURRENT SURVEY CONTROL
 MY0555  __
 MY0555* NAD 83(1986) POSITION- 42 21 18.1(N) 071 03 03.4(W)   HD_HELD2
 MY0555* NAVD 88 
 ORTHO 
HEIGHT - 4.105 (meters)   13.47  (feet) ADJUSTED
 MY0555  __
 MY0555  GEOID HEIGHT--27.738 (meters) GEOID12B
 MY0555  DYNAMIC HEIGHT  -  4.104 (meters)   13.46  (feet) COMP
 MY0555  MODELED GRAVITY -980,381.5   (mgal)   NAVD 88
 MY0555
 MY0555  VERT ORDER  -  FIRST CLASS II

As I understand it, here comes the messy part of getting from NAVD88 
geopotential geoid to WGS84 ellipsoid. I used NOAA's on-line vertical data 
transformation tool 
, using 
the 2009 May 16 benchmark recovery date specified in its record.
long = -71.0509444
lat = +42.355028
NAVD88 height = +4.105 m

The WGS84 result was:
long = -71.0509458
lat = 42.3550371
height = -24.850 m ±0.076m

   If I did this correctly, to convert from NAVD88 height to WGS84 elevation at 
this location requires subtracting 28.954m. The MLLW datum of +5.51 ft 
(+1.679m) becomes -27.275m in WGS84.

   The benchmark record above states that the 4.105m NAVD88 height is -27.738m 
height in GEOID12B at this location. One could double check the NAVD88 → WGS84 
conversion by starting with the GEOID12B height. Sadly, GEOID12B does not 
appear to be an option for the vertical data transformation tool that I used.

   But I’m a complete novice at these transformations.

— Eric

p.s.: To confuse matter further, at the moment my iPhone’s Compass tool reports 
my current height as "50 feet”. I don’t know what is the basis for that 
determination, but it doesn’t seem correct for a NAVD88 or WGS84 height.


> On 2018 May 15, at 12:13 , Bob kb8tq  wrote:
> 
> Running with a very normal WGS-84 GPS “by the sea shore” can easily show you 
> underwater. That
> is very much a normal result of the model. It does not tell you what high (or 
> low) tide level is going to
> be at your location. That stuff is simply to complex.




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[time-nuts] China, GCJ-02 & cartography

[Eric Scace]

The following was published on an email list to which I subscribe. Can others 
on this list can shed more light on CGJ-02 vs WGS-84, and some of the 
representations made in this article?

— Eric

The Problem with Chinese GPS
If you’re in a foreign country and try to read a map, you may find it difficult 
-- unless your host nation’s language is the same as your home nation’s, the 
words are going to be different and, assuming you’re not bilingual, will 
require some translation. But the locations of the roads, rivers, buildings, 
and the like should be the same, regardless of whether the map is in English, 
Spanish, or Chinese, right? Language aside, Google Maps should work the same 
everywhere, right?

Well… no.

Pictured above is a map of the China/Hong Kong border via Google Maps; you can 
see it yourself by clicking here 
.
 The map is your standard road map overlaid upon a satellite image. As you can 
see, the roads -- the light grey lines -- don’t match up with reality. There 
are roundabouts which purport to be in public parks, bridges which don’t exist, 
and multi-lane highways which seem to be underwater. The whole thing is a big 
navigational mess. Go far enough into Hong Kong, though, and the problem abates.

What’s going on? The map data, basically, is being lost in translation.

The world -- China aside -- uses something called the World Geodetic System 
1984 

 (“WGS-84”) as the basis for the digital maps. Virtually all the navigation 
tools we use online today -- the maps apps on our phones, the GPS systems in 
our cars, the missile guidance systems in use by the military, and yes, Google 
Maps -- all use WGS-84. China, though, goes its own way.

The Chinese use something called GCJ-02, an alternative system which the 
cartography world colloquially refers to it as the “Mars Coordinates” as it may 
as well be made for another planet. The Google Maps screenshot and link, above, 
shows the problem: the road map data comes from the Chinese government, which 
uses GCJ-02, but the satellite data is from a non-Chinese source and uses 
WGS-84. (As China exerts control over, and takes responsibility for mapping out 
the border between itself and Hong Kong, the problem bleeds into the 
neighboring pseudo-sovereign state.) The two data sets, effectively, are 
speaking different languages.

China isn’t just trying to be different, though; they’re trying to be 
difficult. The government has long seen map data as a matter of national 
security. There’s a “Surveying and Mapping Law of the People's Republic of 
China 
”
 which greatly restricts who can make maps. One needs a cartography license, 
one which comes with many strings; if you’re creating digital map data, for 
example, it needs to use GCJ-02 and has to be hosted on servers within China. 
And this isn’t one of those anachronistic laws which go ignored and unenforced. 
In 2015, for example, the country announced that those who violate the law 
could face fines of 200,000 yuan (about $30,000 at the time) and, according to 
CityLab 
,
 “if the violation is deemed serious enough, [those who run afoul of the law] 
can even find themselves booked on criminal charges.”

So why not just make a tool which translates GCJ-02 to WGS-84? Well, there are 
a few, but they’re typically hard to come by and not all that reliable. 
Multinational corporations like Google don’t want to deploy them as it could 
hurt their standing with the Chinese government. And even if they did, the 
results wouldn’t be great. GCJ-02 isn’t just an alternative coordinate system; 
it’s an often unpredictable one. As Wikipedia explains 
,
 “it uses an obfuscation algorithm which adds apparently random offsets to both 
the latitude and longitude.” And even if you can get around those issues, it 
won’t matter much if you’re in China itself. If you use a mobile device there, 
per Travel and Leisure 
,
 “Chinese geographic regulations demand that GPS functions must either be 
disabled on handheld devices or they must be made to display a similar offset.”

So if you're traveling to China, knowing Chinese may be a lot more helpful than 
you'd think.



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[time-nuts] Hat Creek observatory

[Eric Scace]

Hi —

   Does anyone here have contacts with the Hat Creek Observatory?

   My partner and I will be in the area Jun 15 Fri afternoon through Jun 18 Mon 
morning. While reports state the site has a few kiosks for self-tourism, we’re 
geeky time/frequency, radio & astrophysics types that want to know what’s in 
all the boxes and how everything works.

   Usually that goes better if one can be introduced.

   Thanks for any suggestions.

— Eric K3NA


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Re: [time-nuts] unidentified HF time pips

[Eric Scace]

This is a numbers station . — 
Eric K3NA

> In a message dated 2/5/2018 12:34:36 PM Eastern Standard Time, 
> je...@hanler.com  writes:
> 
> 
> Ha, so I was jumping around looking for the same and found a guy on 15.016Mhz 
> running through random characters phonetically and then signing, “this 
> completes X characters, Horsefly out.” What the heck was that?
> 
> Regards,
> 
> Jerry



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Re: [time-nuts] Some HP 10811 05071-60219 info!

[Eric Scace]

   “Wavy lockwashers” are actually a form of spring washer known as a — wait 
for it — “wave washer”.

   General design considerations and information here. 
 
Grainger and many others carry stock.

— Eric

> On 2018 Jan 16, at 12:19 ,   wrote:
> 
> Hi,
> 
> Attached is a schematic of the changes made to the stock 10811 for use in
> the HP 5071A.
> 
> Also while I recently had two of them opened I noticed wavy lockwashers
> under the nut attaching the tuning capacitor. If you have ever had to
> open one up to retighten this nut you would wish all of them had the
> lockwasher!
> 
> Cheers,
> 
> Corby<5071aefc.png>___
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Re: [time-nuts] General Radio Model 723D Precision Oscillator (Tuning Fork)

[Eric Scace]

Another fascinating tuning-fork standard was used together with a Synchronome 
to govern the timing of pulses of Morse code on undersea telegraph cables in 
the British empire’s globe-girdling telegraph network. Timing was derived 
electromagnetically from incoming Morse code signals (a bi-polar signal where 
one polarity represented a dit and the other a dah, but both dit and dah were 
of equal length) to set the master at each downstream relay/switching station 
on a cable route.

In essence, brass, mahogany and electromagnetics were use to perform all the 
functions done today on fiber optic cables: signal generation, multiplexing, 
regeneration, and timing recovery… not to mention encoding & decoding plus 
printing.

One can see a working example at the Museum of Undersea Telegraphy in Porth 
Curno, Cornwall — a museum well worth the detour to Land’s End.

— Eric

> On 2017 Dec 09, at 10:11 , Don  wrote:
> 
> Thank you, Pete.   -Don
> 
> ==
> 
> 
> 
> 
> On Sat, 2017-12-09 at 05:57 -0800, Pete Lancashire wrote:
>> Here's a look at a 723-C (1,000 cps) and how its power supply cap was
>> handled and a good look inside
>> 
>> https://www.eevblog.com/forum/reviews/vintage-teardown-general-radio-
>> 723-c-vacuum-tube-tuning-fork/
>> 
>> 
>> The GR Experimenter
>> 
>> http://www.americanradiohistory.com/Archive-General-Radio/GR%20Exp%20
>> 1941_10.pdf
>> 
>> There is another Experimenter that goes into how the tuningfork was
>> made
>> but can't find it
>> 
>> -pete
>> 
>> On Sat, Dec 9, 2017 at 5:18 AM, Don  wrote:
>> 
>>> 
 
 I was fortunate to find a vintage, General Radio (GR) Model 723D
 Precision Oscillator (tuning fork).
 
 The exceptional wooden case is as 'exciting' to look at as is the
 mechanical tuning fork inside (400Hz).
 
 As it is ac powered, I'll need to recap it before I turn it on.
  Then, we can test for accuracy! (sic).
 
 A real class-act, 'time-nut' oscillator from the last century,
 predating crystals.
 
 Don
 
 Don Lewis
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[time-nuts] Jefferts & Campbell recent papers

[Eric Scace]

These may be of interest, if the papers have not been circulated here before. — 
Eric

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[time-nuts] Fwd: A talk on Atomic Clocks by Steve Jefferts NIST Boulder Wed 11/15

[Eric Scace]

For time-nuts in the Washington/Baltimore area...

> 
> http://www.aps.org/units/maspg/
> November 2017 Event
> 
> Date: November 15, 2017
> Speaker: Steven R. Jefferts
> Topic: Primary Frequency References at NIST: Atomic Clocks
> Time and Location: 1:00 p.m., with Q to follow in a 1st floor conference 
> room at the American Center for Physics (www.acp.org ), 
> 1 Physics Ellipse, College Park, MD-- off River Rd., between Kenilworth Ave. 
> and Paint Branch Parkway.
> 
> Abstract: In the SI system of units a second is defined as 9,192,631,770 
> cycles (exactly) of the ground state hyperfine transition frequency of an 
> unperturbed cesium atom.  We take the atom to be at rest on the reference 
> geoid (~mean sea level) of the Earth.  Primary frequency standards (aka 
> atomic clocks) such as NIST-F1 & F2 in Boulder, Colorado attempt to realize 
> this definition with the highest possible fidelity.  Atomic clocks have 
> progressed steadily from fractional inaccuracies of df/f ~ 10-9 fifty years 
> ago to the best microwave clocks (NIST-F1) giving inaccuracies at the df / f  
> < 2 x 10-16  level, with optical clocks exhibiting even more phenomenal 
> performance at the 10-17 level and beyond.  This level of performance 
> requires an excruciating attention to detail when attempting to correct for 
> frequency biases.  For example, an uncertainty of 1 meter in the altitude of 
> the device with respect to the reference geoid causes a frequency uncertainty 
> of more than df / f  < 1 = 10-16 while an uncertainty in the temperature of 
> the radiation field to which the atom is exposed of 1K yields frequency 
> shifts of several times this much.  In this talk I will discuss some history 
> of these devices, the current state of the art in laser-cooled microwave 
> clocks and some fundamental limits to their attainable accuracy and briefly 
> examine some of the current uses of this level of accuracy.  New and exciting 
> laser-cooled microwave clocks for use in commercial applications and in space 
> will also be examined.
> 
> Biography:  Steven Jefferts joined NIST, Boulder, Colorado in 1994 and since 
> 1998 has been designing, building and operating the NIST primary frequency 
> references.   Steve received a BS in physics from the University of 
> Washington in 1984, and a PhD in physics from JILA - University of Colorado 
> Boulder in 1992.  He served as an NRC postdoc under Dr. David Wineland 1992 - 
> 1994 and has been a member of the NIST Technical Staff in the Time and 
> Frequency Division since 1994.  He has won a Flemming Award, two Department 
> of Commerce Gold Medals, and a Condon Award.
> 
> 
> 



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[time-nuts] MIT flea meet-up for time-nuts

[Eric Scace]

The MIT Flea  occurs this Sunday (May 21) 
from 09:00–14:00.

Come join us for a bite at Flour Café 
 at the end of the block 
(190 Mass Ave) at 11:30. I’d love to hear about your time projects & lab, see 
your trophies from the flea market, etc.

Drop me a note off-list if you can come — I’ll save you a seat at the table. If 
the weather is good, we’ll be outside.

— Eric K3NA


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[time-nuts] removing sidereal correlation

[Eric Scace]

   What other patterns, if any, are uncovered if one removes a smoothed 
sidereal variation?

— Eric

> Begin forwarded message:
> 
> From: Jim Harman 
> Subject: Re: [time-nuts] Three-cornered hat on timelab?
> Date: 2017 Apr 29 Sat at 10:14:58 EDT
> To: Bob Stewart , Discussion of precise time and frequency 
> measurement 
> Reply-To: Discussion of precise time and frequency measurement 
> 
> 
> On Thu, Apr 27, 2017 at 12:48 PM, Bob Stewart  wrote:
> 
>> So, back to my question:  Where are the large ionospheric phase moves?
>> This question has been causing me doubt since I started on this project.
>> Or don't I still have enough data collected for this to happen?
>> 
>> Bob
>> 
> 
> Bob, my test setup is a good deal simpler than yours, but attached is a
> plot that I think shows the variations you are looking for quite clearly.
> This is data from my homebrew GPSDO, which uses an Adafruit non-timing GPS
> module and a run-of-the-mill surplus OCXO. The plot records the phase
> comparator output over a period of about 1 week. The time constant of the
> PLL is 1024 seconds and it is plotting the 5-minute average TIC values.
> 
> The full horizontal scale is 24 hours.
> 
> The vertical scale shows the data from several days with the traces for
> successive days offset upwards by the equivalent of 40 nsec.
> 
> As you can see there is pretty good correlation of the phase error from day
> to day and the wiggles migrate to the left a little, corresponding to the
> 23:56:04 siderial repeat time of the GPS constellation.This is with a
> pretty good antenna location, under a shingle roof in the attic. I
> calculate the day-to-day correlation at about 0.8.
> 
> Making the time constant larger increases the variations somewhat, because
> the loop does not adjust as much, and they definitely get worse if I use a
> less optimal antenna location.
> 
> 
> 
> 
> --
> 
> --Jim Harman
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Re: [time-nuts] Time-nut going England!

[Eric Scace]

Do not neglect a visit to the Clockworks  museum. 
Examples of the most accurate pendulum clocks ever put into production e.g., 
(LeRoy, Riefler, Shortt-Synchronome and Fedchenko) are among the collection 
there. Free — and the staff are very friendly and extremely knowledgable.

— Eric

> On 2017 Apr 27, at 05:10 , Tony Finch  wrote:
> 
> Clint Jay  wrote:
> 
>> Greenwich as recommended by others is a must, the science museum is also a
>> good way to spend a day.
> 
> Look for the clock and watch gallery in the Science Museum, lots of great
> devices from the collection of the Worshipful Company of Clockmakers.
> http://www.clockmakers.org/the-clockmakers-museum-library/the-clockmakers-museum-library/
> http://www.sciencemuseum.org.uk/visitmuseum/Plan_your_visit/exhibitions/clockmakers-museum?keywords=clockmakers
> 
> And the British Horological Institute has a museum too (very limited
> opening hours, tho) http://bhi.co.uk/museum/the-bhi-museum-trust/
> 
> Tony.
> --
> f.anthony.n.finch    http://dotat.at/  -  I xn--zr8h punycode
> Fisher: Cyclonic becoming north 4 or 5, occasionally 6 at first. Moderate.
> Rain then showers. Moderate or good.
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[time-nuts] Apr 16 MIT flea gathering of time-nuts

[Eric Scace]

   Are any other time-nuts planning to visit the MIT Flea market on April 16 
Sunday? (So far I know of at least 3.)

   Contact me off-list, as we’re planning to meet for coffee/sandwiches at the 
nearby Flour café at noon. Even if you can’t make it, I’d like to meet you in 
person.

   Hopefully this can become a recurring in-person discussion of time-nuttery 
during the season.

— Eric K3NA


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Re: [time-nuts] Sinlge ADC multi-band receiver

[Eric Scace]

   This approach is known as “security through obscurity”, and is deprecated in 
the professional of information security. What one invents, another can 
discover.

   The most secure systems use well-documented algorithms with open-source 
software — widely scrutinized for bugs or implants, and therefore with 
well-understood performance limitations. The secrecy comes from good crypto key 
management.

— Eric

> On 2017 Apr 10, at 13:58 , Attila Kinali  wrote:
> 
> And they also learned
> that not documenting it is the best protection against people using it.



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Re: [time-nuts] Antique precision timing device without electronics

[Eric Scace]

   On British submarine telegraph cable systems, repeater stations and 
receiving sites employed tuning forks. Repeater sites were at cable traffic 
junctions or islands; e.g., Ascension and St Helena Islands in the Atlantic, 
Cocos Keeling in the Indian Ocean, Norfolk Island (junction) and Fanning 
(repeater) in the Pacific.

   The purpose of the tuning fork was to govern transmitted symbol rates for 
outgoing traffic. “Cable code” is a bipolar form of international telegraph 
code (almost exclusively what one hears on the radio today), where both the 
“dot” and “dash” elements have equal duration.

   Equal-duration dots and dashes saved time, meaning more revenue-generating 
traffic could be sent. This was especially important when cables had no 
compensation, and the transmission rates were extremely slow due to large cable 
capacitance.

   Dots and dashes in cable code are instead distinguished by their polarity. 
Alternating dot-dash sequences, when they occurred, created polarity reversals 
on the cable used to recover the best point for pulse sampling.

   When no telegrams were being sent, an idling polarity-reversal sequence was 
periodically injected into the cable (every 15-20 seconds or so) to maintain 
pulse detection synchronization with the distant receiver.

   The tuning fork rate was governed by a Synchronome master clock (and its 
backup). An implementation of electro-mechanical frequency control (EMFC?) 
employed a stepper relay to move the weights on the fork by small amounts to 
maintain frequency synchronization with the Synchronome. Here’s one surviving 
system, the master clock and tuning fork for PK 
 (Porth Curno), the 
landing point in Cornwall England used for most of the Empire’s submarine 
telegraph cables networks (and for many optical fiber cables today). The 
Submarine Telegraph Museum (originally established by Cable & Wireless) on this 
site is a fascinating visit.

   Frequencies around 15 Hz were common on early 20th century cables, depending 
on the degree of success in compensating for the inherent capacitance on a 
cable thousands of miles long surrounded by conductive sea water. Cable 
compensation is an entirely separate subject outside the scope of a time-nuts 
forum.

   Basically, every function we see today in fiber optic or electrical 
synchronous transmission systems (timing, encoding, transmission, pulse 
regeneration, reception, decoding, printing) was invented in electro-mechanical 
form for submarine telegraphy — and realized in beautiful brass & mahogany 
machinery.


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Re: [time-nuts] HP 115CR Clock Powerup / Documentation

[Eric Scace]

Hello Hugh & Luciano —

   Luciano: Hugh said his clock was a 115CR, not BR. The CR has the mechanical 
digital display.

   I have a 115BR that I want to bring back on the air after about 30 years of 
power-off in my father’s lab. The state of any electrolytic and tantalum 
capacitors after that much time has me concerned. I would be very happy to hear 
details of your experience in servicing the -115BR.

   Thank you.

— Eric

> On 2016 Dec 23, at 03:05 , timeok  wrote:
> 
> 
>   Hi,
>   I have the complete manual of the HP115BR. Pse contact me directly to send 
> you the file.
>   If you need I can suggest some service activity normally are needed by this 
> old clock.
>   Luciano,
>   tim...@timeok.it
> 
> 
>   From "time-nuts" time-nuts-boun...@febo.com
>   To time-nuts@febo.com
>   Cc
>   Date Fri, 23 Dec 2016 10:29:01 +1100
>   Subject [time-nuts] HP 115CR Clock Powerup / Documentation
>   Hi,
> 
>   I've been fortunate enough to acquire a HP 115CR Frequency
>   Divider/Digital Clock - it's electromechanical and I suspect built in
>   the mid/late 60s - just slightly older than your humble correspondent.
> 
>   It's similar though not identical to the 115CR shown here
>   http://www.leapsecond.com/hpclocks/
> 
>   I'd like to fire it up - given it's age my thought was to use a current
>   limited 24V bench supply and slowly ramp up the voltage the first time -
>   would welcome any thoughts on this. I gather from the supporting
>   documentation for the powersupply it's rated at drawing ~250mA
> 
>   I've been unable to locate a scan of the owners manual or service manual
>   online. Have looked at time-nuts archives, leapsecond.com and hparchive
>   to no avail. There does appear to be a hardcopy available for purchase
>   - happy to fall back to this if necessary, but any pointers welcome.
> 
>   My goal ultimately is to have it on display running, synchronised to a
>   GPS disciplied 10MHz source :)
> 
>   Any thoughts and feedback welcome - this is my first foray into old
>   clocks :)
> 
>   Kind Regards,
>   Hugh
>   VK3YYZ/AD5RV
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Re: [time-nuts] 1PPS users?

[Eric Scace]

Speaking as an owner of a well-behaved mechanical clock:
Clock rate performance over time can be done based on time interval 
measurements anchored to a solid frequency standard. No 1pps needed per se.
Bring a clock to time is simplified with a timescale-accurate 1pps source.

> On 2016 Dec 18, at 18:16 , Bob Stewart  wrote:
> 
> One thing I've never really understood is who actually uses the high-quality 
> 1PPS output from a GPSDO.  I have spent a lot of time, effort, and money on 
> developing my GPSDO without a whole of thought to the user base.  It was just 
> a quest for the best result I could obtain with a particular technology.  The 
> frequency standard users was a no brainer.  Everyone who wants a frequency 
> standard eventually understands they need to get a GPSDO, or an Rb, or a Cs.  
> And that's all I thought I had: a good frequency standard.  And then Tom 
> prodded me a bit and showed me the shortcomings of what I was doing, and I 
> did something about it.  So, if an NTP user can get his time fix directly 
> from a noisy receiver, who actually needs a time-accurate, low jitter 1PPS 
> pulse?
> Bob - AE6RV

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Re: [time-nuts] Time math libraries

[Eric Scace]

   I should clarify my intended application for “time math”.

   My company is deep in development of a system that, in part, records events 
on a blockchain. For various reasons a precise and accurate representation of 
time of the event can be important. How precise and accurate depends on the 
application. The first applications need millisecond precision and tens of 
millisecond accuracy — not a huge demand by TimeNut standards, but not to be 
neglected. Leap seconds (and the differing contortions being used by various 
organizations to evade implementation of leap seconds) should not be ignored.

   The blockchain runs as a generic event-recording ledger utility supporting 
many applications. Over time, we will need to get more precise and accurate on 
time.

   To be general, we take the following approach:
Timestamp (and, often, geolocation) are acquired at the point of measurement 
for the data set. This is treated as the opinion of the collecting device. We 
record meta-data about the collecting device. For some applications the 
meta-data includes information as to how the device formed its opinion of time.
The application submits the event to the ledger service’s API for recording.
The API server(s) timestamp the client’s request to record to the ledger. This 
timestamp is relatively important because it is the declaration of the ledger, 
an immutable reference of the sequence of events, upon which other systems will 
rely in future.

   The present scheme is to use TAI as the timescale for all events recorded to 
the ledger. Some of the implications:
Collecting device timestamps may need to be convertible to TAI.
This task can be a mess, because the sources of time opinions may be vast; 
e.g., cell phones, AWS, Google, MS Azure, etc. We work around this by capturing 
meta-data about the device’s timescale and source. This allows retrospective 
consideration of the devices’ time opinion relative to TAI when it is important 
for the downstream data consumer.
Independent systems participating in the blockchain (e.g., as API server, or as 
consensus-forming systems) should have consistent opinions of TAI.
Ledger timestamps (in TAI) need to be converted to the data consumer’s desired 
time scale.
Here’s another instance of the need for a set of time math utilities.

   I realize this description also opens a Pandora’s box that involves 
distribution of time issues. But, for the purposes of this thread, I wanted to 
focus on the TAI-to-other-timescales conversion utility question.

   If good timescale conversion utilities exist, we would use them.

   If good timescale conversion utilities do not exist, then maybe we’ll 
contribute one to the open software space.

— Eric
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[time-nuts] Time math libraries

[Eric Scace]

   (Apologies if this question has been addressed before. Archive search is 
rather cumbersome on a month-by-month basis.)

   Few people will be surprised to learn that MS Excel does not account for 
leap seconds when doing time math. See below for an example. This is just an 
example of many instances of programming failures.

   Are there good time math software libraries (e.g., Java, C++/C#, etc) that 
will do time math correctly for the chosen time scale?

   Thanks.

— Eric


2016 Dec 31 Sat 23:59:57
2016 Dec 31 Sat 23:59:58
2016 Dec 31 Sat 23:59:59
2017 Jan 01 Sun 00:00:00
2017 Jan 01 Sun 00:00:01
2017 Jan 01 Sun 00:00:02


My machine is on EST right now. Is it a time zone question?

2016 Dec 31 Sat 18:59:57
2016 Dec 31 Sat 18:59:58
2016 Dec 31 Sat 18:59:59
2016 Dec 31 Sat 19:00:00
2016 Dec 31 Sat 19:00:01
2016 Dec 31 Sat 19:00:02

Nope!

What about past leap seconds?

2015 Jun 30 Tue 23:59:57
2015 Jun 30 Tue 23:59:58
2015 Jun 30 Tue 23:59:59
2015 Jul 01 Wed 00:00:00
2015 Jul 01 Wed 00:00:01
2015 Jul 01 Wed 00:00:02

Also fail!
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Re: [time-nuts] HP Z3801A

[Eric Scace]

Hi Joe —

   I’ll take the HP-58516A splitter, if you’re willing to see it separately.

— Eric K3NA

> On 2016 Nov 27, at 14:15 , Joseph Gray  wrote:
> 
> I'm selling my remaining Z3801A. Months ago, I replaced the original
> GPS module with a more sensitive Oncore VP. At that time, I also
> replaced several suspect capacitors on the DC-DC converter board.
> Everything has been 100% since. The RS-232 mod was done long ago.
> 
> A serial cable and a 24 VDC power supply is included. I will also
> include a spare Oncore VP module for free. Asking $300 plus
> shipping/insurance.
> 
> I also have an HP 58516A 4-way GPS splitter that I will include for $50 more.
> 
> Joe Gray
> W5JG
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Re: [time-nuts] Thinking outside the box a super reference

[Eric Scace]

Kickstarter?

> On 2016 Nov 03, at 16:07 , Bert Kehren via time-nuts  
> wrote:
> 
> 
> Over the past there has been talk about building from  scratch high 
> performance references. I think consensus was that it is out of  reach. In 
> the mean 
> time Corby is reworking an active maser which takes a lot of  know how. But 
> let us look at his work on the super HP5065. It is able to  outperform a 
> passive maser in the below 100 second range! Long term a proper  GPSDO should 
> be possible to step in. We are working on it including pressure and  
> temperature control. To make full use of it you also need to have the 
> capability  
> to monitor, record and analyze on a continuous basis preferably with out 
> tying  up expensive equipment. We have the pieces in place and looking 
> forward 
> of  combining all the pieces and compare with Corby’s active Maser. We are 
> back to  the GPSDO after being distracted by Tbolt performance. A third party 
> is working  combining the GPSDO data stream with the data from the unit that 
> generates  frequency, pressure and temperature data along with time to a 
> USB stick, while  also be able to monitor with a PC.  
> I know it is considered by some heresy but our lack of a  Maser and in Juerg
> ’s case no access to one, we try to overcome it with a GPSDO  tailored for 
> Rb and Cs and control our Cs’s C field .   
> There was a time that I did have a HP5065A but got rid of  it when I got 
> some Cs’s. My best counter was A HP5345 and even with a Tracor 527  1 second 
> performance was not an issue. That changed when Corby introduced me to  time 
> nuts and frankly it was the first  time I learned about ADEV. But the 
> HP5065A was gone. Now I have a cell  that Corby has plotted and time 
> permitting 
> may become a project. 
> Let me get to the real issue. There are not enough  HP5065A’s out there and 
> not affordable for all time nuts. Most are being kept  and are not for 
> sale. But if a combined effort by many time nuts it MAY be  possible to 
> recreate 
> the guts of the HP5065A. The key word is MAY. 200 time nuts  be willing to 
> invest $ 5000 each may get us there. The market does not justify  such an 
> effort but time nuts keep bringing up discussions. All the other ideas  
> kicked 
> around in the past will cost more. There are some among us that know what  
> it cost and who can make the key elements like lamps, cells, filters etc. 
> Just a  thought outside the box and hopefully may turn in to a limited 
> constructive  dialog. We will continue on our path, which include FRK/M100, 
> HP5065 
> and  Cs. 
> We would not be capable to contribute technically on the  physics package 
> but I would be willing to contribute financially and with  monitoring 
> equipment even if I would not be around when finished. 
> Bert Kehren
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Re: [time-nuts] Temp/Humidity control systems?

[Eric Scace]

   Ha!

   That is the system my brother Greg Scace designed and built while at NIST. 
He has given a lot of papers around the world on its metrology technology.

   On the side, he manufactures the reference calibration tools for espresso 
machines 
<https://www.espressoparts.com/scace-2-espresso-machine-thermofilter-temperature-pressure-device>.

   Greg is still working there… as is his wife Casey (on cryptography)… and my 
father Bob Scace worked there for 25 years on microelectronics and 
nanotechnology… my other brother Brian retired recently from NIST… and I worked 
there for a few years 1978-1981 on international data networking problems. I 
think the Scace family has the record for maximum number of family members 
employed at NIST.

— Eric Scace

> On 2016 Oct 27, at 13:32 , William H. Fite <omni...@gmail.com> wrote:
> 
> Just for the fun of it, here is how NIST measures humidity.
> https://www.nist.gov/sites/default/files/documents/calibrations/sp250-83.pdf
> 

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[time-nuts] Ig Nobel ceremonies & time

[Eric Scace]

I had the happy fortune to attend this year’s Ig Nobel award ceremonies, the 
agenda of which is found here . This was 
the 26th First Annual Ig Novel Prize Ceremony

This year’s program featured “time”, including:
a mini-opera “The Last Second”, whose plot involves a leap second that goes 
very wrong.
micro-lectures by:
Prof Jenny Hoffman, Harvard physics: “What is a Leap Second, and Why Do We 
Create Them?”
John Lowe (NIST, Boulder): “How Scientists Decide When to Create a Leap Second, 
and How We Do It”
Eric Maskin, Nobel laureate, economics: “The Kinds of Financial Mischief That 
Could Be Done During an Unannounced Extra Leap Second”
Each time the word “time” was mentioned, the cheerleading section of the 
audience groaned.

All the micro-lectures were excellent — and John Lowe especially so. You can 
listen to it, the opera, and all the rest of the ceremony, on the upcoming Nov 
25 “Science Friday” program on public radio. Broadcast times here 
. Or, if impatient, the entire ceremony is 
available on YouTube  now.

I now return you back to our usual programming… 

— Eric
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Re: [time-nuts] GPS antenna selection — lightning

[Eric Scace]

Unfortunately, an antenna, cable, or piece of electronics located indoors is 
just as susceptible to lightning surges as one that is outdoors.

Lightning-induced surges couple into these systems electromagnetically across a 
wide range (VLF to SHF) of frequencies. When you think about your home from an 
electromagnetic viewpoint, just imagine your structure with all non-conductive 
materials absent. For a typical wood or brick/stone house in North America, 
what you are left with is:
metal plumbing pipes and fixtures, with their geometry suspended in space
house wiring, CATV, Ethernet, and telephone cabling, and their service drops, 
all suspended in space
electrical & electronic circuits of every kind (WiFi note, computer, 
appliances), their power supplies and AC power cords, also suspended in space
metal furniture? That’s hanging out there, suspended in space, too.
any I-beam or other steel structural elements, some random aluminum flashing, 
door knobs, and other similar metal construction materials used in the home.
That is what an electromagnetic pulse sees as it approaches and sweeps over 
your home… all hovering over a lossy ground plane (earth) its varying 
dielectric constant.. Each one of those pieces of metal, hanging in space, is 
an unintentional antenna that experiences voltage differentials and current 
flows.

A GPS antenna and its coax line that is installed next to a window is no 
different from the same antenna/coax installed one meter outside the window… or 
10 meters away outside the window. All three installations are effectively 
“outdoors” from an electromagnetic viewpoint, and all three need effective 
surge protection from lightning-, cloud-, and precipitation-induced voltage 
surges.

(N.B.: Snow can be particularly bad for voltage surges. I’ve seen thousands of 
volts per meter potential differences in moderate-to-heavy snowfall that 
produced very significant current flows on cables.)

Surge protection for your antenna, its attachment to your receiver(s), AC/DC 
power supply lines, and any other signal lines of significant length is cheap 
insurance.

My continuously-operating electronics lives in an enclosed rack cabinet — not 
too much worse than a proper Faraday cage. Every cable entering the cabinet has 
surge protection at the point of entry. The cabinet is bonded to earth ground 
by 2” copper flashing. In the past this system lived 22 years on a mountaintop 
home, 1200 ft above surrounding terrain. Lots of thunderstorms — zero 
damage/disruptions during that time… a sample size of one, admittedly, but 
during the first 18 months at that site I had two lightning-surge damaging 
events before I got serious about protection.

I have equipment at a coastal site with multiple 130-ft towers. That site had 
damage events every 2 years or so — even when cables to the “outside” were 
disconnected, and AC mains power was shut off at the main circuit breaker box. 
After implementing comprehensive surge protection, we have had zero damage over 
the last 12 years.

— Eric

> On 2016 Aug 04, at 19:46 , Bob Camp  wrote:
> 
>>> Grounding the antenna is always a good idea.
>> 
>>> A surge suppressor in the line could save you some
>>> real cost if there is a lightning strike.
>> 
>> I did a quick search for SMA/BNC/TNC based surge
>> protectors and not much did come up, any suggestions
>> what to use there?
> 
> There are a *lot* of them on eBay. Many of them have N connectors on them.
> 
>> 
>>> I don’t know about Austria, but here in the US,
>>> both are required.
>> 
>> Outside definitely, "inside" I'm not sure, but it
>> won't hurt to have additional protection for the
>> receiver(s).
> 
> It is a good bet that the antenna will be outside. I’d plan it that way.



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Re: [time-nuts] Visiting Greenwich

[Eric Scace]

Also in London, and not to be missed, is James Nye’s Clockworks Museum 
 of precision astronomical regulators and 
electro-mechanical clocks, including working examples of each of the successive 
generations of top-accuracy pendulum clocks (Riefler, Shortt-Syncronome, 
Fedchenko).


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[time-nuts] O-451A/u 5 MHz oscillator: more photos

[Eric Scace]

   I added some more photos of the O-451A/U to a Dropbox folder 
. 
There are no obvious manufacturer marks beyond the Western Electric contractor 
cited on the Coast Guard nameplate on the front panel. Note that the large 
electrolytic cap and transformer are a quick & dirty mod to bypass the 
dynamotor in the supply.

   In opening the rear of the unit to compare with the photos Corby sent on Jun 
2nd, the dynamotor prevented me from removing the insulation plug in the back. 
But the guts in the front of the unit are identical (other than my father 
thoughtfully added a spare tube inside when he was working on it).

   The O-451A/U puts out 5, 1 and 0.1 MHz square wave… implying a 5 MHz crystal 
inside the double oven. The rear panel photo includes a marking that describes 
the crystal as a GA-10752.

   As mentioned in an earlier email, these oscillators appear to have been used 
in Loran A/B transmitter sites. The last in-service date shown on the inside of 
the dropdown front panel for this particular unit (serial #11) is 1974. If 
there was a separate calibration logbook, it was lost when the unit was 
declared surplus.

— Eric
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Re: [time-nuts] Mystery hp Ovens For Sale

[Eric Scace]

http://www.loran-history.info/Johnston_Island/Johnston%20-%20OSC%20Msg%20221416Z%20Oct%2064.pdf
 states than an O-451/U oscillator was shipped to the Johnston Island LORAN 
station in 1967. We are getting closer...

I am the owner of O-451A/U serial number 11. I would appreciate any 
documentation that people uncover. Although the USCG property tag says Western 
Electric was the contractor, some have suggested the construction reminds them 
of General Radio practices...

Thanks, all.

— Eric K3NA

> On Jun 5, 2016, at 03:18, Poul-Henning Kamp  wrote:
> 
> 
> In message , cdel...@juno.com writes:
>> Got an email from someone who has the main unit!
>> 
>> Found out that the assy. is from an O-451A/U.
>> 
>> Possibly coast guard.
> 
> Could be the original LORAN-A/B timebase...
> 
> As far as I know, LORAN-C was the first with Cesium
> 
> 
> -- 
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
> p...@freebsd.org | TCP/IP since RFC 956
> FreeBSD committer   | BSD since 4.3-tahoe
> Never attribute to malice what can adequately be explained by incompetence.
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Re: [time-nuts] GENIUS by Stephen Hawking (PBS TV), with 5071A cesium clocks

[Eric Scace]

For those of us who do not have TVs, pointers to an Internet source for viewing 
the show would be welcomed. Thanks!


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Re: [time-nuts] Western Electric O-451A/U double-oven XO

[Eric Scace]

> On 2016 Apr 26, at 16:25 , paul swed  wrote:
> 
> Tom,
> Thanks for sharing the photos.
> 
> Comments
> It looks like most of the items will clean up very well with a bit of TLC.

   Agree. That won’t be hard. Mostly sawdust from cellar storage at my parents’ 
home.

> Tom it may be you actually who wrote about the clock and getting it working.
> Either way I am pretty sure Eric can find helpful details before he applies
> power.

   The mystery unit is the double-oven XO in the bottom unit. We (my father and 
I) have had that operational and did a year’s worth of phase comparisons with 
WWVB back around 1980. Unfortunately I haven’t found the chart recorder strips 
from those runs. But I don’t expect any problems to get the equipment 
operational again with a cleaning and re-capping.

> The same goes for most of the rest of the gear. The old caps may have a
> nasty surprise waiting.

> Eric the WWVB receiver will no longer work with the new WWVB modulation
> format. I assume it was a typical TRF radio of the 1960-70s vintage.

   Ha! This was a home-brew from scratch by my father in 1979. (He got the bug 
when I brought home the DOCXO and HP-113BR. Working at NBS/NIST also helped.) 
But yes, it doesn’t pay any attention to the modern modulation format. The 
receiver/comparator’s goal was to establish a “clean” 60 kHz signal that was 
phase-locked to WWVB with some moderate time constant short enough to easily 
detect the intentional phase shift of WWVB’s signal at the time — and then 
perform the comparator task against local sources and drive a chart recorder 
with the results. If folks are interested, I’ll post his “as built” photos and 
circuit diagram when I unpack the documentation.

   Sadly, since the start of this year my father has been existing in a 
dementia wing at a graduated living facility. Restoring this equipment to 
service in my home is an emotional homage to the man who taught me so much 
about practical electronics. Thanks, Dad — I miss you.




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[time-nuts] Western Electric O-451A/U double-oven XO

[Eric Scace]

Hi —

   I have finally retrieved from my parents’ home my original time & frequency 
standards lab, to which will be added my more recent HP Z3805A. The assembly 
contains:
HP-113BR frequency divider/clock
homebrew WWVB receiver & frequency comparator, with its own internal OCXO 
standard, that my father and I built in 1979 to maintain calibration and 
otherwise measure the performance of its internal OCXO standard and of the 
following…
Western Electric O-451A/U double-oven frequency standard. As you will see from 
the photos, this unit was made for the US Coast Guard. The double-oven is on 
shock mounts and the power supply contains a dynamotor — signs of shipboard 
use, although I suspect it was part of a coastal radio station. We bypassed the 
dynamotor supply and installed a more modern supply.

   Unfortunately I never had any documentation for the O-451A/U unit. I wonder 
if anyone else has experience with this oscillator, or has any documentation. 
Since it hasn’t been operating in the last 30 years, I’d like to replace the 
electrolytics capacitors — but this would be much easier with documentation.

   A quick Internet search did not yield a reference manual. Given that this 
unit is serial number 11, I supposed I should not be too surprised.

   Any suggestions for finding reference manuals for the O-451A/U?

   Thanks.

— Eric







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[time-nuts] Western Electric O-451A/U double-oven XO

[Eric Scace]

Hi —

   I have finally retrieved from my parents’ home my original time & frequency 
standards lab, to which will be added my more recent HP Z3805A. The assembly 
contains:
HP-113BR frequency divider/clock
homebrew WWVB receiver & frequency comparator, with its own internal OCXO 
standard, that my father and I built in 1979 to maintain calibration and 
otherwise measure the performance of its internal OCXO standard and of the 
following…
Western Electric O-451A/U double-oven frequency standard. As you will see from 
the photos, this unit was made for the US Coast Guard. The double-oven is on 
shock mounts and the power supply contains a dynamotor — signs of shipboard 
use, although I suspect it was part of a coastal radio station. We bypassed the 
dynamotor supply and installed a more modern supply.

   Unfortunately I never had any documentation for the O-451A/U unit. I wonder 
if anyone else has experience with this oscillator, or has any documentation. 
Since it hasn’t been operating in the last 30 years, I’d like to replace the 
electrolytic capacitors — but this would be much easier with documentation.

   A quick Internet search did not yield a reference manual. Given that this 
unit is serial number 11, I supposed I should not be too surprised.

   Any suggestions for finding reference manuals for the O-451A/U?

   Thanks.

— Eric







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Re: [time-nuts] GPS jumps of -13.7 us?

[Eric Scace]

   I have an idle curiosity as to whether the erroneous UTC correction 
propagated into any high-speed trading platforms in the financial markets in a 
what that caused a disruption.


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Re: [time-nuts] "Selective availability" af accurate time for Appleusers?

[Eric Scace]

Warning: the following may be apocryphal. I was once told:
Sprint PCS networks distributed very accurate time to cell phones because GPSDO 
& accurate time was essential to the multiplexing technology then in use.
In contrast, time of day at an AT GSM cell site depending on the accuracy of 
the technician’s watch when setting up the site. Hence, each site could be many 
seconds different from its neighbors.
I have never verified this information, and it is 10 years old.

> On 2015 Oct 21, at 01:41 , David J Taylor  
> wrote:
> 
> Has anybody else observed this with their iPhone since “upgrading” to iOS 9? 
> Anyone know of any difference in the reference time ( e.g. GPS vs. network 
> time) that Apple is using to “dumb down’ their smartphones in favor of Apple 
> Watch?
> 
> Brian Garrett
> 
> 
> Yes, on one quick check, I now see an accuracy (or rather error) o my iPad of 
> up to several seconds (iOS 9.0.2) compared to my recollection of sub-second 
> accuracy under iOS 8.0.2x.
> 
> My £50 Windows 10 tablet using real NTP does /much/ better!
> 
> Cheers,
> David
> --
> SatSignal Software - Quality software written to your requirements
> Web: http://www.satsignal.eu
> Email: david-tay...@blueyonder.co.uk
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Re: [time-nuts] UPS for my time rack

[Eric Scace]

I’ve used Anderson PowerPoles in mixed voltage environments successfully. A 
visual indication can be obtained by using other colors for the connector 
shell; e.g., red for +13 Vdc and blue for +25 Vdc…

One can also re-orient one of the connectors in each pair by 90º or 180º to 
create a physical incompatibility. This takes some care as the cable ends are 
no longer interchangeable, but it does provide protection against connecting to 
the wrong voltage.

— Eric K3NA

> On 2015 Oct 13, at 16:52 , Florian Teply  wrote:
> 
> Am Tue, 13 Oct 2015 18:54:58 +
> schrieb "Poul-Henning Kamp" :
> 
> […snip…]
> Umm, around here, at least for ham radio operators, it seems many
> standardize now on PowerPole connectors for 12V DC. They are pretty
> affordable, running at below 2 Euro for a single pair. Sure, it's not
> as cheap as an USB connector, but they are designed to handle
> significant currents (15, 30, 45 amps which are freely interchangeable,
> versions rated for 75 or 120 amps exist also).
> 
> Now of course if you want to mix voltage levels, things might become a
> bit more complicated, as most 12V equipment doesn't like to be supplied
> with 24 volts, so it might actually not be the brightest idea to use
> identical connectors in such circumstances. Don't ask how I know... ;-)
> 
> Of course, short circuit currents are the same as before, so properly
> rated fuses and/or circuit breakers are a must, but that would be
> recommended for mains powered equipment as well.
> 
> Best regards,
> Florian


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