In message 06013AA10880459380352E3FB29C4B5C@pc52, "Tom Van Baak" writes:

The first input you need is the exact longitude/latitude of the
lightning bolt.

The easiest way to do that is with a set of GPS synchronized receivers,
aaaand we're back to sqare one!

The next issue is that lightnings are seldom vertical, they can
trivially wiggle many hundred meters sideways, so at absolute
best your jitter is going to be no better than the microsecond
domain, and probably much worse, increasing with distance.

But there's a workaround:  if you have the right kind of "pregnant"
thundercloud overhead, a plain firework rocket trailing a thin
grounded wire will, on your command, get you a lightning strike.

Not only are these lightnings almost always entirely vertical, they
are also particular sharp and potent (for that very reason).

So if you live in the right kind of place, you could implement
a daily clock synchronization service much more spectacular
than a mere "ball-drop".

I belive the US electrical grid industry runs a joint research
center somewhere in northern Florida, using this method to test
lightning protection of the power grid components.

I suspect they ignite their rockets using remote control.

--
Poul-Henning Kamp      | UNIX since Zilog Zeus 3.20
phk@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.

That's true for ultimate accuracy. But notice how each strike is seen by dozens of observers and each observer knows their (fixed) position and has their own local (approximate) clock.

So it seems to me it's not unlike how GPS works: with enough samples, it should be possible to solve for latitude, longitude, and time of each strike. Like running GPS in 3D mode rather than position hold (zero D) mode.

Now the accuracy is clearly not going to be at the nanosecond level. Maybe not even microsecond level, since as you mentioned, there are biases and jitter and who know what propagation variations.

But over time, you should be able to converge on differential local clock measurements. What I'd like to see is the TDEV of this as a common view time transfer method. A couple of hops and we could compare UTC(PHK) with UTC(TVB), for example.

Perhaps another side effect of their lightning project is that it could create dynamic propagation maps using the residuals in their massive database. When I first owned WWVB gear I thought I had accurate time. After I got GPS, I realized that my WWVB receivers now became accurate Colorado-to-Seattle weather stations. As they say, one man's error is another man's signal.

/tvb

as, ahem, one of the early experimenters of lightning detection, gotta tell
ya, the return stroke risetime is on the order of 1 us. Also, the very
beginning of the waveform, that is the first part of the spike, is connected
with the beginning of the breakdown, hence the location on the ground.
Subsequent parts of the waveform are due to higher portions of the channel.
Also, there are two polarities of discharge, and the "positive" discharge
gives a waveform that looks like a cloud discharge that does not strike ground
at all. Those seriously interested should get hold of a copy of "Lightning" by
Martin Uman; this is bby now old, but is available inexpensively and will get
you started. The original detectors used wideband crossed loops to get
direction and no time of arrival; well before GPS timing. I hadn't looked into
the "amateur" network!
Vaisala corp has the best USA net, otherwise there is one in Boston and TOA
enterprisesin Florida. U of Washington has a network as well.
Enjoy!  I can tell you after 50 years of dinking with it, Lightning is fun if
ya ain't too close.
Don

Tom Van Baak

--
"The power of accurate observation is commonly called cynicism by those who
have not got it."
-George Bernard Shaw

Dr. Don Latham AJ7LL
Six Mile Systems LLC
17850 Six Mile Road
Huson, MT, 59846
mail:  POBox 404
Frenchtown MT 59834-0404
VOX 406-626-4304
Skype: buffler2
www.lightningforensics.com
www.sixmilesystems.com

I suspect this is quite common. You don't have to get into precise time very deep before you realize that all your timing gear is just pile of environmental sensors in disguise. Before time-nuts began, the first timing guy I met was Doug Hogarth (www.niceties.com) and he was seriously into weather measurement. He later got into the world of ultra-precise weight (mass) measurement. So I guess time-nuts is just a subset of measurement nuts.

A quartz oscillator makes a good thermometer and sometimes a hygrometer and barometer too. An OCXO is a sensitive anemometer (just ask anyone who uses a PWM fan for TBolt temperature control). Quartz also makes an excellent accelerometer, gravimeter, tiltmeter, or even seismometer. An OCXO with EFC is a good voltmeter. Atomic clocks are superb magnetometers. And as Einstein predicted, atomic clocks make good altimeters and speedometers too.

So everything we play with is a sensor. It's no wonder we are preoccupied with environmental sensing. Maybe Time is just what's left over after you shield or attenuate or compensate for everything else.

/tvb

See also:

Quartz Resonators vs Their Environment: Time Base or Sensor?
http://dev.quartzdyne.com/pdfs/quartzresonators.pdf
http://www.paroscientific.com/

Oh man does this bring back memories of 12au7s and loop antennas pre
internet 1970 as I recall. A QST magazine article. I built it and it used a
crt for readout.
There wasn't really a way back then to share the data.
But will say this is quite a nice setup.
Regards
Paul
WB8TSL

On Tue, Jun 24, 2014 at 3:35 PM, Tom Van Baak tvb@leapsecond.com wrote:

This one is/was run by the Neveda Test Site. I don't know if NOAA took
it over. When you get strikes, it give the lat/lon.

At the moment, all is quiet on the western front.

However, I have to say that near real time website is more impressive.

I have been watching the blitzortung system in the US for a few days now
and really like the clean and simple display. Very nicely done.
Also downloaded the information package.
Oddly it does not use any 12AU7s in the design.
Regards
Paul
WB8TSL

On Wed, Jun 25, 2014 at 2:24 AM, nuts nuts@lazygranch.com wrote:

Quite true.

One of my other interests is the ionosphere and propagation. This of course has an effect on GPS and other time related receiving systems. In support of my monitoring and trying to measure such things I monitor on a more or less continuous basis CHU on 7850 KHz. This in itself may not seem that unusual except that I am about 20 miles from the CHU transmitters and I monitor this transmission with the idea of creating a dopplergram of it's signal. As we know, HF radio signals are reflected and refracted by the various layers of the ionosphere. In doing so the signal can exhibit apparent changes in frequency due to the continual movement of these refracting and reflecting layers.

My advantage being so close to the transmitter is that I also receive the ground wave of these signals which are not reflected or refracted in any way. I have a receiver set up which feeds Spectrum lab running in a long integration mode and displaying a very narrow bandwidth of just over 3 and half Hz.

I publish my dopplergrams to a dropbox web page here:

https://www.dropbox.com/sh/9dakbbrrn2ju3hc/TIIKrDY-Iu

usually stored by month

these:

https://www.dropbox.com/sh/9dakbbrrn2ju3hc/AAA7FLx2nZuEZzBayIqyMAUza/20140320

are for April 20 this year. The solid line more or less in the center of the image is the ground wave from the CHU transmitter on 7850 KHz, everything else is the Doppler shifted signal as it has been reflected and refracted by the various continuously moving layers of the ionosphere. You will note that sometimes there is more than one predominate Doppler shifted signal.

Variations in the  more or less solid line in the middle of the images is the result of drift in the local oscillator in my receiver. It is not currently locked to GPS. However, as Tom has suggested it makes a good thermometer as it is a relatively high stability oscillator but temperature variations in my lab show as minor changes in these images. I have in fact done a reasonable calibration and I can tell at glance the approximate temperature of my lab near this radio as well as when the furnace has started in the colder months or when the air conditioner starts in the warmer months.

There is a group in Czech Republic doing something very similar:  http://ok0eu.fud.cz/

They are using their own network of GPS disciplined transmitters on 80M and monitor their signals in a similar fashion. They describe their studies as also studying the effects of gravity waves.

Along the lines of trying to measure and study the ionosphere using these dopplergrams, I have also toyed with the idea of trying to make my own passive sounder. There is a network of ionospheric sounders in the Canadian Arctic called CHAIN - Canadian High Arctic Ionospheric Network. They use GPS receivers to measure characteristics of the ionosphere such as total electron count (TEC) by monitoring phase scintillation of the GPS signals. They are using modified GPS's with high stability reference oscillators.  I don't know yet if any of my GPS receivers would provide any useful data even with a high stability reference but the thought occurs that there might be another way indirect way. DGPS beacons transmit corrections for GPS users and something I stumbled across on another web site suggested that some of this data may be buried within the corrections provided by these DGPS beacons. And it so happens that I have a DGPS nearby which I can receive easily and reliably 24 hours a day but I just haven't got round to doing much more than brainstorming and trying to understand just what I need to do to connect the dots.

For reference, this is the web site and blog posting were I stumbled across the idea of using DGPS correction data:

http://goughlui.com/?p=1071

I have not been able to connect all the dots between all these subject but I am getting there.  At least it is fun and educational trying. After all, it's the journey which is brings the greatest rewards, not the destination.

Cheers, Graham ve3gtc

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Tom Van Baak
Sent: June-24-14 3:35 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Loran, GPS, Lightning, Timing

I suspect this is quite common. You don't have to get into precise time very deep before you realize that all your timing gear is just pile of environmental sensors in disguise. Before time-nuts began, the first timing guy I met was Doug Hogarth (www.niceties.com) and he was seriously into weather measurement. He later got into the world of ultra-precise weight (mass) measurement. So I guess time-nuts is just a subset of measurement nuts.

A quartz oscillator makes a good thermometer and sometimes a hygrometer and barometer too. An OCXO is a sensitive anemometer (just ask anyone who uses a PWM fan for TBolt temperature control). Quartz also makes an excellent accelerometer, gravimeter, tiltmeter, or even seismometer. An OCXO with EFC is a good voltmeter. Atomic clocks are superb magnetometers. And as Einstein predicted, atomic clocks make good altimeters and speedometers too.

So everything we play with is a sensor. It's no wonder we are preoccupied with environmental sensing. Maybe Time is just what's left over after you shield or attenuate or compensate for everything else.

/tvb

See also:

Quartz Resonators vs Their Environment: Time Base or Sensor?
http://dev.quartzdyne.com/pdfs/quartzresonators.pdf
http://www.paroscientific.com/

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