Author Topic: WHOA! Back up and punt? Or call Time Out?  (Read 1467 times)

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Offline Cutty Sark Sailor

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WHOA! Back up and punt? Or call Time Out?
« on: July 17, 2014, 05:21:39 PM »
With some of the recent questions and discussions, on several forums, about distances, detection, location, etc, I thought I'd go ahead and post the attached pdf, even though it hasn't been error checked etc., and is just a rough draft of initial thoughts... isn't complete... and too long to simply post. We'll complete it, perhaps, with your suggestions.

« Last Edit: July 17, 2014, 06:36:44 PM by Cutty Sark Sailor »
 

Offline DaleReid

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #1 on: July 17, 2014, 10:03:59 PM »
This was very good!

Thanks, it is the kind of thing that many (some?) of us want to know and a little bit about what goes into the system in physics terms.

Not enough equations and Summations and integrals, but pretty darned good.

Anyway, it was very helpful.

In the next release, it might be interesting to give an example of how day vs. night propogation speed of the wave would be dithering the accuracy.  For instance, say the same stroke position, about 450 to 900 km away from a station where all the path is in the dark, vs. daylight.  And at say 30 at my station listening to some storms in the spring down in Arkansas where it is 80 on a nice spring day.  Is it a few feet? a few km?  We always think of speed of transmission being so big compared to the distances we are working with, but on the other hand I remember a book about the early internet that the guy who was being probed figured by pinging, that the path must have been through two geostationary satellites, rather than submarine cable.  And remember the old days when the echo on telephone was noticeable if there was a longer path? 

Not critical to this document, but would firm up the various factors that you are otherwise showing may be variables that would skew the calculations.  Just a thought.

What more are you thinking of adding?  This is a great document and resource, so I hope you keep writing in your style that is very understandable.

Dale
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Offline dfroula

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #2 on: July 17, 2014, 10:14:22 PM »
I remember on calls to/from Hawaii as late as the early 80s the phone company was using half-duplex and "stealing" the silent periods in a phone call to send other conversations with TASI.

In my old days of "Blue Boxing" the telephone network, it was possible to dial in a code digit in the routing of a call to force it to go over satellite or cable. Those were the days! We used to route a call to Tokyo via satellite, then back to a phone in the same room over satellite. Some great delays on those calls!

Don
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... I remember a book about the early internet that the guy who was being probed figured by pinging, that the path must have been through two geostationary satellites, rather than submarine cable.  And remember the old days when the echo on telephone was noticeable if there was a longer path? 
Dale

Offline DaleReid

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #3 on: July 17, 2014, 10:24:44 PM »
Yeah, isn't it amazing what went on.  Now with store and forward and echo elimination, one never really knows what is 'now' and what is a few seconds old.

But it just shows that the speed of light isn't what it used to be for fast.

Clever engineering.  It sort of reminds me of a picture I saw of a tunnel with a huge sliding door being built.  It was to stay open at the beginning of a nuclear detonation to allow signals and light for pictures to be taken, some 900' away.  And it was timed so that the hydraulics slammed it shut just as the blast wave was getting to it, to allow the equipment to survive long enough to  continue to collect data and relay it to the recorders.  I'm sure the calculations on speed of travel of light and blast front at whatever temperature was ambient in the tunnel were all well researched.  And the light pipes for the Ivy Mike detonation were filled with helium to allow faster transmission of light to the detectors rather than use stale old tropic humidity and ocean air.

Who would have thought.

Now we have our little RED boards synched to satellites that give near microsecond accuracy.



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Offline dfroula

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #4 on: July 17, 2014, 10:35:51 PM »
Another trick that was possible with certain tandem switches was to route a call repeatedly on the trunks between two cities (Akron and Canton Ohio, for example). It was possible to "stack" the call between the two cities several dozen times, sometimes tying up all the available direct circuits between the cities. Then, one would route the call to a regular phone. The delays really added up after a few dozen links.

Even if the direct trunks were made busy by the single call, the system could still alternate route other calls through intermediate cities. The old telephone network was quite robust. Ma Bell took a dim view of such experimentation.  :oops:

Don

Offline DaleReid

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #5 on: July 17, 2014, 10:52:47 PM »
Are you old enough to remember the old CrossBar system?  or are you an ESS kid?

The genius behind making rotary phones control line finders and all is more amazing to me than just plain old electronics switching stuff. 

The museum at Milwaukee WI had a demo using an old system showing the last two digits being dialed.  Fascinating machine.

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Offline Cutty Sark Sailor

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #6 on: July 17, 2014, 11:24:59 PM »
Not enough equations and Summations and integrals, .Dale
No, not getting into math and equations, and them quantum thingies... this is hard enough for some of us old fogies to wrap out heads around. Plenty of math etc available... check the references, or just spend some time Googling, or Yahooing, or something. Hard enough to try to simplify without all that stuff...  ](*,) Besides I gave a few specifics on stuff that skewed the calculations... Somebody else has already done that work... I ain't gonna do it again.

Mike
« Last Edit: July 17, 2014, 11:27:48 PM by Cutty Sark Sailor »
 

Offline dfroula

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #7 on: July 18, 2014, 10:26:52 AM »
Heh...I remember Strowger rural telephone switches and motorized Panel central offices! Crossbar is modern stuff!

Don

Are you old enough to remember the old CrossBar system?  or are you an ESS kid?

The genius behind making rotary phones control line finders and all is more amazing to me than just plain old electronics switching stuff. 

The museum at Milwaukee WI had a demo using an old system showing the last two digits being dialed.  Fascinating machine.

Offline Cutty Sark Sailor

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #8 on: July 18, 2014, 11:02:31 AM »
Wow.  I can tell this was a valuable thread... didn't take long for it to be hijacked... ah.... well...
 

Offline dfroula

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #9 on: July 18, 2014, 11:06:20 AM »
 :oops:

Offline JonathanW

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #10 on: July 18, 2014, 11:51:05 AM »
Not at all -- I think it has some good information, esp on TOA/TOGA.  But I take it the goal is a document for advice on system tuning, or at least advice that may help to produce more uniform and better station setup, so it needs to be fleshed out?

A couple things I'd note on the doc so far -- there should be limits on the length of coax, too.  Even though the right coax (75 ohm) won't substantially affect the preamp high pass filter characteristics regardless of length, there are still signal losses, including pre-amp power rail voltage drop, and the concern of locating probes far from GPS-derived station location...

But that's a minor nit.  Obviously, "long coax, short, shielded cat5e" is the name of the game if you need to locate the probes a distance away from the controller...

The second thing is that, I thought the C-channel is the main E-field channel, and the other two are described more as "back-up channels" that are there mainly for less than great listening environments.  Learn something new every day.  Timing, as you say, is critical, though--known channel delay and phase/group delays are important.  We're a community of tech people, including those who like to experiment.  That can lead to unintended consequences.

Oh, and after last weekend, I think I'd add something about attic work and not impaling your head on roofing nails.  But maybe that's for another doc :)
« Last Edit: July 18, 2014, 11:58:56 AM by n0ym »

Offline Cutty Sark Sailor

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #11 on: July 18, 2014, 12:29:05 PM »
Not at all -- I think it has some good information, esp on TOA/TOGA.  But I take it the goal is a document for advice on system tuning, or at least advice that may help to produce more uniform and better station setup, so it needs to be fleshed out?
It's my personal hope that folks will read it, think about it, and come to some conclusions. Yes, I think it needs expansion, but that needs to come from experience and knowledge as server processing changes... all we can go on right now are the basics, and previous experience... conditions will change heading toward cold weather, anyway...
Quote
A couple things I'd note on the doc so far -- there should be limits on the length of coax, too.  Even though the right coax (75 ohm) won't substantially affect the preamp high pass filter characteristics regardless of length, there are still signal losses, including pre-amp power rail voltage drop, and the concern of locating probes far from GPS-derived station location...
  The losses are insignificant as far as the e field signal is concerned... keep in mind that the actual output of the preamp is reduced to something like 1/16th before it actually enters the first amplifier!  Developers at one point were even suggesting up to 3000 feet or so for a max...  turns out the time delay isn't that bad, either, according to Richo et.al. Let's not go into waveguide theory, however... remembering that the actual energy point in a waveguide appears to exceed the speed of light.
Quote
The second thing is that, I thought the C-channel is the main E-field channel, and the other two are described more as "back-up channels" that are there mainly for less than great listening environments.  Timing, as you say, is critical, though.  Learn something new every day.
As far as 'locating'... only need one channel... the TOA... hence on H field, only one channel is used. When attempting to detect strength, polarity, type, etc... must have more data. When we start operating with more refinement, more 'frequency/strength/phase" relationships would be considered... Now, since a lot of this is frequency dependent related to time and phase and 'rise time' especially when dealing with sky waves, that's where the other frequency signals are looked at. Remember, we see something on our signals pages that is totally different the server is looking at. This stuff isn't implemented yet. At any rate, since C contains the 'broadest' frequency strength info, it is used as the 'trigger'... to oversimplify. One reason Dual operation might be best, is because of the broader bandpass of the H amplifier. At one point there was discussion that 'they must be used together'... then they realized E field could be almost, that is almost, as good as using both. One issue with E field is it's extremely sensitive, therefore the range must be restricted in some fashion, for the type of network we're helping create.

 

Offline dfroula

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #12 on: July 18, 2014, 12:31:59 PM »
A few thoughts...

"The TOGA of a sferic is that instant when the regression line of phase versus frequency over a speci9ed band has zero slope."

I'm trying to figure out what this means.

I read it as saying that TOGA at a particular station is when the energy at a certain frequency stops rising and peaks (zero slope).

Sound about right?

Also, what is the velocity delta between day and night for the various frequency bands...might be good to show the table or graph.

My impression from the documentation is that the length of the wire connecting the H-field antennas to the amp is far more critical than the length of the shielded CAT5 connecting the amp to the controller. I imagine this has to do with the impact of the capacitance of the cable delay at the high-impedance amp input is greater than that of the low-impedance amp output.

The same principle applies to the e-field 75 ohm cable run from the preamp to the amp. The very high input impedance at the preamp op-amp has already been converted to a low impedance signal for the 75 ohm cable run, so the additional capacitance of the 75 ohm cable run has negligible delay impact, allowing for long cable runs. That applies also to the shielded CAT5 run from the e-field amp to the controller.

There is also a hysteresis delay associated with the properties of a ferrite antenna that is not present in a wire coil antenna or coaxial loop.

I'm thinking the delays introduced by e-field amp filters are fixed. Therefore, other delay sources will not affect the relative delays between the three e-field amps/filters.

Don
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Offline DaleReid

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #13 on: July 18, 2014, 01:34:46 PM »
Mike,
No this is a GREAT thread, sorry for the, ahem, slight diversion.  Blame it on the hour of the night and neurons firing that hadn't in awhile.

I am glad you did NOT put all those math thingies in there.  While I like to read them on occasion, there is more need for the document you started.  Take us by the hand, lead us down the path safely, and the next time we pass, we can stop to admire a particular flower or plant, even learn it's name or where it grew originally.

But far too many pamphlets or books have blossomed into the ubiquitous derivations and makes the first pass at understanding a bit tough.  I'll take the NOVA approach first, then go to school later.

Keep adding, I don't have the resources nor background you have.

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Offline Cutty Sark Sailor

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #14 on: July 18, 2014, 03:13:41 PM »
Dale, you do have an 'inquiring' mind... just go read stuff... a lot of the info comes from the reference I mentioned at the top of the PDF.... that article is cited in the Blitzortung Project manual, so it's not an obscure publication.... there are other things out there... just search for them.  Now, I don't know exactly how many of the principles the developers are actually using, or planning to use, and I strongly suspect there are some innovative new approaches being applied, or about to be used, that are not presently in literature.  I do know a few things that have been mentioned specifically that I noted, and some is 'suspicion'.

Don, I don't understand the 'regression' to zero slope... I've not studied that, and am not a mathematician... for now, I'm thinking that it's where the different frequencies' phases are 'added' together until they flatten out to either 'zero' or a perfect square wave, with no slope... and that would give a pretty exact time difference from the original first trigger time, which can then be compared  to arrive at a much more precise time of actual stroke.... I'm not sure it works with the 'peak' of any single frequency, but the 'group' of frequencies. If you look at the e field signals, you can see points where the three frequency band signals attempt to get rising or falling edges 'in sync' instead of the initial  phase shifts between them at first reception. I think that might be a hint at what the math is doing, much faster... computing a point where they all level out together.  I need to think back into my old ECM days, but I think some sophisticated tracking radars do something similar...

I don't have access to the Book written by Watt, and could not find a fast reference when I was writing those thoughts. I believe the discussion there refers to 'group velocity' and centers around 'skywaves' rather than ground waves. I think it's referring more to the Ionosphere layers' different thicknesses and altitude day vs. night, and the effect that has on certain frequencies...and which Ionospheric region reflects them. I can see an easy 10 mile+ timing error occurring as the Ionosphere changes in altitude and strength, if we're just triggering on the first pulse's arrival.  Station A gets a ground wave pulse, and station be gets a reflection... over simplified a bit, say the pulse has reflected and travelled an extra 10 miles to get to B.... and arrives considerably later than would be expected if a straight line.
 

Offline SLOweather

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #15 on: July 18, 2014, 03:52:33 PM »
Wow.  I can tell this was a valuable thread... didn't take long for it to be hijacked... ah.... well...

Awww, don't kill the hijack yet... :) The 'jack brought up memories of Captain Crunch (aka John Draper) Blind Joe Engressia, TAP magazine (started by Yippie founder Abbie Hoffman), blue boxes, red boxes, black boxes, using #14 brass washers for dimes... I actually got to talk with Captain Crunch and Joe once in probably early 74.

One of Steve Wozniack's and Steve Jobs' first projects was building a Blue Box. It's on display at on display at the Computer History Museum.



Dfroula will no doubt know how Captain Crunch got his nickname.

Offline dfroula

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #16 on: July 18, 2014, 04:56:00 PM »
(Sorry Mike) I designed and sold/sell a PIC-based blue box and run an Asterisk server that allows Blue Boxing, pretty much like the old days. http://www.projectmf.org - My other hobby...

630-485-2995 for the Blue Box server access.

Don
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Offline SLOweather

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Re: WHOA! Back up and punt? Or call Time Out?
« Reply #17 on: July 18, 2014, 05:33:57 PM »
Ahh, Don, you rock! And I even found an Android Blue Box App!

(Sorry Mike) I designed and sold/sell a PIC-based blue box and run an Asterisk server that allows Blue Boxing, pretty much like the old days. http://www.projectmf.org - My other hobby...

630-485-2995 for the Blue Box server access.

Don
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