Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > comp.arch.embedded > #12963
| From | Don Y <this@isnotme.com> |
|---|---|
| Newsgroups | comp.arch.embedded, sci.electronics.design, comp.realtime |
| Subject | Re: Comparing phase of physically distant signals |
| Date | 2013-08-03 18:36 -0700 |
| Organization | Aioe.org NNTP Server |
| Message-ID | <ktkb69$eja$1@speranza.aioe.org> (permalink) |
| References | <kticf7$hg3$1@speranza.aioe.org> <b64l99Fbo0nU1@mid.individual.net> <ktjkf9$qe2$1@speranza.aioe.org> <b654s9Ff331U1@mid.individual.net> |
Cross-posted to 3 groups.
Hi Joerg, >>>> Two ideas come to mind: >>>> 1) two equal length cables to connect the "pulse outputs" >>>> from their respective originating devices to the test gear. >>> >>> Installers will hate this. >> >> Exactly. Imagine point A and point B are on different floors >> in different buildings, etc. "Hey, Tony, head out to the truck >> and fetch the REALLY REALLY REALLY LONG cable set..." >> >> (Then, *deploying* those cables -- even if only for an hour or so) > > No to mention the Motrin they will need for the back pain from > schlepping that cable drum up three flights of stairs. Yes. I know folks who do variations of this with *hundreds* of pounds of cable! (since the cable has to be ruggedized if you want to be able to reuse it, etc.) >>>> 2) two *radios* to do the same thing -- after accounting >>>> for different flight times >>> >>> Installers will love this. But why different flight times? Where is this >>> stuff going to be located? Down a borehole? >> >> If you are measuring at a third point (without knowing its >> distance/ToF from each of the other two points -- cuz you >> have no reference you can rely upon!), then you need to >> know the difference "in time" from the "reference output" >> on each device, *through* the respective radio, through the >> "air" and into the "receiver" -- before it can be applied >> to some bit of test kit. > > If it absolutely has to be done from a separate console at a third point > you can have it measure the ToF automatically in both directions. Or > triangulate. AFAIU you don't need a reference, you can just pick on of > the units as reference. In some cases, yes. The third point ultimately gets tied into everything, though, as it is *the* reference (GrandMaster in PTP parlance). But, if I can measure (test equipment, not *inside* the application) the skew between two distant devices, I can always bring the third device into the equation. >>>> [Though I wonder how hard it is to qualify two different >>>> radios to have the same delay, etc. Far easier to trim >>>> two long lengths of wire to the same length!] >>> >>> Aside from using GPS, WWV or some other reliable transmitter you could >>> have a very stable oscillator on each module. Such as a TCXO. Then you >>> have a transceiver on each. You perform a loopback echo locally, via an >>> RF switch. That gives you the latency of each radio (should be pretty >>> much the same for each module). Now only the path adds in which should >>> normally be reciprocal. >> >> [I don't want this to be a recurring cost. So, the radio is >> a "bag" attached solely for testing/calibration/troubleshooting] > > Then it's even easier because you can have calibrated radios of higher > quality. Why not ditch the third point and have the installer do it > while next to one unit? This doesn't happen during installation. The system self-calibrates. This is only an issue when you are troubleshooting something that *isn't* working. I.e., how do you verify that "time" is correct? How do verify that the local servo loop is tracking the current reference correctly? E.g., is the local clock currently *locked*? Is the loop filter currently configured correctly to track once locked (vs. acquisition)? What sort of jitter is the local loop experiencing? Is the reference seen as drifting? etc. E.g., if the loops are out of sync (phase and/or frequency), the network speaker's output is out of sync with other network speakers (or network video), etc. Or, reproducing at incorrect pitch. Internally, these manifest as buffer underruns or overruns (because the local notion of time differs from the system's notion of time). Is the problem *here*? Or, *there*? You (I) want to be able to nudge the system and see how individual components react to those disturbances to give clues as to what's working and what isn't. >> You still don't know what the difference in the propagation >> (through air) from each transceiver. > > With calibrated radios that's a piece of cake to find out. Pulse-echo. > Or let the whole link oscillate. With calibrate network interconnects, the problem wouldn't exist! :> I'm trying to reduce the complexity of the measurement (verification?) system to *a* device -- preferably something non-esoteric (so folks don't have to buy a special piece of gear to verify proper operation and diagnose problems). >> I.e., if the distance to device 1 is A and the distance to device 2 >> is B, then there will be a difference between the signals arriving >> that corresponds to the difference between A and B. Even after you >> compensate for any differences in the radios themselves. >> >> [The same is true with a single radio at device 1 "received" at >> device 2 -- how much time did the RF signal take to get to device >> 2 cuz it's arrival will occur after device 2's notion of the >> device 1 event with which it is intended to correlate.] >> >> That's the appeal between "two equal lengths of wire" -- the >> delay through each can be made "identical". > > But radio can measure them. How much precision do you need? As I said (elsewhere), I can currently verify performance at the ~100-200ns level "with a scope". [I am trying to improve that by an order of magnitude.] But, that's with stuff sitting on a bench, within arm's reach (physically if not electrically). So, I need a (external) measurement system that gives me at least that level of performance. Without necessitating developing yet another gizmo. [E.g., the 'scope approach is great: set timebase accordingly; trigger off pulse from device 1; monitor pulse from device 2; count graduations on the reticule! This is something that any tech should be able to relate to...]
Back to comp.arch.embedded | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 00:45 -0700
Re: Comparing phase of physically distant signals Jan Panteltje <pNaonStpealmtje@yahoo.com> - 2013-08-03 07:51 +0000
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 09:58 +0100
Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 13:21 +0300
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 12:16 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 11:56 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:17 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 13:41 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 22:46 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 14:57 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 23:09 +0100
Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 13:58 +0300
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 12:30 +0100
Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 16:08 +0300
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 14:22 +0100
Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-03 16:38 +0300
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 10:46 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 10:40 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:04 +0100
Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-04 15:55 +0200
Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-04 19:42 +0300
Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-04 21:08 +0200
Re: Comparing phase of physically distant signals upsidedown@downunder.com - 2013-08-05 15:28 +0300
Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-05 22:17 +0200
Re: Comparing phase of physically distant signals Richard Damon <Richard@Damon-Family.org> - 2013-08-05 23:20 -0400
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 14:26 +0100
Re: Comparing phase of physically distant signals George Neuner <gneuner2@comcast.net> - 2013-08-03 14:47 -0400
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 08:17 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:08 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:37 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:57 -0700
Re: Comparing phase of physically distant signals Hans-Bernhard Bröker <HBBroeker@t-online.de> - 2013-08-04 15:58 +0200
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 12:44 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 18:36 -0700
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-04 09:56 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-05 14:53 -0700
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-05 15:38 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 01:25 -0700
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-07 08:06 -0700
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-07 09:21 -0700
Re: Comparing phase of physically distant signals josephkk <joseph_barrett@sbcglobal.net> - 2013-08-03 15:40 +0000
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 10:05 -0700
Re: Comparing phase of physically distant signals John S <Sophi.2@invalid.org> - 2013-08-03 12:13 -0500
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 10:26 -0700
Re: Comparing phase of physically distant signals John S <Sophi.2@invalid.org> - 2013-08-03 12:51 -0500
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 11:54 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-03 20:27 +0100
Re: Comparing phase of physically distant signals George Neuner <gneuner2@comcast.net> - 2013-08-05 03:26 -0400
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-05 10:34 +0100
Re: Comparing phase of physically distant signals Richard Damon <Richard@Damon-Family.org> - 2013-08-05 23:29 -0400
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 08:53 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:49 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:34 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 12:18 -0700
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 12:52 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 13:21 -0700
Re: Comparing phase of physically distant signals Jeff Liebermann <jeffl@cruzio.com> - 2013-08-03 13:31 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-03 14:46 -0700
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 15:03 -0700
Re: Comparing phase of physically distant signals Jeff Liebermann <jeffl@cruzio.com> - 2013-08-03 17:25 -0700
Re: Comparing phase of physically distant signals Joerg <invalid@invalid.invalid> - 2013-08-03 14:50 -0700
Re: Comparing phase of physically distant signals "Paul E. Bennett" <Paul_E.Bennett@topmail.co.uk> - 2013-08-04 11:06 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-04 12:19 -0700
Re: Comparing phase of physically distant signals John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> - 2013-08-03 11:47 -0700
Re: Comparing phase of physically distant signals Richard Damon <Richard@Damon-Family.org> - 2013-08-03 18:23 -0400
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-05 16:53 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-05 13:19 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 00:27 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-05 20:09 -0700
Re: Comparing phase of physically distant signals Paul Rubin <no.email@nospam.invalid> - 2013-08-05 22:12 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 09:12 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 01:47 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 10:08 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:25 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:48 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 10:49 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 03:06 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 11:57 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 10:28 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 21:52 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 01:34 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-07 09:46 +0100
Re: Comparing phase of physically distant signals Les Cargill <lcargill99@comcast.com> - 2013-08-06 07:22 -0500
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 10:42 -0700
Re: Comparing phase of physically distant signals Les Cargill <lcargill99@comcast.com> - 2013-08-06 23:04 -0500
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 23:50 -0700
Re: Comparing phase of physically distant signals Les Cargill <lcargill99@comcast.com> - 2013-08-07 13:05 -0500
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 18:22 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-08 09:35 +0100
Re: Comparing phase of physically distant signals Paul Rubin <no.email@nospam.invalid> - 2013-08-06 22:18 -0700
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-07 03:09 -0700
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-07 12:39 +0100
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-07 13:18 +0100
Re: Comparing phase of physically distant signals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-06 09:23 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:02 -0700
Re: Comparing phase of physically distant signals "Paul E. Bennett" <Paul_E.Bennett@topmail.co.uk> - 2013-08-06 09:49 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-06 02:17 -0700
Re: Comparing phase of physically distant signals Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-08-16 21:07 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-16 14:50 -0700
Re: Comparing phase of physically distant signals Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-08-18 19:55 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-19 11:43 -0700
Re: Comparing phase of physically distant signals Paul E Bennett <Paul_E.Bennett@topmail.co.uk> - 2013-08-20 21:43 +0100
Re: Comparing phase of physically distant signals Don Y <this@isnotme.com> - 2013-08-20 14:49 -0700
csiph-web