damn,,,you went way back to get that tovarich name...cool I love this list
Jaime Solorza Wireless Systems Architect 915-861-1390 On Wed, Aug 12, 2015 at 11:36 AM, Shayne Lebrun <[email protected]> wrote: > Nyet, Tovarich. Superior SOVIET RF works four times as hard as any lazy > capitalist RF, and without exploiting the proletariat photons. > > > > > > > > *From:* Af [mailto:[email protected]] *On Behalf Of *Jaime Solorza > *Sent:* Wednesday, August 12, 2015 1:22 PM > *To:* Animal Farm > *Subject:* Re: [AFMUG] GPS Timing > > > > not to worry Comrade RF is universal > > > Jaime Solorza > > Wireless Systems Architect > > 915-861-1390 > > > > On Wed, Aug 12, 2015 at 9:52 AM, George Skorup <[email protected]> wrote: > > Cambium is using a new receiver on the 450APs that does GPS+GLONASS. I > assume it's from Global-Top, but I haven't opened up a new AP to look. I'm > not real excited about using the Russian signals, but with so many > satellites available, it does acquire lock very fast. Have you thought > about doing the same for your 'Pipes? I think it would be beneficial. > > > > On 8/12/2015 5:34 AM, Forrest Christian (List Account) wrote: > > Ok, if you really want to know, I finally found a (somewhat data) document > which describes this in semi-understandable terms. > > And yes, the real time does fall out of the equations (see watch error - > which is how fast or slow your reference clock is). > > http://www.maa.org/sites/default/files/pdf/cms_upload/Thompson07734.pdf > > What I'm hearing from my GPS module vendor is effectively that since they > don't really have to do any additional work to output a 1PPS signal from a > 3d lock, they feel comfortable in doing so. Adding the complexity of > surveying an location to an useful accuracy and then using that to compute > the time is a lot of additional work with a lot of variability they don't > want to try to deal with without additional demand. I do know that a > while back we tried some shortcuts to get there, but they were not all that > useful. > > > > -forrest > > > > On Tue, Aug 11, 2015 at 12:25 PM, Sean Heskett <[email protected]> wrote: > > the satellites are constantly moving tho and since they are moving faster > in orbit than we are here on earth you need to account for relativity. > knowing where you are doesn't give you enough information to know where > the satellite is and therefore you can't accurately calculate the > relativity offset. once you have 3D lock with 4 satellites you can > accurately calculate the relativity offset and therefore calculate the > accurate time for where you are on earth. > > > > shoulda taken the blue pill ;-) > > > > -Sean > > > > On Tue, Aug 11, 2015 at 12:08 PM, Bill Prince <[email protected]> wrote: > > That's what I thought too. Once one of these little beggars has been > online for a half hour or more, the location should be "set" so to speak. I > would then expect them to hold time sync even with 1 satellite in view. > Knowing that the location is static and unmoving, I would expect that > maintaining time lock would be gravy. > > Sadly, this does not seem to be the case. > > > bp > > <part15sbs{at}gmail{dot}com> > > > > On 8/11/2015 10:48 AM, Chuck McCown wrote: > > Interesting, I guess you need to know where you are to calculate the > delay. Had not considered that. But if you know where you are and have > ephermis data, you should be able to calculate the delay and arrive at a > pretty accurate timing pulse with one satellite. > > > > *From:* Forrest Christian (List Account) <[email protected]> > > *Sent:* Tuesday, August 11, 2015 11:39 AM > > *To:* af <[email protected]> > > *Subject:* Re: [AFMUG] GPS Timing > > > > You need an accurate 3d position to get accurate timing. To have an > accurate 3d position using GPS alone, you need four satellites. Three > only gets you a 2d lock, and less than that you don't get a lock at all. > > There are receivers out there which will survey a position and then use > that position to be able to continue to provide a timing signal if you > subsequently lose lock but still have sats in view. As far as I know, > this type of receiver is not in use in any commercially available timing > product for the cambium radios. In fact I think we've almost all ended up > using the exact same GPS modules, at least for any recently designed > product. > > Some of the earlier products would attempt to preserve the sync signal > across a GPS lock loss with various levels of success. For instance the > cmm micro in early releases provided a wildly incorrect sync pulse even > without a lock. Same with early syncpipes. The CTM has a holdover > timer. And so on. I think most of us have moved away from this in newer > designs. > > On Aug 11, 2015 8:36 AM, "Dan Petermann" <[email protected]> wrote: > > What is the minimum amount of satellites needed for a proper GPS sync > pulse? > > And does that differ across products (CMM, CTM, SyncPipe, etc.)? > > > > > > > > > -- > > *Forrest Christian* *CEO, PacketFlux Technologies, Inc.* > > Tel: 406-449-3345 | Address: 3577 Countryside Road, Helena, MT 59602 > > [email protected] | http://www.packetflux.com > > <http://www.linkedin.com/in/fwchristian> <http://facebook.com/packetflux> > <http://twitter.com/@packetflux> > > > > >
