We don't need any stinkin' commie RF!
Добрий День товарищ!
On Wed, Aug 12, 2015 at 12:36 PM, Shayne Lebrun
<[email protected] <mailto:[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]
<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 <tel:915-861-1390>
On Wed, Aug 12, 2015 at 9:52 AM, George Skorup
<[email protected] <mailto:[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] <mailto:[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] <mailto:[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)
<mailto:[email protected]>
*Sent:*Tuesday, August 11, 2015 11:39 AM
*To:*af <mailto:[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] <mailto:[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 <tel:406-449-3345> | Address:
3577 Countryside Road, Helena, MT 59602
[email protected] <mailto:[email protected]> |
http://www.packetflux.com
<http://www.linkedin.com/in/fwchristian>
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