As long as each device is really receiving a correct sync pulse it should be fine.
The problem comes from when one gps receiver at a site isn't producing the same pulse as everyone else. It happens far more often than one would expect. Personally, I am nervous whenever anyone says they are using sync from more than one GPS per site at a time, as I've seen even good gps receivers provide a sync pulse which is way off of the correct timing under certain circumstances. That said, most of the time you won't see this issue as long as each receiver is operating correctly and has good geometry to the visible satellites. On Sep 25, 2014 6:00 PM, "Adam Moffett via Af" <af@afmug.com> wrote: > > As far as I know, the PMP450 has the internal antenna, ePMP does not. I > can tell you that without the antenna attached, the one I had on the bench > the other day did not see any sats. > > Jeremy: Yes each GPS Sync ePMP comes with a GPS antenna. It's a magnetic > puck type like you would stick on top of a car, but It goes onto a steel > plate in a pocket on the top of the Cambium sector antenna. You should buy > one of Cambium's sectors and an AP before you consider third party antennas > btw, the cambium one has a couple of convenient features (like the GPS > antenna pocket) that I don't think anybody has duplicated yet. > > They don't all have to see the same satellites. You can use a mix of sync > devices. You can change the sync source remotely via the web GUI if you > have more than one connected. > > It has been asserted (I think by Packetflux) that you could get minute > timing differences if you use two different sync sources at the same site. > I'm not clear on how terrible of a problem that would be, but I know lots > of people end up with a mixed bag of timing sources for one reason or > another. Like when you add that 5th AP but forgot that you only had a 4 > port sync injector. > > > the APs come with an antenna for GPS, but its never been clear to me > whether there is also an internal patch > > On Thu, Sep 25, 2014 at 4:31 PM, Jeremy Grip via Af <af@afmug.com> wrote: > >> So would you be able to switch over to the onboard sync remotely? Do >> you need an antenna for each AP for using it? Do you think it’s as precise >> as using an CMM4 (or SyncPipe Deluxe w/Gig Injector) if not as robust? If >> all POPs are sync’d with same Up/Dn ratio and max cell distance and they’re >> talking to the same birds, is it pretty much the same? >> >> >> >> >> >> *From:* Af [mailto:af-bounces+grip=nbnworks....@afmug.com] *On Behalf Of >> *Adam Moffett via Af >> *Sent:* Thursday, September 25, 2014 2:55 PM >> *To:* af@afmug.com >> *Subject:* Re: [AFMUG] Cambium Newbie Question >> >> >> >> >> >> .....also the PMP100 SyncInjector from Packetflux ought to work with >> ePMP. You might want the gigE version, but in the real world with a mix of >> subscribers at different MCS levels I'm not sure how likely you are to >> exceed 100x100. >> >> The CMM4 is a much more rugged beast. It is expensive, but you are not >> likely to go back and wish you'd bought the cheap one. >> >> My plan is to hook up the internal GPS and have it available, but also to >> provide sync over power. Once you are using GPS sync to re-use channels it >> becomes critical that it's always working, so better to have two timing >> sources available IMO. >> >> They have built in GPS if youre on a budget, not sure why alot of >> people are so die hard against using it >> >> >> >> On Thu, Sep 25, 2014 at 12:56 PM, Jeremy Grip via Af <af@afmug.com> >> wrote: >> >> I’m looking at ePMP w/channel reuse from a cost-comparison standpoint. >> Trying to figure out how much I need to spend on GPS synch for a 4 AP/ 2 >> channel cluster. Does it need to be a CMM4? I will want to be synching >> multiple POPs… >> >> >> >> >> >> Jeremy Grip >> North Branch Networks,LLC >> >> >> >> >> >> >> >> -- >> >> All parts should go together without forcing. You must remember that the >> parts you are reassembling were disassembled by you. Therefore, if you >> can't get them together again, there must be a reason. By all means, do not >> use a hammer. -- IBM maintenance manual, 1925 >> >> >> > > > > -- > All parts should go together without forcing. You must remember that the > parts you are reassembling were disassembled by you. Therefore, if you > can't get them together again, there must be a reason. By all means, do not > use a hammer. -- IBM maintenance manual, 1925 > > >
