GPS Sync Problem?

Late July 2015- We ordered four PMP 450 3.65 AP's. They were mounted back to back (With some verticle seperation of course) on two different towers roughly 8 miles apart. 

January 1st 2016 @2:30 A.M.- One of the sectors lost GPS sync for no apparent reason. Reboot did not fix. The only way to get clients to reconnect was to put it into "Generate Sync" mode. I tried updating firmware (13.4, which they are all now on) and had no luck. I started the process of getting the unity replaced under warranty assuming a piece of GPS hardware had gone bad.

January 3rd 2016- I decided to go ahead and try to put the radio back into Auto Sync mode, and low and behold, it acquired a GPS signal and has been fine ever since.

May 1st 2016- A different sector, on a different tower, mysteriously loses GPS sync in the middle of the day and had to be put in "generate sync mode". The other PMP450 on this tower facing the opposite direction is now having issues holding some of our customers with weaker signals, as is to be expected.

May 2nd 2016- Try to re enable GPS sync with no luck. Even if left for 15 minutes the sync pulse source just shows "searching".

May 4th 2016- Try to re enable, same results as the 2nd.

Is there anything else to try? or has this GPS hardware died after 10 months of service...? 

What is your GPS sync source?  CMM4?  UGPS?  What firmware are you running?

Sorry, I see you updated to 13.4 firmware.  Still wondering what the "piece of GPS equipment" you are referring to.

The PMP450 3.65 AP's we ordered came with built in GPS Sync. That's what we've been using to acquire a sync pulse. So we're not using anything external.

Here's a screenshot of an AP that hasn't had any issues with GPS sync. Same equipment.

There was a field notice about a year ago saying that use of the internal GPS was not recommended due to the unreliability of some component in those AP's.  I'm having a hard time finding it.  I know we had issues right out of the box with some working fine and others not working at all.  We started using CMM4's on everything then.  Maybe confirm this with Cambium Support, but I will bet that's the isue.

This is correct.  FSB 0939 was issued March, 2013 discussing this issue.  I also can't find it on the community forum pages, so I have attached it here.

Bottom line is that there are certain installations of the Access Point that will cause sub-optimal signal levels to the internal GPS, resulting in loss of lock or inability to maintain the 1PPS pulse.  In these cases, Cambium recommends using an external source of sync (UGPS, CMM or other).

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That's slightly more than a year ago.  haha  Time flies when we're having fun.  ;-)

Thanks Matt.  I couldn't find it either.  Thanks for posting this.

Perhaps we'll have to get some CMM4 equipment. I just found it odd that we got nearly a year without issue and then all of a sudden out of nowhere there was an issue. 

The radio is installed on the upper railing of a water tower without any trees or other coverage for over half a mile in any direction, in the flattest part of Indiana, so I can't see it having a problem recieving the signal. Just figured a piece of hardware inside had failed, or the software controlling it. 

Can my local(ish) Hardware provider sell me the CMM4 equipment required? Is it similar to the 100 series 900Mhz GPS equipment?

How many AP’s per site? The UGPS may be a more economical solution assuming 2 or less AP’s.

Yah, your Canopy supplier should be able to get you any of the sync options. The CMM4 comes in a few different options - tower mount with and without switch, and a rackmount without switch. I prefer using the indoor rack mount and our own switches for better control and limiting hardware up the tower.

Currently there are two AP's per site, they were put up as sort of a feeler solution. We have a lot of Ubiquiti junk that runs less than optimally and we wanted to test the cost efficiency of this stuff for our particular application.

Unfortunately we are located in a less populated portion of Indiana and finding customers that stick around, and can pay their bills on time, is a daunting task. 

All things considered, some external GPS sync equipment is small potatoes compared to what we spent on the AP's, SM's, and licensing. 

We have two at the top of a 160' water tower. So running cable to our cabinet at the bottom would be less than desirable. Especially considering the water dept. of the town in question has voiced concerns about the amount of things mounted and run already. 

And the other two are on a 140' Tower at our central office. So either solution would work at this site.

The goal is eventually to have 360 degree coverage at both sites (and eventually our other sites if it proves to be cost effective). In order to do so, we need to migrate all customers off of the Ubiquiti stuff to free up bandwidth, but again, cost effectiveness is key.

Yup, that all makes perfect sense. I would go with the rackmount unit. They’re pretty nice. I use them exclusively for CMM’s now.

So, rackmount CMM4's are what I should request from my hardware provider?

-Pardon my ignorance. Indiana is still in the stone ages as far as data transfer goes. lol

Ask for these Cambium part numbers:

1092HH - Rackmount CMM4 (includes rackmount tabs, GPS antenna with mount)
N000000L054A - Meanwell 56 VDC power supply, or equivalent.

Geez, $1,800 per tower is more than we were looking to spend. Internal sync was a serious advantage when we considered these radios. As mentioned, we’re in the middle of nowhere. There aren’t a whole lot of people to make this stuff profitable.

If you plan to upgrade your PMP 450 to PMP 450i is mandatory use an external GPS sync equipment (CMM4 if you have more than 2 AP per tower or uGPS if you have max 2 AP per tower) because PMP 450i has not integrated GPS.

@zack_harkness wrote:
Geez, $1,800 per tower is more than we were looking to spend. Internal sync was a serious advantage when we considered these radios. As mentioned, we're in the middle of nowhere. There aren't a whole lot of people to make this stuff profitable.

If you're in the middle of no where then why do you need GPS sync? Most middle of no where places have plenty of spectrum. Just set the AP to generate it's own sync. If you really need cheap sync, why not check out PacketFlux?

As I mentioned before, the UGPS may be a little more economical for just 2 AP's.

But, Eric makes a good point, maybe you don't need GPS sync.  Maybe you can just make one AP generate sync, and run a cable etween the to share that sync.  Or, with adequate separation, just have them both genrate sync and be done with it.