ePMP and GPS source

We are a relatively new ePMP user and have quesstions about GPS sync.  We have been using the provided GPS external pucks that are inclused with the AP's and for the most part they work fine.  They have been getting sync while burning them in at the office with a roof to the sky and MOSTLY as we put them on towers.  

However, we have now had 3 or more of them (on different towers) stop receiving GPS signal which of course then causes all of the clients to disassociate!  Many of them up for month's before the issue, but a couple within a few weeks.  We know the radios have a patch antenna inside of them, bu this is really not a solutions for us as we are using KP antennas and they provide a metal enclosure housing to protect the AP's.  

We are beginning to think that using CMM3 or CMM4 will provide more reliable options going forward, but of course it adds another layer of cost.  Also seems like you need to pick one or the other as I have seen posts ablout them not providing similar timing between them.  

Looking for suggestions here and what people are using for their sync sources?  Would of course want to maintain the Gigabit Ethernet connection between radio and switch as well.

We have not yet been able to climb the towers affected to see what the root cause might be and if replacing the puck brings them back.  That too will get to be a costly fix.


Cambium will tell you to use a CMM, since obviously it's ther own product.


This: http://store.packetflux.com/powerinjector-plus-sync-gigabit-version/

And this: http://store.packetflux.com/syncbox-junior-basic-version/

are very cost effective.

Even if we consider the Cambium solution there is still the CMM3 / CMM4 which I cannot really see why we might choose one over the other. 

Can the Packetflux solution be used for only providing the GPS sync and not power?  We are using Netonix switches at all of the sites for powering the devices so the power feature is not really needed.  


Hello Larry,

I'm including couple of threads regarding this topic.



- Make sure GPS firmware version is latest

- If running SW version 3.X, they were affected by a high CPU utilization SNMP issue which was affecting GPS Sync performance. This was fixed in SW version 3.3

- GPS antenna reposition may help

- Increasing the Synchronization Holdoff timer (default is 30secs) may help preventing SM disconnects, if the GPS sync loss  are short in time



Thanks for the information, we are running 3.4.1 and all GPS firmware at the latest.  I do not think the SNMP bug is 100% fixed though as we see CPU utilization spikes still with the current firmware.  Could be something else causing it, but that is for another day.  

Have not been able to get on tower for repositioning / evaluation yet.

We already had the holdoff at 86400 (1 day) to overcome potential glitches as well.  

I did note from one of the posts that all of our pucks are horizontal instead of vertical.  But this is for all 40+ AP's and only a few having issues.  

Still looking for a more reliable solution.  Thanks!