Time to invest in better GPS/Sync system?

Just looking for some advice on GPS with epmp 3000… should I maybe abandon the internal/puck system and invest in packetflux or cn tower switch?

We have been using packetflux for 14’ish+ years and I don’t have a single bad experience with it or a single failure that I can recall. I even use the syncinjector unit to power non-cambium non-synced devices just because it saves space in the enclosures.

That said, if money was no object then those cambium switches could replace both our packetflux hardware and the Mikrotik switch in the enclosures. That would reduce complexity and space needed ! But they have a lot of very expensive features apparently and I just needs simple GPS sync/power and switching. So way more money than I can justify.

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appreciate the reply, I think I will d the same and stop relying on the built in gps of epmp 3000 radios/puck setup. So is there a packetflux setup that I could power and sync 3-4 epmp 3000 and a couple ptp 550?

How much of an improvement in stability and performance would one see using a packetflux setup?

You need one SyncBox Junior Basic Version - PacketFlux Technologies
This is the GPS receiver/antenna you mount it were it can see the sky/sats. It connects to the syncinjector with cat5/6 ethernet. I normally mount them on the outside of the enclosure or building the enclosure is mounted on. We do not have any mounted more than 15ft off the ground.

One of these for every four radios PowerInjector Plus Cambium-Style Sync - PacketFlux Technologies
They provide CMM5 timing and have a port for plugging the above sync receiver into and then another port for daisy chaining however many of these you need (all done with plain old cat5/6 ethernet cables).

You need power. You can power them via your own DC plant if you have one or other DC power supply of your choice or they sell these (24v and 48v versions. 3000 and PTP550 will run on 48v) 48VDC 2.5A Power Supply for various products - PacketFlux Technologies

You can also get a SiteMonitor Base 3 - Classic Edition - PacketFlux Technologies
It allows you to monitor voltages and sats and power cycle ports. I can’t really say anything about these, I have one but I’ve never got around to playing with it.

I don’t know what you are asking here exactly. GPS sync is a “It works or it doesn’t work” kind of thing. The AP’s onboard GPS needs to be able to track at least 3 sats in order to maintain Sync, being able to track more does not make it work better it just allows you to lose some without losing sync. So an AP tracking 20 sats does not work any better/different or have any better performance than one tracking 3 sats. The stability hit however is the AP tracking 20 sats can lose track of 17 sats and still provide sync while the one with 3 sats can not afford to lose track of a single sat.

There is no difference in the performance of an AP tracking 25 satellites and one tracking 3 all that matters is it can track enough sats to to maintain sync.

So, if your AP’s are not shutting down because they are dropping below 3 sats tracked and losing Sync then using a different Sync solution will not do anything at all for stability or performance. If however you are having AP’s stop transmitting because they are losing GPS Sync then the packetflux or CN Switch should remove that problem entirely.

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I really, really appreciate you comments and information!!

So based on my pic this is working fine? On all my sectors that look like the above picture seem to perform worse where others that look like this…

They Perform better… maybe just coincidence? I had posted once before with a similar pic that showed very little yellow and mostly gray for SNR and others had said that it didnt seem right and should be concerned. I am a bit discouraged… this tower is very rural, we are the only WISP in the area and just cant seem to perform well. I really appreciate your help!

This graph basically shows Signal from each of the Satellites – so yes, with all that green, your GPS signals are fine on this AP. You may potentially have some other different GPS issue, but your signals on this AP are fine.

As others have said - GPS syncing is either locked, or it isn’t. Now, just to be clear, it is possible for an AP with low low signals to be locked, and then later to unlock when signals degrade, or when GPS interference get’s worse… But at any given moment, it’s either locked or not. That is the “binary” part that people are talking about. If an AP is Tracking 16 Satellites in the Green… or if it’s tracking 5 Satellites barely in the Yellow… the point is: if it’s tracking and locked, then it’s tracking and locked - and GPS will work the same either way.

SO - if GPS isn’t unsyncing (ie: if you’re not getting alerts that the GSP is going down) then GPS isn’t your performance issue. It doesn’t matter if you have 12 Sats in the green, or 4 in the yellow… if it’s enough to lock and to stay locked, then that GPS will work just as well as 12 or 14 green.

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What other issues would it be if I am not having alerts going off due to “unlocking”?

I have been getting this in last day or so…

Appreciate your insight!

That means the AP lost communication with that SM and that is most often a problem caused by Interference.

The only way I can see GPS sync being the problem here is if your AP is in fact dropping to less than 3 sats tracked but you have really long “Synchronization Holdoff Time” set. The setting for holdoff allows the AP to continue operating for X number of seconds after it has actually lost sync (tracking less than 3 sats). Cambium has said that when running on hold off the APs can go about 1600 seconds before they slowly drift out of sync with your AP’s and start causing problems with any AP’s that may be on the same or overlapping frequency.

I have seen some here on the forums recommend setting sync hold off to much more than 1600 seconds. If you have done that then it is possible that your AP’s are losing sync but continuing to run until they drift out of sync with GPS and start causing interference problems. Meaning the problem is still noise only it’s from your own APs.

Otherwise your issue is probably just good old fashion 5Ghz interference from other WISPs or WiFi routers or 1000’s of other noisy IOT junk. You can try turning on the Spectrum Analyzer on the AP ( the SA does to seem to run a little better on AP’s than SM’s) and if the client is an AC radio you may try running it there (all though in my experience it is almost completely useless/unreliable on the client radios)


Thank you for your continued insight!! I will try and figure out if there is self interference… not sure where to start with that lol.
Here is the AP SA

Hi lads,

I had the exact same problem, with terrible SNR on GPS. I spoke to my Cambium chap and he sent me a bunch of 3M GPS pucks. My signals are now brilliant on all epmp radios.

You do not need anything but to swap out the original crappy pucks for the 3M ones and you’ll be happy, I promise you.

This AP had no green signal whatsoever this morning. Today I added a 3M puck and now its green for days…

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I am glad to hear that you got that worked out! Where you experiencing really low snr on all sats tracked? or was it GPS sync loss? or both?

I had low snr altogether for GPS. I was using the built in GPS on 3000L and the original puck with the 3000. After adding the 3M version to the 3000L it was great. After adding 3M version to 3000 at was significantly improved.

I cant tell you as a fact if sync was dropping or not but sometimes there was interference from the tower across the valley on same freq causing poor uplink speeds, so I suspect sync was being lost. But, it didnt show GPS sync lost in the logs, which is why I cant tell you for sure. I do have a long hold-off time so maybe that stops sync loss from being shown, although I doubt it.

My gut tells me there were syncing issues with the built-in pucks and so far ive not seen them return.

We use the newer 3M pucks on our 3000Ls since they don’t sync to a Packetflux system. Haven’t had any issues with sync being lost or AP suddenly stops transmitting. We also have the 2nd generation pucks on our APs and they are for backup purposes but we do have one still on a 3000L and its working just fine (read: we haven’t had to go to this site in a year so it hasn’t ben changed). if you have any of the first gen pucks, toss them!

If you just need to sync one radio, then a cnPulse is cheaper, but if you need to sync more than one radio and/or also monitor a tower system, provide analytics (stored on the SiteMon or your MRTG/Cacti/other SNMP system) or need to have some basic automation available, then a Packetflux system is a very affordable solution. One that we happily endorse as we have never been happier

As an avid user of Packetflux devices, you can not go wrong! I both personally and professionally suggest this sync system fully and we use it at all of our towers. We used to use one of several methods for tower monitoring (Modified Paradox security panels, Newmar Power’s Tower Monitor, an in house developed mini-PC with serial devices) and they worked but these are cheap (in comparison) and modular to the point of easy standardization and a jr technician (new hire with 30days experience) can swap them out (haven’t had to yet!). The modules are also forward/backward compatible (firmware updates may be required) so just changing/updating a module means it just works. Plus its DIN rail mountable (Sync-injectors need an additional $10part for rail mounting though they do have threaded holes on the back already).

A base system for us consists of Syncbox Jr, a Cambium Sync-injector and a SiteMon2, though we do have a couple with additional modules (temp and relay combo modules and one site where we added more switched inputs for security loops).
(this is from the Packetflux website where all orders are created and tracked)
Syncbox Jr Basic: $99.95
Sync-Injector Cambium-style: $269.95
SiteMon2: $99.95
one DIN rail adapter: $9.99
Total basic Site: $479.84USD plus shipping (usually $35USD and $15 import duties/UPS charges for a Canadian).

The Sync-injector and SiteMon are dual power source capable (up to 48vDC non regulated, though I would encourage you to power them from a regulated 48v source if powering 48v POE devices) and you can pin each port on the Sync-injector for whatever power pin scheme you need except for the 320 and 430 APs which use a split-pair power configuration, you can use the canopy sync-injector for these two though (Gigabit vs 10/100 POE limitation). The Sync-injector provides the power to the Syncbox Jr and you can daisy-chain many Sync-injectors together and they will all be in sync from one source.

The SiteMon is a web interface that does much more! It provides voltage and current monitoring (need a shunt that at max current provides no more than 100mv, we use 100A/100mv), it has a switch input and a relay (NC/C/NO) output and monitors cabinet temperatures with an onboard temperature sensor. The SiteMon2/3 provides some basic automation based on select events, such as turning a relay on when the temperature in the cabinet is above/below a set point.
There are expansion modules to extend the number of relays, shunts, voltage sense points and switch inputs as well as currently able to directly communicate with MorningStar PV controllers via a special DB9 to serial module (we use Midnite Solar PV controllers which have ethernet built in so don’t use this module).
Also, if you need a special function just drop them an email and they will work with you to either create a module or figure out how to build it with current modules or if its a software issue, new firmware.

To give you an idea of the durability of this hardware, we have equipment from 2009 (old Sync-Pipe) still working just fine though it has had firmware updated (to talk to a Cambium Sync-Injector) and I know of even older hardware still working in the field!


So was this your local cambium dealer or a cambium rep? Did you have to start a ticket?

Thank you for the info @Douglas_Generous, really appreciate your insight and advice!

@riddle @Douglas_Generous

Are the new puck style round? I forgot I had 2 shipped to me by cambium in May of this year… would these be the newest style… part # 120300000230A

the latest version of pucks I received were round but they do not look like the original round ones.
I do not have one handy right now to confirm the number

Sorry late reply man. It was a texhnical rep for my area i believe. They are exact same form factor but are 3M brand.