ePMP 3000L - near constant DFS

After some advice please.
New site & new to Cambium.
We have a ePMP3000L with just one F300-16 client which is facing near constant DFS hits.
Firmware is on 4.5.6 on both AP & SM.
RF Elements 30 degree sector. Not near an airport & have selected 3 20 MHz Frequencies with little interference.

Have set the target RSSI for the SM to -65 but it is pretty much constantly down due to DFS.

Any suggestions gratefully received if I need to supply any further info just let me know.


Hi. Have you tried the latest 4.6.1 Release Candidate? It’s technically listed as Beta2, but it’s a LONG ways from being any sort of ‘early beta’. It’s actually expected to become the 4.6.1 in a week or so, so if it was me, I’d give this a try just to see if it makes any difference. We are running 4.6.1 everywhere, and it’s resolved most firmware issues which we are aware of.


That being said - I don’t think that ‘near constant DFS’ is a symptom of any 4.5.6 bug, but if it was me, updating to the latest/greatest Firmware is the first thing I’d do, and then I’d work on it issue from there. :slight_smile:


Thank you for the advice. I have now rolled out 4.6.1-RC26 to the AP & SM. Will be monitoring & will report back. If anybody else has some further tips then please let me know.

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DFS hits are only in DFS channels, have you tried a non-DFS channel? Also, if you are not careful with sector antenna placement you can DFS yourself. All antennas have a rear null location, this varies with each antenna but is usually about 4ft behind the antenna but some antennas have larger rear distance requirements. RF Elements is usually between 3 and 5ft which means your rear separation needs to be more than 5ft between backs of any antenna. Also consider your PTP link if any and any other radio transmitters near this location.

Frame ratio and sync settings must be identical for all sectors that are able to hear any other AP. The rear null will provide some isolation but not enough to be able to ignore this. Also consider any forward sources. Airports are good indicators but how about weather radar stations? Do you know where they are in your area? Military radar applications? Every military aircraft has active radar that can cause DFS issues.

Personally, I would take a noisier channel over a DFS option unless it was for a very short and direct link that I could get 99.9999% assurance that it would not DFS on me.

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Thank you, some very good advice there & some valid points with regards to proximity to other radios at the site which I think is probably the issue. I’m hoping to get to the site in the next few days to move the RF Elements sector away from it’s current position.

Unfortunately the hits are still rolling in with the RC firmware :frowning:

Run a spectrum scan from the AP, leave it run for about an hour. Run it again during a DFS event if you didnt get one during your previous scan. Use fine scan mode, takes longer but is way more detailed.

Look for a wide and reasonably strong rf block. This is either a misconfigured SM (depending on actual distances, you may need to go as low as -70 atpc)

If you leave the scan long enough it will show you any decipherable ssids and it will lable the rf blocks that trigger DFS. Most of us just dont leave it long enough to perform this.

Best thing you can do is switch frequencies to a non dfs channel.

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No non DFS channels available for selection on the radio.
Performing Spectrum Scans not a lot of interfernace at all.

No DFS channels:
Depending on where you are in the world, you may need a country specific key to unlock country specific frequencies. This can be done through the licensing page at: Licensing / Cambium Networks Support

DFS on clean spectrum:
Run the Spectrum scan and watch it carefully. You may need to set your auto refresh to 2seconds in the config-system page. You are looking for a random high powered and wide spike. It may only be 50mhz wide but thats what your looking for. The only thing you can do to mitigate it is to have the AP secondary channels set to be as far apart from each other as you can make them, make sure the SMs have all three channels added to the scan table and remove all other channels from the scan table. This will greatly speed up the recovery time.

Curious thought: are you 100% sure its DFS?
Similar behavior is also from the GPS system, we found that not having an external antenna on the e3k-L causes problems with sync loss. Adding a gps puck solves this with the 4.6.1 RC releases (so far anyway!). I highly suggest either the square Talgos or the new round one p/n: 120300000230a. I prefer the square Talgos as it is a very well performing puck, but it is also not good for rejecting LTE signals which is what the new one does. The Talgos is meant for a vertical surface but works on a horizontal surface and the new round one is for a horizontal surface with a noticeable degradation when mounted on a vertical surface but not so much as to loose sync from.

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Thanks for your continued suggestions and support.

License for GB set, no NON DFS channels available.
3 frequnecies all apart.
Spectrum analysis done; not overlapping anywhere
NO GPS Puck installed!?

setting the country is one thing but also check the license page for a country EU/ETSI country specific license. This opens up country specific frequencies. Follow the link I posted and it will help you.

GPS on the e3k-L is best supplied by the GPS puck. You may have bought yours before they started sending one in the box, contact your distributor and get one. you can also use pucks from any other AP just to get a good GPS source.

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If you are running 4.6.1 software (4.6.1-RC27 with all the fixes) then in the Monitor GPS screen, there is an easy graphical display of the GPS Satellite SNR, as well as an indication if it’s using internal or external antenna. So, that can really help pinpoint if you’re having any GPS issues.

My feeling is that if you’re seeing DFS hits being reported, then it’s likely not a GPS issue in my mind… but a good way to check is to make sure you’re on the 4.6.1-RC27 latest Release Candidate, and have a look at your Monitor → GPS

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