We're using ePMP 1000s on 90 degree Cambium sectors paired with Force 200 CPEs and are having trouble with links past ~8mi. The SNR drops to ~13 and the customer continually hops between two sectors due to poor signal.
Is there a better solution for a distance like this? We'll be having a new customer who is at 11mi and I'm almost sure they won't work when this guy is having so much trouble.
Your experience sounds substandard to what I have seen myself in the field. Can you provide some more details?
Region of the World?
Band?
Channel Size?
Utilizing GPS Sync?
Frequency Re-use?
What is the RSL for the Downlink and Uplink for one of those ~8 mile shots today?
Is it Line of Sight, near Line of Sight, or Non Line of Sight?
Attached is a screenshot of the Monitor>Wireless section of the CPE.
Region of the World?
US
Band?
5825
Channel Size?
20MHz
Utilizing GPS Sync?
Yes, PacketFlux
Frequency Re-use?
No
What is the RSL for the Downlink and Uplink for one of those ~8 mile shots today?
RSSI Down/Up: -83/-71
SNR Down/Up: 14/26
Is it Line of Sight, near Line of Sight, or Non Line of Sight?
LOS
So this is just back of the napkin math...
The free space path loss for an 8.94 mile shot should be 130.9dB in the 5.8GHz band.
The Force 200 SM has a 24.6dBi gain.
If you were in the peak of the beam and the AP were achieving 36dBm EIRP then you should be able to get a -70.3dBm RSL for the downlink.
36dBm - 130.9dB + 24.6dBi = -70.3dBm
You are only obtaining -84dBm downlink RSL today though. So the question is where did the other 14dB go.
Here are some of the possible places that come to mind. Maybe we can immediately rule some of them out.
-SM is deployed outside of the AP sector's beamwidth
-AP downtilt is not appropriate for the region/terrain
-Transmit power is not turned all of the way up on the AP to obtain 36dBm EIRP
-If it is a 3rd party AP sector antenna maybe it is not delivering the performance that the spec sheet suggests
-Possible bad alignment at the SM
-Possible fresnel zone obstruction
-Defective SM
Since 6dB doubles the distance in RFÂ if you could capture most of that 14 dB then you should have no problems with 11 mile shots.
@Seth Poche wrote:So this is just back of the napkin math...
The free space path loss for an 8.94 mile shot should be 130.9dB in the 5.8GHz band.
The Force 200 SM has a 24.6dBi gain.
If you were in the peak of the beam and the AP were achieving 36dBm EIRP then you should be able to get a -70.3dBm RSL for the downlink.
36dBm - 130.9dB + 24.6dBi = -70.3dBm
You are only obtaining -84dBm downlink RSL today though. So the question is where did the other 14dB go.
Here are some of the possible places that come to mind. Maybe we can immediately rule some of them out.
-SM is deployed outside of the AP sector's beamwidth
-AP downtilt is not appropriate for the region/terrain
-Transmit power is not turned all of the way up on the AP to obtain 36dBm EIRP
-If it is a 3rd party AP sector antenna maybe it is not delivering the performance that the spec sheet suggests
-Possible bad alignment at the SM
-Possible fresnel zone obstruction
-Defective SM
Since 6dB doubles the distance in RF if you could capture most of that 14 dB then you should have no problems with 11 mile shots.
The AP cluster is using Cambium branded 90/120 sectors with full 36dBm EIRP. As far as I can tell, there is no issue with frensel zone obstruction. The SM is indeed in between the North and West sectors (with equal SNR/RSSI on both), but with these antennas performing as 90 degree sectors, I didn't think poor side lobe performance would be a problem. The SM is also dialed in as best as we can get it, with movement in all axes resulting in lower RSSI.
The only thing I can think of would be insufficient downtilt on the AP side. How would I calculate appropriate downtilt for a given AP considering CPE distance and elevation difference?
So just a sidenote, the Force 200 does have some pretty strong sidelobes. It is pretty easy to get stuck on one of those and think that you are on the mainlobe.Â
As far as downtilt calculations LINKPlanner will do this for you. Do you have it setup in LINKPlanner already?
If you need any help email me at seth dot poche at cambiumnetworks.com. I would be happy to help.
Hey Seth,
I do have LinkPlanner set up and I spaced the tilt calculator when I asked that question. I'm hoping it takes into account the 2 degree electrical downtilt of the selected antenna when it spits out a recommendation.
Back to your calculation earlier - LinkPlanner is telling me the maximum EIRP is 30dBm in the 5.2 band: is that true?
So, yes, the EIRP of 5.2 is 30dBm in both the downlink and uplink for the FCC. If you were configured for 5.2 then you would definitely expect to see the results that you are seeing.Â
(You mentioned earlier that you were configured for 5825MHz--5.8GHz, correct? Not 5285MHz--5.2GHz?)
LINKPlanner accounts for the electrical downtilt for the antenna that you are specifying in the project. Some of our older antennas did not have any electrical downtilt. If you chose one of those then it would not account for it. If you select the same antenna that you have installed then it will accurately account for electrical downtilt and give you a tilt recommendation for mechanical alone.
Do you mind sending me the LINKPlanner project?
Thanks,
  Seth
Hello,
As a contribution. Other option you can consider for long distance is ePMP 1000 connectorized with external 3rd antenna, I'm very happy with RF Elements UltraDish TP-550 with ePMP 1000 adaptor v2. We use it in a rural installation and we connect the SMs at 34KM (21M) distance.
hullo seth
im having issues with the link planer coz im used to linkui for ubiquiti
