Just wondering if anyone could assist with a Force 180 setup where the SM is constantly disconnecting.
They’re running the latest 4.5.5
It’s a really short link - probably 40M and has good clear LOS.
The next pair in the chain work fine with all similar settings (and this is one of 20+ setups where I’ve used the same units).
The only thing I can think of is the customer has his own links fairly close by and possibly there is a channel interference which is causing the drop - it takes ages to reconnect. 20+mins.
Is there a way to lock the channel and/or MAC? (Something you used to have to do all the time with Ubiquiti or they constantly dropped).
As I’ve been having issues I’ve loaded up the units in cnMaestro, so can possibly make changes from there? First time I’ve used it, looks like a great platform and will have to get my other sites on to it!
Thanks in advance.
spectrum scan? scanned from both ends? Did you find a large enough clear enough channel? Depending on where you are in relation to a radar station, you may have to choose a non DFS channel (remember that only the center channel matters for DFS). Not sure where you are but here there is a lot of 5.8Ghz being used as part of the N+ and AC standards. This means you need to look to 5.7 and 5.2 (5.3 can be an option if your area allows for it).
Things to consider:
Your RSSI should not be above -55, better to aim for -60. on the AP of the link set the auto power control to -60 and the SM will automatically adjust to be as close to this as possible. On the AP, you will need to reduce the TX power to make the SM see the AP at a similar strength. The receivers in these radios are good but overdriving them causes the heartbeat to get missed which causes link drops which can take forever to reconnect due to having to wait for the receiver to become sensitive again. A quick power cycle (hard reboot) will speed this up but it will happen again, better to control your received power to an acceptable level. Focus on quality of the link (SNR) over quantity (power level), you can have a crap signal strength but if you have 40dB SNR you can still pass data at MCS15 (MCS-DS9) without link drops.
Your link does not have to be in any particular direction. going building to building leads to installers trying to be perpendicular to the building faces, which not a bad thing can allow for excessive reflections causing self-interference. An angled link will deflect reflections away from being bounced straight back. A good rule of thumb is to take the antenna’s 3dB angle and double it, this is the minimal angle from perpendicular to the wall that you should consider for the link. This will give you a 6dB roll off on any reflections. This is not as pretty as straight across but is better.
Are you on the wall face, on the roof at the edge or is it set back from the edge?
Placement of the radio/antenna is very important depending on the desired goal. Roof to roof should be set back at least twice the vertical distance the antenna is above the roof edge ledge. This will provide a physical barrier to self-interference caused by reflections and will also significantly reduce interfering signals that are coming from ground level. Avoid placing point to point antennas on the wall unless you are sure that you have a clean spectrum and can control all radios being used by all parties.
AVOID CHANNEL STOMPING! It is way better to find a different channel than to fight with another user for the same channel. Choose the channel based on actual needs, 5.2Ghz passes the same bits/hz as 5.8Ghz, the caveat is that the total tx power is lower in FCC/ISED areas but you do not need a lot of TX power to go 40 meters.
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Hello @Douglas_Generous
Thanks for all that info. I’m afraid that I’m not as much of an expert but trying to gain knowledge as I go along, so some of it went straight over my head!
That said, I did run dubug logs on cnMaestro and there were 2 channels that it was dropping out on so I removed them and reapplied a new template.
It seemed to help a bit, but dropped out again this morning. Currently it’s been up for 11hours which is the longest yet.
I’ve attached the latest debug - can you advise on any of it? Some of the lines are channels again.device_response.txt (1.6 KB)
Thanks in advance
You are getting DFS issues, do not use any channels (frequencies) between 5300 and 5770. Uncheck them.
It is not really a good idea to use the auto chanel selection system. This leads to long wait periods as both radios must scan for a clear channel and if they dont agree, they both try it again.
Minimize your frequency list by unchecking all but the actual frequencies you plan to use. And only the bandwidth needed. Dont use a 40Mhz list if you plan on only using a 20Mhz channel and vice-versa. These are the channel center frequency so remember that a 40Mhz channel centered on 5200 spans from 5180 to 5220.
A good start config is to select only 5200 (5800 also works but 5.8ghz wifi uses this frequency), set tx power (transmitter output power) on the AP side (do not use ePTP, set it to PTP-TDD) in the radio tab so that the other radio does not see power levels more than -65 ( remember negative numbers, closer to 0 means more power) on the AP set the sm power control (subscriber module target receive level to -65. This is important and must not be skipped.
Templates in cnMaestro are great IF you have a working set to build from, do yourself the favor and login to the web interface and make your changes there. Once its working the way you want then make a template in cnMaestro.
Go to the cambium support pages and get the guides from the pmp100 series. This will give you a crash course in basic system understanding that carries to pretty much all radios within the microwave bands.
Some of what I was explaining is more on how to think about the world in radio terms and what you can do about issues that do not get thought about. Things either absorbe signal, reflect signal or can do both given the angle of incident for the radio signal on that surface. Mitigate reflections of your own signal is the one single most beneficial thing you can do to create a stable link. Your own reflected signal can give false radar detections as what your log says its seeing. Hence not using DFS channels.
Not knowing your exact layout and signal path or network requirements, all anyone can give you is basic ideologies to point you into determining what needs to change.
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Thanks a lot for your help @Douglas_Generous.
5.2 isn’t available for some reason? However I’ve fixed it on another higher frequency and selected 2 others as back up and it seems stable so keeping an eye on it.
5.2 may not be available in some countries, it is available forthe US and Canada.
Find a channel that does not have a set of brackets with DFS. Then you wont need alternative channels.
If you must keep to a DFS channel, only check the frequencies required in your SM radio. This will speed up the change over to about 30 seconds rather than scanning for a few minutes.
I would still adjust your AP tx power down so that the SM only sees it as -65 and set the SM power control in the AP to -65 as well. Do not frett if you can not get exactly -65, just try not to blast your other radio. Too much received power can trigger false DFS switching. For reference: a signal of -68 with an SNR of 40 is more than enough to run at MSC15 (DS9) without dropping packets or slowing down. You should see a link test showing over 200Mbps.
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