Lately sort of discovered the spectral scan tool. I knew it existed but never really took a good look into it, until I found that a normal scan doesn't see a lot and you need to set the scan frequencies in the 'scan' portion of the unit you need the scan off.
What I do now is do a remote (so from the AP's winbox session I open a telnet session to the client) frequency-history. You set the range and some time frame. Let the scan run for instance 30 secs after about another 20secs or so the remote unit returns the results in the telnet winbod. (The telnet session doesn't break, like a winbox session does. A telnet session just waits until unit comes backup, even after 5 mins....)
So, find the IP of the CPE and open under / tools a telnet session (there are other ways to open one but for simplicity this one)
after typing your admin and password the remote unit opens in telnet window (that runs in the AP winbox session)
<enter> the unit opens in the wireless interface menu section,
<enter> and the unit returns with the wireless interfaces and its setting,
spectral-history 0 range=5100-5950 d=30
Now you'll see the CPE disconnect after some time but thats normal. Wait until the CPE connects again and wait about half a minute more (depends on how good the connection to CPE is and how many other CPE's connect to AP)
Now, after this time the still open telnet window (before typing the codes to do the scan widen it to the whole screen, that gives best resolution) shows the spectral scan result in color! Very nice. You probably see a yellow or red color band where your AP is transmitting and all other signals around. Now you can see if your spectrum at the client is really used and if there is anything free you might think to move...
To guarantee that another 3rd party source is not interfering with your AP's working frequency you can switch your AP's radio off for about 20 secs just after the start of the CPE's scan.
In the graph you can now see your AP's spectral usage drop off and come back. If it still shows yellow colors close to your AP's working freq. even when it was off, you know some other frequency is disturbing yours....
The advantage of this spectral scan is that the scan setting in the wireless part of the radio at the CPE can be left as it was. I usually only set the frequency of the AP so the CPE comes back asap after a disconnect. It doesn't have to 'search' in the band for the AP.
Second advantage is that the spectral scan will pickup 'any' frequency (802.11? I actually don't know about non 802.11 radio sources) in the band. 5Ghz, 10, 20 or 40 and with or without shift.
You can do the same in the AP or other CPE's to see if other places are bothered by the same interference sources.
In the AP I also do a scan with 10 and 20Mhz wide channel. It gives me the names of the other networks so I can identify which network is the one that disturbs mine! (I found to my shame at some occasions it was actually one of my own! But ok, I use 50 different radio's!)
Now, one reason why an omnitik is a very good idea to have at your AP: MT 802.11ac can't do the spectral scan!
So, if all your CPE's are also ac than your thrown back to the use of the 'scan' tool in the winbox. That's a lot more complicated to do and doesn't give all the info you want.....
I really don't understand why bringing back the spectral scan tool in ac units again. But I've been told its more a shortcoming of the chipset than the software...
But for me its one reason why I still won't use any ac CPE units. What is the use of ac in PtMP networks if I hardly can 'see' what the spectral situation will be.
ac is partially a solution for spectral issues, but you need a tool to at least use it than to the advantage. Now its not....
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Rudy R. Puister
WISP operator based on MT routerboard & ROS.