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lap
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radar detected problems

Thu Jul 20, 2017 10:48 pm

I am using hAP ac lite tower for the last few months. Wireless is set to 5GHz only if that matters. Both RouterOS and the firmware are the latest versions as of now (6.39.2 and 3.36). Starting several days ago, several times per day the router started disconnecting all clients, and on all occasions the log showed:
wlan2: radar detected on [frequency]
This causes a lot of connectivity interruptions as the wireless clients are only able to connect after about 2 minutes, which kind of defeats the purpose of having advanced router.
I am probably 10 km away from the closest airport, so I am not sure what kind of radar is detected.
From what I have read here, the radar detection can not be disabled and disconnecting the clients when a radar is detected is expected, but is there any workaround to avoid or reduce these false positives?
 
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Re: radar detected problems

Fri Jul 21, 2017 8:02 am

In this video, Ron Touw explains why this happens, and what to do to minimize it: https://www.youtube.com/watch?v=ZbrbRUAfpac
 
pe1chl
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Re: radar detected problems

Fri Jul 21, 2017 12:09 pm

Well, it has a lot of talk about why it is and why you should not disable it, but I have not been able to locate any secret info on how to make it workable.
Maybe you can point at it, the video is quite lengthy and verbose.

In our installations at high altitude above ground level, I have so far been unable to make DFS work on MikroTik with recent RouterOS versions.
Continuous hopping between frequencies, never staying on a single frequency longer than 5-30 minutes, then radar detected again.
Not usable because after every hop there is some downtime while the unit is again looking for a clear frequency.
On Ubiquiti equipment at similar locations it works OK.

Hopefully this will sometime be fixed so we can again operate according to regulations.
 
lap
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Re: radar detected problems

Sat Jul 22, 2017 8:27 am

In this video, Ron Touw explains why this happens, and what to do to minimize it: https://www.youtube.com/watch?v=ZbrbRUAfpac
Thanks for the link, it explains nicely the reasoning for radar detection. However the recommendations seem to be for WISPs and not home users. Moreover the frequency at which the router (possibly incorrectly) detected a radar is nowhere near the range mentioned in the talk. So the question remains - is there anything that I can do?
 
pe1chl
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Re: radar detected problems

Sat Jul 22, 2017 11:29 am

You already tried setting it to different initial frequencies? It could happen that radar is not detected on all frequencies but
only on some of them. When you can work out which frequencies are not affected (by running it for a while and collecting
the affected frequencies from the log), you might be able to setup a scan list (wireless->channels and scan list in the interface)
to use only unaffected channels.

However, when your situation is like mine: radar detected on ALL channels after some time, even on channels where there
definately is no radar, the only way to work around is is to turn off DFS as long as it is still possible, despite what Ron Touw says.

I hope this problem will be fixed in a firmware update, but as far as I know MikroTik is still in the state of denial about this issue.
 
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Re: radar detected problems

Sat Jul 22, 2017 12:17 pm

I have a client to whom I have built wireles solution with APs from Mikrotik. With new RouterOS versions it was not possible to make a setup that works. The company is in a hall next to which is a tower full of apartments and so many wireless networks.
Mikrotik AOsalways detects radars and trying to change the frequency of high times downtime making my client to go crazy. Even when it works chosen channels are busiest.

I had to downgrade to a version where I can stop DFS.

I have several customers who have installed Mikrotik routers and are working perfectly, but I can not offer them a wireless solution from Mikrotik because of these problems.
 
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Re: radar detected problems

Sat Jul 22, 2017 5:02 pm

False positives are really a big issue with current version of software ?
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Re: radar detected problems

Sat Jul 22, 2017 6:02 pm

False positives are really a big issue with current version of software ?
For me, they are. But they have always been, but in the past you could more easily turn off DFS and not be bothered by it.
In the current version this is still possible but you have to know how.
I am fully prepared to use DFS as a radar avoidance method, but not as a frequency-hopping-for-no-reason function.
So the false positives really have to be eliminated.
 
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Re: radar detected problems

Sat Jul 22, 2017 6:41 pm

I totally agree and when signals from co location AP's at a site start this "Radar Detected" nonsense and frequency hopping like crazy - is nuts?
How do you disable ?
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Re: radar detected problems

Mon Jul 24, 2017 8:02 am

I have also the same problem of radar detection message on my wlan card and unable to connect my client. Any configuration on Mikrotik router to disable DFS feature? Thanks.
 
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Re: radar detected problems

Mon Jul 24, 2017 10:08 am

Please tell me what kind of wireless clients are connected when this happens? Or even nearby. Specifically smartphones and their exact models.

We have already fixed a similar issue caused by the iPhone 6s, but we have observed this with a different brand as well, just want to confirm first, before I say which one.
*) wireless - fixed false positive DFS radar detection caused by iPhone 6s devices;
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Re: radar detected problems

Mon Jul 24, 2017 11:45 am

It happens even without any client connected!
And with no smartphones in the neighborhood.
We have access points in broadcast towers and mobile base station masts and they are unstable even without any connection.
On other very similar sites we use Ubiquiti access points without any issue.
On 2 of the sites where the MikroTik AP's cannot work, we also have Ubiquiti PtP links (Airgrid M5, Powerbeam M5) also no issue.
 
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Re: radar detected problems

Mon Jul 24, 2017 11:55 am

If there is no wifi client around, it might as well be actual radar.
RouterOS will not detect radar without reason, but some smartphones do send out strange signals that RouterOS interpreted as radar in the case of iPhone 6s.

You don't have to be near the radar. Weather radar has range even above 250KM!
The detection mostly applies to Weather radars, not airport radars.
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Re: radar detected problems

Mon Jul 24, 2017 12:08 pm

I know that, but I also know the frequency of the weather radar and we have already been warned to stay away from there.
The problem is that on a 45m mobile base station or a 220m broadcast tower there is not a single frequency where a MikroTik
router will stay for more than a few minutes before hopping to another channel.
In my opinion, it is just mis-detectiong radar due to one of the following:
- it actually receives a radar on a single frequency but due to receiver overloading it "sees" it on all channels
- it receives something else than radar, e.g. the local mobile station (GSM/UMTS/4G) which is on a different frequency band but still affects the receiver

During another experiment I saw that there is quite strong breakthrough of image frequencies in the MikroTik AP's.
E.g. we have locations where 4 AP's are connected to 4 sector antennas facing outwards and placed about 6 meters apart,
when 3 of them are operational and one is doing a scan, I see the other 3 at different channels than where they are transmitting,
much weaker of course but still well detectable. (it looks like 2*IF images)

When the same happens to radar, it will render even more channels unusable due to radar detection.
 
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Re: radar detected problems

Mon Jul 24, 2017 12:27 pm

That is certainly not normal. Please contact support with the files and all the details.
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Re: radar detected problems

Mon Jul 24, 2017 2:48 pm

Shouldn't be the weather radar detected by special pattern it transmits? This pattern should be positively recognised by the radio. If not then no radar detected result is the only acceptable output. Definitely no false positive detection can occur... Is that so?
 
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Re: radar detected problems

Mon Jul 24, 2017 6:00 pm

Shouldn't be the weather radar detected by special pattern it transmits? This pattern should be positively recognised by the radio. If not then no radar detected result is the only acceptable output. Definitely no false positive detection can occur... Is that so?
Ideally yes but all bets are off when as mentioned by pe1chl "...due to receiver overloading it "sees" it on all channels ..... " I would go further by saying it wouldn't take a radar signal to trigger this frequency hopping endless cycle?
 
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Re: radar detected problems

Mon Jul 24, 2017 8:12 pm

Sure. But I meant the case when other devices can fool the routerboards. Seeing the same things on wrong frequencies during background scan always looked for me like an error in some code loop rather than physical radio problem.
 
lap
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Re: radar detected problems

Mon Jul 24, 2017 10:41 pm

Please tell me what kind of wireless clients are connected when this happens? Or even nearby. Specifically smartphones and their exact models.

We have already fixed a similar issue caused by the iPhone 6s, but we have observed this with a different brand as well, just want to confirm first, before I say which one.
*) wireless - fixed false positive DFS radar detection caused by iPhone 6s devices;
In my case the device connected was a MacBook Pro. Not sure about the nearby devices as the problem that I am having is with a home router (hap ac lite tower) is in a residential area with a lot of unknown wireless devices around.
 
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Re: radar detected problems

Tue Jul 25, 2017 9:18 am

Shouldn't be the weather radar detected by special pattern it transmits? This pattern should be positively recognised by the radio. If not then no radar detected result is the only acceptable output. Definitely no false positive detection can occur... Is that so?
Yes, there is a pattern. And for some crazy reason, when Apple updated iOS, the iPhone 6s model started to emit the same pattern when connecting to a MikroTik AP. This only happened after the iPhone 6s was updated to a newer iOS update. It was not a RouterOS detection bug. We are now seeing a similar issue with the Google Pixel devices, but that is still being investigated in more detail. That radar pattern is apparently too short and can sometimes be found in other signals.
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Re: radar detected problems

Tue Jul 25, 2017 10:40 am

Is there a way to turn on more detailed logging to see what pattern it is seeing as a reason for channel change and how long it is present?
Or a way to log "detected radar" events when DFS is off? So we can collect info on the running devices without rendering them unusable?
 
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Re: radar detected problems

Sun Aug 13, 2017 9:57 pm

When selecting the frequency starting "search for radars" it takes 1 minute for 20MHz and Ce 40Mhz.
The Ceee 80MHz takes up to 10 minutes.
Is this expected behavior?
 
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Re: radar detected problems

Sun Aug 13, 2017 10:21 pm

It depends on the frequency. Maybe your 80 MHz channel includes a frequency where 10 minutes of checking is required. Check your local regulations.
 
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Re: radar detected problems

Tue Aug 22, 2017 7:45 pm

Hello.

I have similar problem with my Samsung Galaxy A5 2016 running on Android 7.0. If I try to connect it to 5 GHz wifi (I have MikroTik hAP ac), it disconnects my second client (notebook lenovo W520) and I see in log radar detected on 5580000. And the frequency is sometimes changeing (5540000, 5300000, 5660000). I have RouterOS 6.40.1.

It runs OK on 2,4 GHz.
 
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Re: radar detected problems

Thu Sep 07, 2017 12:26 pm

Because of ongoing false positives of "Radar Detected" generated by either co-location or/including nearby/distant other operators AP's, moving frequency and replacing AP's with "reduced co-location Interference suppression" sometimes only increases the time between the false positives and re positioning AP's is not a option, we have had no choice but to downgrade and lose wireless improvements available on the latest versions.
 
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Re: radar detected problems

Thu Oct 05, 2017 11:59 am

Avoiding to open new discussions.....
I've been using Alvarion radio for a link (3km) with DFS enabled for several years. It correctly detects radar and founds free frequencies.
After a storm I had to replace Alvarion using a Routerboard (AP and client are RB433 with ROs 6.19): DFS detects radar on all frequencies so I can't find available frequency. (I'm using dame panel antenna for all devices)
As backup I tested Ubiquiti, it correctly detects radar but it still finds free frequencies (the same frequencies used by Alvarion).
Why can't I get free frequencies using Routerboard?
Any idea?
Thanks.
 
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Re: radar detected problems

Thu Oct 05, 2017 12:43 pm

6.19 is quite outdated. Maybe actual version can behave in other ways...
 
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Re: radar detected problems

Thu Oct 05, 2017 5:55 pm

Just updated to V6.40.4 on some AP's, time will tell if its stable?
 
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Re: radar detected problems

Wed Nov 01, 2017 9:52 am

... And what the time told you so far?
 
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Re: radar detected problems

Wed Nov 01, 2017 12:22 pm

... And what the time told you so far?
I had to roll back to dfs on/off version to ensure no disruptions of service for customers, the AP's that are currently running 6.40.4 were the ones that did not give problems , so I desided to leave them ,checking an ap on a test circuit is really of no use in this senario.
 
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Re: radar detected problems

Wed Nov 01, 2017 1:40 pm

It is really pitty that mikrotik forces the DFS where it is not necessary. But anyway, haven't you tried the superchannel mode? It should be without DFS if I remember well - but haven't tested recent versions for that,so it is just an assumption.
 
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Re: radar detected problems

Wed Nov 01, 2017 1:59 pm

It is really pitty that mikrotik forces the DFS where it is not necessary. But anyway, haven't you tried the superchannel mode? It should be without DFS if I remember well - but haven't tested recent versions for that,so it is just an assumption.
Just tested and on superchannel mode freq=5600 - test client re-established wireless connection in less than a minute rather than 10 mins that it usually takes in DFS mode? :) :)
 
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Re: radar detected problems

Wed Nov 01, 2017 3:58 pm

It is really pitty that mikrotik forces the DFS where it is not necessary.
That's not true. If you are in an area (Country) where this is not necessary, you are free to use the Superchannel wireless mode, and lower 5GHz frequencies (5180-5240) and there will be no radar detection at all.
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Re: radar detected problems

Wed Nov 01, 2017 4:36 pm

I meant when we use the country regulatory domain setting and we know what weather radars on what frequencies and at which azimuth are in use, it does not make any sense to force DFS on other frequencies or at places or orientations that are fully out of radar reach. Actually false positives are making our links unusable many times so we need to step out of the setting to the superchannel or use older ros versions where DFS was optional parameter.
 
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Re: radar detected problems

Wed Nov 01, 2017 4:44 pm

It is really pitty that mikrotik forces the DFS where it is not necessary.
That's not true. If you are in an area (Country) where this is not necessary, you are free to use the Superchannel wireless mode, and lower 5GHz frequencies (5180-5240) and there will be no radar detection at all.
It also a pity we have to learn wireless tweaks from non Mikrotik support staff - Example Radar Detect and DFS on MikroTik https://www.youtube.com/watch?v=ZbrbRUAfpac (Slide 55)
I will quickly add that the presentation was professional and very informative but my point is simply that Mikrotik as wireless vendors, etc should have in house staff doing this type of
presentation unless ????
 
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Re: radar detected problems

Wed Nov 01, 2017 4:56 pm

Note that in some countries the sale of equipment that can operate without compliance to the local regulations is not allowed, and so it is not always possible to officially document (hidden) features that allow such operation.
In fact, talking too much about it might lead to the removal of the feature, similar to current regulations in the USA where it is no longer possible to tune the radio out of the allowed band (in a model sold in the USA).
 
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Re: radar detected problems

Thu Nov 02, 2017 1:17 pm

a manufacturer can't just recomment "great ways to break the law". The standard and the law sets these rules, often they have to be followed, even if you think you know there are no radars.
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Re: radar detected problems

Thu Nov 02, 2017 1:23 pm

Yep. Unfortunately this is true.
 
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Re: radar detected problems

Mon Jan 22, 2018 1:41 pm

Hi Anyone resolved problem with DFS? There is any option to disable DFS or bypass? Could I setup different country and this way could I disable DFS?
Somebody already bypass DFS? I have huge problem with !DFS!
What it is a different between radar detected and running app info on the bottom on wireless window?
Thanks for help :D
 
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Re: radar detected problems

Thu May 17, 2018 11:58 am

After forcing us to new Router OS versions higher then 6.36.3, due to Mikrotik virus affecting the older versions, all bought Mikrotik WiFi hardware became pieces of unusable plastic boxes, usable maximum as toy for dog... Really "funny", but it cost lots of money and finacial lost due loss of customers! ! Will Mikrotik return money for such devices, where is not possible switch off DFS or avoid OS drop by virus infection in same time... ???
Or does exist alternative version of current mikrotik OS, where is possible to switch DFS OFF ? E.g. thru hidden command in terminal window?
 
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Re: radar detected problems

Thu May 17, 2018 12:06 pm

I would rather hope that the DFS problem is fixed. False DFS radar detection is a big problem in MikroTik equipment, when using
Ubiquiti equipment the same problem does not occur. That has nothing to do with regulations and laws, it is a matter of fixing
the software that does the false DFS radar detects.
 
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Re: radar detected problems

Fri May 18, 2018 2:31 am

I can imagine it is not that easy to fix something unless you can precisely replicate the issue. DFS is required by certain countries on certain frequencies. I hope mikrotik implemented those correctly so if you select for example country=united states , then DFS should be disabled on 5180-5240 and 5745-5825 . If manufacturer allows you to disable DFS on frequencies which require DFS, their device will get not approved, thus becoming illegal.

If you wish to go illegal and accept full responsibility for your actions, you may obviously choose different region (i think russia has no DFS requirements on any frequency)

Comparison with UBNT doesn't necessary mean anything. If you compare UBNT on 5180 with mikrotik on 5260, then obviously you will see DFS in action on mikrotik but not on UBNT. Often I see people comparing stuff without context and without taking all variables into account.
 
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Re: radar detected problems

Fri May 18, 2018 10:28 am

Comparison with UBNT doesn't necessary mean anything. If you compare UBNT on 5180 with mikrotik on 5260, then obviously you will see DFS in action on mikrotik but not on UBNT. Often I see people comparing stuff without context and without taking all variables into account.
Of course I am not comparing like that!
I am comparing putting up a MikroTik and a Ubiquiti access point at a high tower (see photos of towers) and then seeing the MikroTik chasing all around the channels and never staying on a channel for more than a few minutes before detecting radar again and choosing a different channel (with associated DFS wait), and the Ubiquiti finding radar on maybe a couple of channels but staying on other channels just fine without detecting any radar.
And this is not a MikroTik-specific issue either! In the past I used TranZeo equipment as well, and they sold a couple of different hardware designs all under the same TR5a label, where the first design worked absolutely stable under all firmware releases and the second one on the same location after some firmware release just would not link anymore, only radar detected all the time. And those were not so easy to downgrade....
I think it is a matter of combination of hardware and software. Probably the hardware (the radio) has some detection of pulses that results in some interrupt that is associated with a couple of register values like amplitude and duration of the detected pulse, and the software has to evaluate those, apply decision levels and/or do some filtering (ignore a single pulse but act on repeated pulses), and the quality of that software varies between manufacturers and software releases. Maybe they sometimes tweak the software after having some difficulty getting it type-approved in some country, and when the thresholds were lowered the users suffer.
Quality of the radio front-end could also be part of the issue. When the radar is quite local and causes a large signal on the channel where it is operating, this may overwhelm the receiver and cause detected radar pulses on more than one or even on all available channels. Thus the same software algorithm could still behave differently in different AP designs.
Solving the issue is complicated by the lack of debugging tools and tracing information. If only there would be some table of observed radar events and some of the values the hardware has returned and how the software has acted upon them, it could be possible to research what is going on.

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