How do you deal deal with DFS channels?

Firegod

Firegod

Firegod

Soldato
Joined
12 Sep 2003
Posts
10,514
Location
Newcastle, UK
Hi everyone.

Lately been having a battle with DFS channels in my setup. x2 APs either end of the property (single story bungalow). One side of the property has a neighbour. They (for some reason) appear to have 2 devices (potentially a router and a sky booster) both using 80Mhz wide channels on 5Ghz. Urgh. So the AP down that side of the property I have set to use a DFS channel. I've tried a few low DFS channels to escape the neighbours coverage (example below) and also a higher random one (100).

Radar.jpg


I've been thinking we're not exactly near anything so what could be around me...

1. I did some searching and found this weather station in the area (about 10 miles away) which apparently has coverage up to 150 miles! I'm guessing this could be the likely culprit?
2. Other things are Newcastle airport which is 12 miles away.
3. And apparently looking at some Ofcom information we have two military radars in the region but they appear to be about 40 miles away from me.

I was wondering what frequency range (or channel) could potentially avoid the weather station in particular? Or is it a case of just try them all? I am still on channel 60 monitoring the logs, but if it happens again I was going to go far end, and select channel 140 (I can't go higher than this).

Also, I was wondering for advice... I've dropped my channel width to 40Mhz from 80Mhz. Can I ask, if as above, the Radar signal is detected on channel 60 when I was using an 80Mhz slice, since dropping to 40Mhz, could that potentially have helped (I'm thinking less overlap now)? I've not seen an occurance in the logs again. So I was just curious if that could have helped.

I am going to speak with my neighbour, see if he can't either reduce down to 40Mhz or potentially remove one of the devices if unneeded. That would be a real help here.

Curious to see how others get on with DFS channels or do you try and avoid them? :)

Thanks
 
Firegod said:
Hi everyone.

Lately been having a battle with DFS channels in my setup. x2 APs either end of the property (single story bungalow). One side of the property has a neighbour. They (for some reason) appear to have 2 devices (potentially a router and a sky booster) both using 80Mhz wide channels on 5Ghz. Urgh. So the AP down that side of the property I have set to use a DFS channel. I've tried a few low DFS channels to escape the neighbours coverage (example below) and also a higher random one (100).

Radar.jpg


I've been thinking we're not exactly near anything so what could be around me...

1. I did some searching and found this weather station in the area (about 10 miles away) which apparently has coverage up to 150 miles! I'm guessing this could be the likely culprit?
2. Other things are Newcastle airport which is 12 miles away.
3. And apparently looking at some Ofcom information we have two military radars in the region but they appear to be about 40 miles away from me.

I was wondering what frequency range (or channel) could potentially avoid the weather station in particular? Or is it a case of just try them all? I am still on channel 60 monitoring the logs, but if it happens again I was going to go far end, and select channel 140 (I can't go higher than this).

Also, I was wondering for advice... I've dropped my channel width to 40Mhz from 80Mhz. Can I ask, if as above, the Radar signal is detected on channel 60 when I was using an 80Mhz slice, since dropping to 40Mhz, could that potentially have helped (I'm thinking less overlap now)? I've not seen an occurance in the logs again. So I was just curious if that could have helped.

I am going to speak with my neighbour, see if he can't either reduce down to 40Mhz or potentially remove one of the devices if unneeded. That would be a real help here.

Curious to see how others get on with DFS channels or do you try and avoid them? :)

Thanks
Click to expand...
How dare you neighbour use 80Mhz width.
I'm using channel 149 for my 5ghz nothing else even close from my neighbours so nice and clear for my use.
 
robj20 said:
How dare you neighbour use 80Mhz width.
I'm using channel 149 for my 5ghz nothing else even close from my neighbours so nice and clear for my use.
Click to expand...
I know right. :cry: It's a shame I can't select anything past 140 as you say, something in the 149, 153, 157, 161 and 165 would be a quick fix.

I forgot to mention in the first post, there's not really an issue with the DFS channel and how the AP handles the detection, the clients are moved and the AP will then change back to the set channel after a set time. But it's more that we use WiFi calling and so having the potential for choppy audio or drops isn't ideal (if using that AP at the end of the property).
 
I don’t like the DFS channels. In the UK they flake out far too often and a properly legitimate firmware will shut that channel down if it detects radar. And that’s no good to man or beast. You want stability. If you chat to your neighbour there is plenty of non-DFS bandwidth to share, even at 160MHz channel width.
 
I find it's very location dependant. For my home area, DFS 52-64 is completely fine to use, I haven't noticed any issues with gaming over wireless even with local stream from PC/PS5 to Steam Deck. 100-144 is unusable due to more radar events. Non-DFS 149+ is clear but for some weird reason, not all my devices can see these channels.

At work in central London, all DFS channels are pretty much unstable.
 
I'm having some success on the highest channel I can select - ch136 with a 40Mhz slice. So far over the last 2 days, I've not seen any repeat of the Radar activity in the logs. So hopefully this will continue. I am looking into replacing the APs with a proper tri-band model to offer more flexibility. :)
 
Is it possible to lock out the router from switching away from DFS channels?

I dont really understand why DFS channels switch away. 5GHz wifi only has a range of maybe 50m max, so if I am say 10 miles from something, why should their use of a DFS channel be in range where I am?

And why does wifi analyser not show something on the DFS channels? Its showing those channels are clear for me, yet Im having problems holding on to them when I switch to them.
 
danlightbulb said:
Is it possible to lock out the router from switching away from DFS channels?

I dont really understand why DFS channels switch away. 5GHz wifi only has a range of maybe 50m max, so if I am say 10 miles from something, why should their use of a DFS channel be in range where I am?

And why does wifi analyser not show something on the DFS channels? Its showing those channels are clear for me, yet Im having problems holding on to them when I switch to them.
Click to expand...
Because other things that uses those DFS channels aren't WiFi networks (eg radar), so phones/apps won't understand what's broadcasting on that channel. They also have much higher power limits, which ends up giving them a much bigger range. You need more specialised equipment (eg spectrum analyser) to see those sort of things.

Interesting note, microwaves uses 2.4GHz, and I have seen cases where leaky microwaves can affect WiFi. A friend was confused why their WiFi sometimes stopped working, after a few weeks we nailed the cut-outs matched when the microwave was on. Replaced the microwave and issue was fixed. Of course, this didn't appear on WiFi analyser apps.
 
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danlightbulb said:
Ok, makes sense, but the range of MY wifi would only be max 50m. So why does it matter if Im on the same DFS channel as something locally with much higher power? I won't have the power to interfere with their signal.
Click to expand...
In case you're in-between what's broadcasting it and what's receiving it. Your network will basically be interfering with it.
 
danlightbulb said:
Is it possible to lock out the router from switching away from DFS channels?
Click to expand...

No. All use of radio frequency equipment in the UK is strictly licensed and the use of the upper (in WiFi terms) 5GHz band is reliant on the device switching away from from that channel if it detects radar.

danlightbulb said:
I dont really understand why DFS channels switch away. 5GHz wifi only has a range of maybe 50m max, so if I am say 10 miles from something, why should their use of a DFS channel be in range where I am?
Click to expand...

Because you might not be 10 miles from a police radar. Let’s say they set up a speed camera operation outside your home and switched it in and you were interfering with it, it wouldn’t help either party. So your WiFi switches back to a non-DFS channel and everything works. I had a fun diagnostic session with some lovely pensioners whose WiFi would die at apparently random times. It just happened to co-incide with them being on the flight path of an AWACs aircraft landing at Lakenheath or Mildenhall. Switching away from DFS sorted that out immediately.

danlightbulb said:
And why does wifi analyser not show something on the DFS channels? Its showing those channels are clear for me, yet Im having problems holding on to them when I switch to them.
Click to expand...

Because it’s a WiFi analyser, not a spectrum analyser. It’s only looking for SSIDs (and hidden ones). It’s not even looking for ‘normal’ stuff like TV remotes, cheap wireless CCTV, microwave ovens etc. Never mind radars.
 
You would think that the 'professional' services like airports, police etc, could have a spectrum of their own, rather than having to overlap with domestic wifi channels. The current number of non-dfs channels is not sufficient when you're in close proximity with neighbours.
 
danlightbulb said:
You would think that the 'professional' services like airports, police etc, could have a spectrum of their own, rather than having to overlap with domestic wifi channels. The current number of non-dfs channels is not sufficient when you're in close proximity with neighbours.
Click to expand...

They used to then WiFi came along to share some of it. There are plenty of available channels except no-one talks to their neighbours anymore.
 
WJA96 said:
They used to then WiFi came along to share some of it. There are plenty of available channels except no-one talks to their neighbours anymore.
Click to expand...

Is that the case? I thought 80 MHz used half of the non DFS channels and 160 MHz uses all of the non DFS channels. If that's correct (it may not be) then you'd only fit 2 standard 80MHz networks within the local range.
 
danlightbulb said:
Is that the case? I thought 80 MHz used half of the non DFS channels and 160 MHz uses all of the non DFS channels. If that's correct (it may not be) then you'd only fit 2 standard 80MHz networks within the local range.
Click to expand...
How can 160 use all of it when it's split in half, isn't it? I have a 80mhz channel below and above the DFS channels.
 
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