5ghz channel and 20/40/80mhz ?

beachBOYken

beachBOYken

beachBOYken

Soldato
Joined
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Posts
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Location
London
Hi

Im currently using channel 44 on 5ghz band which gives me 80mhz channel width.

Within my router I have auto 20/40/80mhz.

I was going to try a higher channel such as 136 or 140 but I noticed channel 136 used 40mhz and 140 used 20mhz.

Is there any disadvantage to using 20/40mhz?

I dont really understand all this much, so hopefully someone can explain. Would I be best just sticking to channel 44.

Thanks
 
Rolls up sleeves
There are multiple channels in the 5Ghz spectrum. Some are usable and some are usable under certain conditions.

Without going "all numbers" on you;
Band A (lower) is the indoor part, lower end channels 36-48 (5180-5240), max transmit power of 200mw (23dB eirp)
Band A (middle) is a meh which you probably don't need to know about / use channels 52-64 (5260-5280) which is indoors with DFS
Band B is the indoor/outdoor where by you MUST use DFS regardless if you are indoors or out channels 100-140 (5500-5700), max transmit power of 1W (30dB eirp)
Band C is outdoor and designed for PtP and you should be using an OFCOM license for, channels 149-161 with a max transmit power of 4W (36dB eirp)
Point to note ^^ Band C has just had some changes where there are now 6 usable channels not 4 but I don't have the channel numbers to hand but regardless you shouldn't really be using them.

So...
Stick with band A for home use, it's indoors and believe me power really isn't everything although the uneducated will often argue this.
There are 4 20Mhz channels in band A, 36, 40, 44 and 48.
If you use a 40Mhz channel width then there are 2 channels available (2x20Mhz's make your 40Mhz)
As you'd expect 4x20Mhz channels would give a total of 80Mhz width which is where your 80Mhz channel comes from.

The channel "number" in this instance is more dependant on your kit, for 40Mhz some use Ce (Channel & Extension) and some uses eC (Extension & Channel).
80Mhz gives more variation of this, your channel 44 with 80Mhz consists of eeCe (Extension, Extension, Channel, Extension) if we are operating in the previously mentioned Band A.

The wider the channel the faster it will go however the density of your power decreases by 3dB as you double your channel width (20>40>80).
Imagine it's like using one of those small pots of jam on 1 slice of bread, 2 slices or 4 slices. The jam is your power (23dB) and the slices are your channel widths (each at 20Mhz). 1 slice the jam is very concentrated, double the amount of slices and you half the amount of jam per slice and then halved again when you double the slices again. Easy way to remember is +3dB is a double in power and -3dB is a half in power. Bear in mind though the power from your router is not reduced at this, you are just spreading the power more thinly across the spectrum.

TL;DR
Stick with 80Mhz on channel 44 as some devices may support it and most routers will drop down to 40Mhz to cater for non compliant devices. On my access networks I operate 2.4Ghz on 20Mhz width and 5Ghz on a 40Mhz width as not enough 5Ghz stuff supports 80Mhz yet and you just increase the collision zone.

Otherwise make sure your router is set to UK locality with an up to date firmware and trust it will operate legally for you and within the parameters set by OFCOM.

Your address says London which from my "small town" mentality makes me think of densely packed areas with lots of local noise so you'd be better operating on slimmer channels and actually reducing power if you can to reduce the noise floor to get better signal to noise.
 
Steveocee said:
Rolls up sleeves
There are multiple channels in the 5Ghz spectrum. Some are usable and some are usable under certain conditions.

Without going "all numbers" on you;
Band A (lower) is the indoor part, lower end channels 36-48 (5180-5240), max transmit power of 200mw (23dB eirp)
Band A (middle) is a meh which you probably don't need to know about / use channels 52-64 (5260-5280) which is indoors with DFS
Band B is the indoor/outdoor where by you MUST use DFS regardless if you are indoors or out channels 100-140 (5500-5700), max transmit power of 1W (30dB eirp)
Band C is outdoor and designed for PtP and you should be using an OFCOM license for, channels 149-161 with a max transmit power of 4W (36dB eirp)
Point to note ^^ Band C has just had some changes where there are now 6 usable channels not 4 but I don't have the channel numbers to hand but regardless you shouldn't really be using them.

So...
Stick with band A for home use, it's indoors and believe me power really isn't everything although the uneducated will often argue this.
There are 4 20Mhz channels in band A, 36, 40, 44 and 48.
If you use a 40Mhz channel width then there are 2 channels available (2x20Mhz's make your 40Mhz)
As you'd expect 4x20Mhz channels would give a total of 80Mhz width which is where your 80Mhz channel comes from.

The channel "number" in this instance is more dependant on your kit, for 40Mhz some use Ce (Channel & Extension) and some uses eC (Extension & Channel).
80Mhz gives more variation of this, your channel 44 with 80Mhz consists of eeCe (Extension, Extension, Channel, Extension) if we are operating in the previously mentioned Band A.

The wider the channel the faster it will go however the density of your power decreases by 3dB as you double your channel width (20>40>80).
Imagine it's like using one of those small pots of jam on 1 slice of bread, 2 slices or 4 slices. The jam is your power (23dB) and the slices are your channel widths (each at 20Mhz). 1 slice the jam is very concentrated, double the amount of slices and you half the amount of jam per slice and then halved again when you double the slices again. Easy way to remember is +3dB is a double in power and -3dB is a half in power. Bear in mind though the power from your router is not reduced at this, you are just spreading the power more thinly across the spectrum.

TL;DR
Stick with 80Mhz on channel 44 as some devices may support it and most routers will drop down to 40Mhz to cater for non compliant devices. On my access networks I operate 2.4Ghz on 20Mhz width and 5Ghz on a 40Mhz width as not enough 5Ghz stuff supports 80Mhz yet and you just increase the collision zone.

Otherwise make sure your router is set to UK locality with an up to date firmware and trust it will operate legally for you and within the parameters set by OFCOM.

Your address says London which from my "small town" mentality makes me think of densely packed areas with lots of local noise so you'd be better operating on slimmer channels and actually reducing power if you can to reduce the noise floor to get better signal to noise.
Click to expand...

Thanks very much for the explaination, much appreciated!
 
Steveocee said:
TL;DR
Stick with 80Mhz on channel 44 as some devices may support it and most routers will drop down to 40Mhz to cater for non compliant devices. On my access networks I operate 2.4Ghz on 20Mhz width and 5Ghz on a 40Mhz width as not enough 5Ghz stuff supports 80Mhz yet and you just increase the collision zone.

Otherwise make sure your router is set to UK locality with an up to date firmware and trust it will operate legally for you and within the parameters set by OFCOM.

Your address says London which from my "small town" mentality makes me think of densely packed areas with lots of local noise so you'd be better operating on slimmer channels and actually reducing power if you can to reduce the noise floor to get better signal to noise.
Click to expand...

When you say slimmer channels, do you mean by that use a channel that operates on 20 or 40mhz. When I last looked in my router settings channel 136 gave me 40mhz and channel 140 gave me 20mhz. (not sure if it makes a difference but i like to keep the Mhz setting on 20/40/80 auto).
I did check Inssider and I only had one other 5ghz channel showing which was on 157.
 
beachBOYken said:
When you say slimmer channels, do you mean by that use a channel that operates on 20 or 40mhz. When I last looked in my router settings channel 136 gave me 40mhz and channel 140 gave me 20mhz. (not sure if it makes a difference but i like to keep the Mhz setting on 20/40/80 auto).
I did check Inssider and I only had one other 5ghz channel showing which was on 157.
Click to expand...

If you are only seeing other 5Ghz on 157 then try to go to the "bottom" end and aim for 36 or 40. There is no harm leaving the 5Ghz on 20/40/80 as your devices ultimately dictate what they will use. If they can use 80Mhz width then they will but most probably won't and will default back to 40Mhz.
 
Steveocee said:
If you are only seeing other 5Ghz on 157 then try to go to the "bottom" end and aim for 36 or 40. There is no harm leaving the 5Ghz on 20/40/80 as your devices ultimately dictate what they will use. If they can use 80Mhz width then they will but most probably won't and will default back to 40Mhz.
Click to expand...

Gotcha, I will leave on 44 then and see how it goes. Thanks:)
 
beachBOYken said:
Thanks, I do wonder why so many people like to use the higher channels and based on your information it doesn't seem necessary.
Click to expand...

I had posted a link to some image on the web but it wasn't actually as correct as I wanted it to be so changed my mind.
People choose the higher channels as in theory you can run more power and there is less up there using it. Reality is though that as much as you turn the power up on your router, your device will still only receive at the same level and transmit at the same level so it's needless. Like having a conversation with someone and walking away from each other whilst 1 shouts louder and the other continues at the "normal" level.

Higher end channels are better used with appropriate gain antennas to make fixed wireless point to point or point to multi point networks. I'm trying to find something online to give you an image of channels etc but am resorting to maybe having to make one (busy day at work).
 
Steveocee said:
I had posted a link to some image on the web but it wasn't actually as correct as I wanted it to be so changed my mind.
People choose the higher channels as in theory you can run more power and there is less up there using it. Reality is though that as much as you turn the power up on your router, your device will still only receive at the same level and transmit at the same level so it's needless. Like having a conversation with someone and walking away from each other whilst 1 shouts louder and the other continues at the "normal" level.

Higher end channels are better used with appropriate gain antennas to make fixed wireless point to point or point to multi point networks. I'm trying to find something online to give you an image of channels etc but am resorting to maybe having to make one (busy day at work).
Click to expand...

No worries pal, I got my head around it, thanks for all your help.
 
@Steveocee

Thread resurrection, I have an issue with my Asus AC86U where it will randomly drop the 5ghz wifi, I have tried lots of things to rectify it without success, I was looking on SNB forums and see that the Asus routers can be a bit flakey with wifi and that dropping the bandwidth down to 40mhz has solved it for some people.

Anyway to the point, I have been using channel 40 on 20/40/80mhz following your feedback, I have tried switching to channel 40 with 40mhz but some of my newer devices are failing to connect, maybe that is not a valid setting with channel 40?

May I ask what channel you use with your 40mhz bandwidth setting.

Thanks
 
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