Today I had to call support to change my WiFi channel, because it was using channel 7, and the guy on the phone told me that channel 1 was "less powerful" than channel 11, and that I should use channel 11.

Using a wifi analyzer app, I found that channel 1 is the least used in my building, so I ignored his recommendation and asked for channel 1.

Was he right? Is channel 11 better?

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    Technically, really nit-picky physics/math technically, channel 11 is broadcasting at a frequency that's a few MHz higher than channel 11. Mathematically, that does mean the electromagnetic waves on that channel have a tiny bit more energy. But difference completely negligible. You did the right thing by picking the one that has the least use. – mtraceur Dec 8 '16 at 6:36
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    @mtraceur see en.wikipedia.org/wiki/Free-space_path_loss – Alnitak Dec 8 '16 at 9:39
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    @mtraceur But also with higher frequency the penetration decreases - so there is that trade off as well. – Philipp Dec 8 '16 at 12:46
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    @mtraceur, just to join the physics nitpick party, transmitting at a higher frequency & keeping same amplitude (voltage) ==> higher power. But 20 dBm (100 mW) @ 2.412 GHz should be the same power (by definition) as 20 dBm (100 mW) @ 2.462 GHz. The 2% higher frequency would be combined 2% lower amplitude to preserve the specified power output to keep the regulators and neighbors happy. I can't say whether consumer WiFi routers do this properly though. – Joshua Huber Dec 8 '16 at 20:20
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    Generally speaking aerials and antennae function most-optimally in the middle of the band that they're designed for. So on that basis channel 6 is the single best channel to use for 2.4 GHz wireless. – Criggie Dec 9 '16 at 7:10

The answer is "sort of" and "it depends".

If you are talking about the 2.4 GHz band - and this would seem to fit your description best - then he is pretty much talking garbage. The best band to be on is the one with the least noise - both on the main frequency and surrounding frequencies. In this case, Channel 1 sounds better and the tech sounds like he does not know what he is talking about.

If you are talking about the 5 GHz band, its a different story. Different channels in the 5 GHz band have different channel widths and different maximum transmission power - thus in the case it may very well be true that (some) higher frequencies do actually have more power. That said, the channel numbers don't match up very well with what you have posted (Channel 1 does not exist, 7 and 11 are generally not legally useable and are low bandwidth anyway)

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Channel numbers do not denote power and so channel 11 is not "better" than channel 1 simply because it is 10 digits higher.

WiFi does have overlapping channels, which means that devices don't want to be on a channel that is too close to another nearby stations channel. For best results and interoperability (least interference) there are only 3 channel choices: channel 1, channel 6 and channel 11. Here is an image showing why: channel overlap

If there are many networks nearby then you want to choose the channel which has the fewest or weakest signals in it. If, as you mention, that happens to be channel 1 then that is the channel you should use.

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    True, for 2.4GHz. That's why you're better off with 5ghz in many instances - many more channels, but different abilities to go through walls. – Rich Homolka Dec 8 '16 at 1:56
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    It's also worth noting that, as a good neighbor, you should (1) avoid using 40 MHz channels as there cannot be more than one in the 2.5 GHz range without overlap and (2) turn down the transmit power as much as possible to cover only the area you need. Ask your neighbors to do the same and you will have a much better Wi-Fi experience. – Jens Ehrich Dec 8 '16 at 14:19
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    @JensEhrich You have neighbors who understand WiFi and actively manage their networks? I want to live where you live. – Sneftel Dec 8 '16 at 14:50
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    @Sneftel Not exactly, but I'm starting to. I spoke to many of my neighbors, and also created an open 'Free Internet' SSID that first redirects people to a page with some Wi-Fi pointers like this one. About 6-8 months later I had only a very small number of (weak) overlapping networks (note that I can see 70-90 APs from my location, with 30+ active at any given time). – Jens Ehrich Dec 8 '16 at 14:57
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    @MarkRansom it has to do with regulations. AFAIK it is only allowed in Japan, so wireless APs sold in US & EU market only allow for the 1-13 range. Clients should be able to connect to APs on channel 14, even outside of Japan, or when an US client is placed in there. – beppe9000 Dec 8 '16 at 16:43

Given the same transmitter output power, in the absence of ANY interference, the lowest-frequency channel will nearly always be the best. This is because higher-frequency radio waves do not penetrate matter (including air) as well as lower-frequency waves.

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  • This answer is meaningless - there is no such thing as the absence of ANY interference in any remotely plausible scenario. Similarly, higher frequencies will have more transitions, so assuming a reality where there is any noise at all, higher frequencies will be able to transmit more data in the same timeframe. – davidgo Dec 17 '16 at 2:37
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    The question pertained to the 2.4 GHz (and, by extension, the 5GHz) bands. The user bandwidth at those frequencies is not frequency-dependent.When I said "in the absence of any interference," I meant to exclude consideration of activity on other channels. The physics of radio-frequency propagation is undeniable. – Steve92169 Dec 17 '16 at 7:36

It is actually probably true that channel 7 is the most powerful channel. The hardware amplifiers and filters in WiFi equipment probably use something around 2.447GHz as their center frequency. Depending on filter design (bandwidth, filter type etc) and other characteristics you could probably see quite a bit (3dB?) of power loss at the outer channels. Will you be able to notice this much roll off? Probably not for innumerable reasons like noise floor and reflections.

Technically amplifiers get slightly less efficient (powerful as they increase in frequency so 1 should be more powerful than 11 if the center frequency is exactly between them, but this is almost certainly in the noise.

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While the answer is no, the trick could be to use Channel 1 or Channel 11 (or last one). In total there are three channels. When you use Channel 1, you are affected only with routers with channels 1, 2 and 3. If you use Channel 6, you are affected with routers with channels 4,5,6,7 and 8.

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    That is assuming that the channels are uniformly populated, that they are not. Analysing the spectrum at your location, as the OP did, is the right way. – Davidmh Dec 8 '16 at 13:06
  • Channel 1 partially overlaps with channels 4 and 5 as well. See the diagram in the accepted answer. – Peter Cordes Dec 8 '16 at 15:14
  • @esQmo: my mistake, the most-upvoted answer doesn't have a check-mark (yet). It's also the only one with a diagram. – Peter Cordes Dec 9 '16 at 14:58

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