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Thread: WiFi spectrum readings :)

  1. #1
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    WiFi spectrum readings :)

    So, I got hold of a wi-spy 2.4i
    The cheapest wi-spy available, tho the hardware would probably cost you just 10%

    Anyway, since I've never seen measurements (couldn't find anything on the forums) from the wifi of asus routers I thought it would be nice to do a little investigation.

    The thing with wi-spys is, that it can't scan all channels at once, so I left every test running for 10minutes since it seemed a quite clear result after 10min.

    Also, I ran the test in a microwave. Why a microwave? well... I thought it would act as a nice Faraday cage since it's quite crowded with wifi here
    Now I did test if any noise would be generated with a router inside, but I couldn't find any difference, only many other AP's where filtered away a lot.

    The firmware is oleg r2249 (from google code)

    First of all, A screenshot from inside the microwave without my WL-500W running:


    WL-500W default settings:


    WL-500W defaults, but with upper channel


    WL-500W defaults, but with lower channel


    WL-500W defaults, but only 20MHz (none channel)


    It's clearly visible the WL-500W generates a lot of noise around channel 6
    But more interesting is that it seems like it doesn't matter how you set things up... it will always use a 40MHz bandwidth

    For the people who can't see it, an smaller shot with lines I drawed:

    Between the red lines is 20MHz, the yellow lines are an extention to 40MHz so that the WL-500W can serve 270Mbits

    What do you think, more tests?
    if anyone has a better idea for test setup let me know

    p.s. not to be negative about oleg firmware & wifi obviously, I haven't seen results from other firmwares. Also it might be a good chance for wifi tweaking

  2. #2

  3. #3
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    Quote Originally Posted by theMIROn View Post
    nice test! thank you
    whats about rt-n models?
    I've only did a quick test on my rt-n16.
    also I should put some load on the AP next time, it's supposed to create a flat line around the central channel

  4. #4

  5. #5
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    Quote Originally Posted by theMIROn View Post
    So, awaiting
    Did some tests on the RT-N16, and found out I really have to put load on it to make the true signal visible

    Yet, for the ppl who like to see the raw values:
    rt-n16 default: http://i52.tinypic.com/2rzuyib.jpg
    rt-n16 upper: http://i55.tinypic.com/2i052jc.jpg
    rt-n16 lower: http://i55.tinypic.com/2mpztpz.jpg
    rt-n16 20mhz: http://i55.tinypic.com/2yukaco.jpg


    Now, I measured the following results by downloading a file from the usb stick

    defaults with load (channel 11, lower 2nd channel):


    lower, surprisingly it shows the higher channel is used.
    central channel is 6:


    higher, surprisingly it shows the lower channel is used.
    central channel is 6:


    20MHz


    for the 20mhz band it looks like it's just adding a secondary 20mhz band on the same frequency range

  6. #6
    Great!
    We've already discussed that choosen channel is the primary (control) channel, and upper/lower options means that exactly primary channel will be upper/lower, but not secondary or central.
    So, I'm thinking about to change SubChannel name to something like Primary, or exchange lower/upper values. But the second will confuse users, am I wrong?

    BTW, can you test official RT-N16 FW 1.0.1.9, there're changes related to wifi power saving.
    They could change 20Mhz freq usage map, I hope.
    Last edited by theMIROn; 13-10-2010 at 21:10.

  7. #7
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    Quote Originally Posted by theMIROn View Post
    Great!
    We've already discussed that choosen channel is the primary (control) channel, and upper/lower options means that exactly primary channel will be upper/lower, but not secondary or central.
    So, I'm thinking about to change SubChannel name to something like Primary, or exchange lower/upper values. But the second will confuse users, am I wrong?

    BTW, can you test official RT-N16 FW 1.0.1.9, there're changes related to wifi power saving.
    They could change 20Mhz freq usage map, I hope.
    hmm... the control channel is the channel showing up on your wifi card right?
    then why does the subchannel shift from the control channel in this picture: http://i55.tinypic.com/2zohhxx.jpg ? that parabolic line is drawn by the same software btw

    Anyway, changing the subchannel name would probably be the easiest thing to understand I guess.

    Maybe I have time to scan the official asus fw tomorrow, I also wonder what graphs dd-wrt produces

  8. #8
    Quote Originally Posted by wpte View Post
    hmm... the control channel is the channel showing up on your wifi card right?
    yep

    Quote Originally Posted by wpte View Post
    then why does the subchannel shift from the control channel in this picture: http://i55.tinypic.com/2zohhxx.jpg ? that parabolic line is drawn by the same software btw
    11 is higher control, 7 is lower sub and 9 is center channel. Whatz wrong?
    http://en.wikipedia.org/wiki/IEEE_80...n_2.4.C2.A0GHz

  9. #9
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    Quote Originally Posted by theMIROn View Post
    11 is higher control, 7 is lower sub and 9 is center channel. Whatz wrong?
    http://en.wikipedia.org/wiki/IEEE_80...n_2.4.C2.A0GHz
    *slaps in his face*
    yes, I was confused

  10. #10
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    I think my WiFi might be broken, got a packet loss of 30% or so

    Time to send it back to let them repair it, good thing I never opened it up
    should be done within 3 workdays, which is in holiday period for me, so after that I can measure it

  11. #11
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    Quote Originally Posted by wpte View Post
    I think my WiFi might be broken, got a packet loss of 30% or so
    Finally, antennas where broken apparently

    Anyway, I tried the original asus firmware, but I couldn't possibly get it into 40MHz mode

    so the only result I got:


    The 20MHz band does look different than from oleg

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