Re: [Discuss-gnuradio] I couldn't observe 2.4G Wi-Fi signal and didn't know why

[Tom Rondeau]

On Sun, Nov 10, 2013 at 12:03 PM, Martin Braun (CEL)
<address@hidden> wrote:
> On Sun, Nov 10, 2013 at 11:53:41AM +0800, Howard He wrote:
>> I use four antennas for test. Two are official VERT2400, others are 2.4G
>> antennas. I use the given example "uhd_fft.grc" (a simple FFT block) hoping 
>> to
>> observe frequency spectrum of Wi-Fi signal. No matter what antenna I set up
>> (even without antenna) and what central frequency I tune,  the FFT window 
>> only
>> shows something like noise around -50--60dB on whole spectrum (sample 
>> rate=25M)
>> which is unlike the 802.11 standard.
>>
>> There is low possibility of bad hardware I guess. I doubt that there may be
>> some problems with my test methods and hope for some advice.
>
> Hi Howard,
>
> have you made sure the wifi stations are actually transmitting? Do you
> have a real spectrum analyzer which shows energy transmitted?
> And are you on the correct centre frequency?
>
> MB

Also remember that Wifi is bursty and can be fairly low power. You
won't see it constantly and will only see bursts of energy. If you do
a peak/max hold you'll start seeing something and a
spectrogram/waterfall plot will show you the the signal bursts.

Tom