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Re: [Discuss-gnuradio] fft realated problems

From: kaleem ahmad
Subject: Re: [Discuss-gnuradio] fft realated problems
Date: Tue, 4 Nov 2008 07:59:09 -0800 (PST)

Dear Firas,

Thanks for your reply, First of all I am using antenna (RX2), and yes I know
2.4 band is messed up with many wireless tech. but I am continuesly
monitoring it with spectrum analyzer during my experiments to make sure that
some other system is not working in the area.

I have tried with many TX and RF gains.

I am also using log function, and I have already checked with larger
tune_delays but all in vain????????

Any suggestions??

Best Regards
Kaleem Ahmad

Firas A. wrote:
> Hi,
> 1) Are you feeding RF2400 directly from signal generator or by Antenna ?.
> Remember that the ISM 2.4GHz band is occupied  by wireless devices.
> 2) Is your RFX2400 works normally with usrp_fft.py ? Can you see clearly
> the signals you generate in it at the specified frequencies ?. Try to
> Adjust the RF gain in usrp_fft to get best signal view. Use this gain
> value in your experiments.
> 3) Tune delay is very important. When you command the usrp RF
> daughterboard to change its frequency, then there is many delays along the
> digitization path (RF synthesizer tuning time, FPGA FIFO filling time, USB
> transferring time...etc). Using enough tune delay time, you  will be sure
> that the samples entering your FFT block are belong to the requested
> center frequency.
> 4) To clearly see the spectrum, you must use the math log function (as
> implemented in usrp_fft.py).
> Regards,
> Firas 

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