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Re: [Discuss-gnuradio] USRP2 FM TX and FM RX working together

From: Jorge Miguel
Subject: Re: [Discuss-gnuradio] USRP2 FM TX and FM RX working together
Date: Wed, 22 Sep 2010 13:10:40 +0200

I forgot to mention, but I get a lot of messages like:

I did the calculations and with the 104 interpolation USRP sink and 208 decimation USRP source and 16 bits per sample means that less than 100Mbs are taken from the 1Gbps ethernet wire. So there souldn't be any overload.

Furthermore I still don't know why is necessary the multiply cont block in the modulator.

Can anybody help me? I am very close !



On 21 September 2010 18:59, Rafael Diniz <address@hidden> wrote:
Hi Jorge,
Can you copy the .grc file you created?

> Hello community!
> I initiated myself in GNU radio two weeks ago and I am learning as fast as
> I
> can. To begin with, I decided to play with GRC and my URSP2.
> I successfully built a FM modulator that works fine.
> I successfully built a FM demodulator that works fine.
> But there are still several things I do not understand.
> While building the FM modulator:
> 1)Wave file source
> 2)Rational resampler
> 3)LPF
> 4)Rational resampler
> 5)Frequency Mod
> 6)Multiply const
> 7)USRP2 sink
> Why is block 6 necessary? I tried with lots of values over 2 and all of
> them
> are ok. I realized that the smaller the number, the higher the noise in my
> receiver (my mobile phone). Is it related to the amplitude of the
> modulated
> signal?
> Another thing very strange is that if I create a GRC file with both,
> transmitter and receiver with exactly the same blocks and the same
> parameters I cannot hear any demodulated signal. I can see information
> with
> a FFT block connected to the receiver chain, and I am able to demodulate
> the
> signal with my mobile phone when the example is running but in my computer
> I
> do not hear anything else besides noise mixed with some sort of
> non-understandable signal. Thus, I guess I have to change something in the
> receiver chain although it works alone in my FM demodulator. I changed
> every
> single parameter but I cannot get any improvement.
> Any suggestions?
> Many thanks in advance,
> Jorge.

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