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Re: [Discuss-gnuradio] Re : audio signal transmission

From: Lingeswar Lingeswar
Subject: Re: [Discuss-gnuradio] Re : audio signal transmission
Date: Wed, 14 Nov 2012 15:22:46 +0530

hi guelord, thanks for reply..
the thing is i can able to hear some sound at the reciever similar to the actual signal with some noise using these flow graphs. whereas if i use the modulation scheme i can't able to get even noise at the reciever.
i am using USRPN210 and the daughter board is XCVR2450 and the antenna is VERT2450. i used the wbfm and nbfm techniques and i got the same results as that of the results i got using the grc files which i sent you earlier. the files i used for these fm techniques are attached in the single file(i.e transmitter and receiver are given in one file).

On Wed, Nov 14, 2012 at 12:33 PM, guelord ingala <address@hidden> wrote:
I do believe that these flow graphs will not work.
Transmitter side:
The audio signal (wav file) is not modulated. you simply connected it to the ursp. I'll suggest you to find a modulation scheme for your communication system. You may use WBFM transmit. Your usrp center frequency is 2.5 GHz, it is then assumed that your antenna operates at 2.5 GHz, otherwise you are wrong. So for your transmitter at this stage, I suggest to have: wav file, modulator, and usrp sink. Set usrp sink for complexe float 32. Usrp gain of 50 dB is too high, set it 20-30 dB.
Receiver side:
you need a demodulator. this must match the modulation scheme of the transmitter. you may use WBFM Receive. usrp source gain is too high. 20-30 dB is fine. the audio sink sample rate is 44.1 KHz, but the incoming data has been sampled at 195.312 K. This is a problem. It is called sample rate mismatch. You need to make sure that the incoming data is down-rated (decimated) before reaching the audio sink. You may use the fractional interpolator under filter menu to do it. So your receiver must have: usrp source, demodulator, sample rate adjust, audio sink.

This system is not optimum yet.  But it is a good start.you might still have some problems. Keep me posted if you have trouble. Please tell me which usrp you are using (2, N200 or N210), and which daughter board you've got.

Good luck :)

Durban University of Technology.

--- En date de : Mer 14.11.12, Lingeswar Lingeswar <address@hidden> a écrit :

De: Lingeswar Lingeswar <address@hidden>
Objet: Re: Re : audio signal transmission
À: "guelord ingala" <address@hidden>
Cc: address@hidden
Date: Mercredi 14 novembre 2012, 5h48

Hi guelord, thanks for reply i am attaching the grc files. kindly go through those files and send me the necessary corrections.

On Mon, Nov 12, 2012 at 11:42 AM, guelord ingala <address@hidden> wrote:
Hi Lingeswar,
I guess it would be a good idea if you could send me a picture of your flow graph in order to see components you are using and how you are setting them. please give me any information if possible.

--- En date de : Sam 10.11.12, Lingeswar Lingeswar <address@hidden> a écrit :

De: Lingeswar Lingeswar <address@hidden>
Objet: audio signal transmission
À: address@hidden
Cc: address@hidden
Date: Samedi 10 novembre 2012, 6h01

thanks for your reply. you mean the gain in usrp specifications in the usrp? if so i tried it also but the result is still same. how to know the rate of audio signal received. however i used throttle to manage it at 44100hz. 



Attachment: NBFM_27Aug.grc
Description: Binary data

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