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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 19:58:25 +0530

ya i checked the datasheet of vert2450 and i tried at 2.45G not at 2.5G. i just merged two files into one single file. i have two usrp and two daughter boards as well. and XCVR2450 can support both transmission and reception at high and low frequency bands. and i know that it cannot support full duplex transmission. may i know the grc files and the details of your usrp, daughter boards and gnuradio versions you used for audio transmission.. thanks.

On Wed, Nov 14, 2012 at 5:48 PM, guelord ingala <address@hidden> wrote:
I'm a bit confused. For the first files you sent me, the system frequency was 2.5 GHz. Which implies directly that VERT2450 will not work (see data sheet).
but for the second files, the system frequency is 2.4 GHz which works well with the antenna. But ...
In both cases, I'm seeing a problem with XCVR2450 board. It seems to me that this daughter board operates for 2.4 - 4.5 GHz for transmitter only and 4.9 - 5.9 GHz for receiver. if so, then the receiver cannot work for 2.4 or 2.5 GHz. I'm not too sure about it. Please research and find out.
I guess you're having at least 2 separate usprs and 2 XCVR2450 (one for TX and one for RX). If not, then then setup will not work as the XCVR2450 cannot be used for full-duplex application. Hope you've read this link: http://files.ettus.com/uhd_docs/manual/html/dboards.html#xcvr-2450

After all this, my suggestion is to get a daughter board that suits your application easily. i.e SBX board. this will help to operate at single frequency (2.4 GHz) for the TX, your antenna, and the RX.

I did audio transmission at 915 MHz, it was successful.

Keep me posted.


--- 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, 10h52

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. 



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