Re: [Discuss-gnuradio] gr-usrp library

[Ges]

Thanks Eric. 

I looked up the max gain. It is 20dB. So I set it to 20 dB on the tx and rx side. Also I was using payload size of 1024; so I tried different sizes 512, 256 and 64. The size of the file was 1087 bytes.  But it doesnt seem to have any difference. I even tried a different frequency - 100MHz. Looks like I will have try the gmsk2 blocks and see what I am getting. Unless I am going wrong with something else! 

Thanks,
Gesly



Eric Blossom <address@hidden> wrote:
>  On Sun, Apr 09, 2006 at 01:55:33PM -0700, Ges wrote:
> > Hi Eric,
> > 
>
> > I tried using the gnuradio blocks in gmsk (the old python script :
> > gmsk-test.py) and sending a file across from one usrp (using the
> > basic daughter cards) to the other using SMA cable - the same
> > connection setup I had mentioned
>  earlier.
> > 
> > I am simply modulating a char stream using the blocks in
> > gmsk-test.py and sending it out using usrp_sink and using
> > usrp_source to receive and then demodualting using the blocks in
> > gmsk-test.py and dumping to a file.
>
> Have you tried plotting the raw received signal using usrp_oscope?
> Does the signal look OK?
>
> > I am not sure what is happening, but the general_work() of the
> > simple_correlator() simply returns 'zero'. And hence I have no
> > output in the file_sink(). I have set a tx freq of 29.32e6 and a rx
> > freq of the same value. I had tried with a gain of 0 on both sides n
> > then with a gain of 20. But the results seem to be the same....
>
> The transmit and receive gain setting have different allowable ranges.
> Try setting them both to their maximum value.  You can query any usrp
> daughterboard for its allowable range of gains.   Many of the examples
> to this.  grep for
>  gain_range.
>
>
> From db_base.py, the abstract base class for all daughterboards:
>
>     def gain_range(self):
>         """
>         Return range of gain that can be set by this d'board.
>
>         @returns (min_gain, max_gain, step_size)
>         Where gains are expressed in decibels (your mileage may vary)
>         """
>         raise NotImplementedError
>
>     def set_gain(self, gain):
>         """
>         Set the gain.
>
>         @param gain:  gain in decibels
>         @returns True/False
>         """
>         raise NotImplementedError
>
>
>
> > Is it because of the simple_correlator() or is somehting else
> > possibly going wrong? Please help....
>
> simple_correlator works reasonably well for blocks of data that are
> up to a couple of hundred bytes long.  This assumes that you're feeding
> it 8x oversampled data, etc.
>
> > I will be trying out the new blocks in the gmsk2 implementation. I
> >
>  did not want to do a CVS update due to some other issues. I guess I
> > will grab those blocks and recompile gnuradio-core.
>
> Good idea.  They are known to work with the Flex 400 cards.
>
> > Thanks a lot
>
> You're welcome.
>
> Eric

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