Re: [Discuss-gnuradio] Need some answers about FM TX

[Jorge Chávez]

Thank you all for your comments.

I try to know in which other frecuancies can I TX when run the fm_tx4.py in my USRP with the BASIC TX, that because I´ve no access to a spectrum analyzer, and would be greate if you can help me with this.

And I want to know the default sample-rate in the fm_tx4.py file.

 

Thanks

 

Jorge Chávez 

On 10/2/05, Matt Ettus <address@hidden> wrote:

Robert McGwier wrote:
> Thanks for all the comments but I still have my doubts.  I am more like
> to believe in clock leakage and DAC nonlinearities causing this than I
> am with square wave harmonic activity.  I will investigate further with
> the spec-an if I have time.
>

When the aliasing happens with an ADC it can be though of as an impulse
train (impulses at the sampling points) being multiplied by the signal.
This is the same as convolution in the frequency domain, resulting in
the aliasing behavior.

With a DAC, it is not a pulse train, but a zero-order hold (aka boxcar
filter, sinc, etc).  Thus the aliases (more properly, alternate images)
are weighted by a sinc function, causing them to get weaker as they get
to higher Nyquist zones.  It is about 18 dB down in the second zone, for
example.

Matt




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