Re: [Discuss-gnuradio] Can I do this?

[Ilia Mirkin]

You simply can't do that. The hardware on the USRP has a DAC capable of
128MS/s (iirc), which means that AT MOST you could get it to put out a
64 MHz signal. If you shift over by 98.7MHz, then that'll be past the
DAC's ability to reproduce an accurate signal (it will in fact fold over
to like 98.7 - 64 MHz, I think). Coincidentally, the -c option usually
takes Hz, not MHz, so you're shifting it over by 98.7Hz. (Didn't look at
the actual code, so I could be wrong on that.)

If you want to transmit in the FM band, you will need an upconverter
that will take the baseband signal out of the USRP and move it over to a
higher frequency.

Good luck.

On Tue, 2005-09-27 at 19:19 -0500, Jorge Chávez wrote:
> Hi gnuradio's
> 
> I'm trying to FM TX, can I do this with the fm_tx4.py:
> 
> address@hidden:/home/gr-build/gnuradio-examples/python/usrp # ./fm_tx4.py
> -c 98.7
>  
> When I run it I get this:
> 
> address@hidden:/home/gr-build/gnuradio-examples/python/usrp # ./fm_tx4.py
> -c 98.7 ddc_freq = 98.7
> len(interp_taps) = 356
> >>> gr_fir_fff: using SSE
> len(interp_taps) = 356
> len(interp_taps) = 356
> len(interp_taps) = 356
> TX d'board A: Basic Tx
> TX d'board B: <none>
> 
> But I can't hear in a Radio (98.7MHz) what I record in audio-0(-4).dat
> 
> What am I doing wrong?
> what is missing?
> I'm thinking that it yust work for 29.326MHz, but my convencional
> radio system is not alowed to do this frecuency.
> 
> Thanks for your answers, and sorry for my english..
> 
> Jorge Chávez
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