Re: [Discuss-gnuradio] Transmit Frequency

[Eric Blossom]

On Sat, Nov 18, 2006 at 06:27:23PM -0500, Jonathan Shan wrote:
> Hello all,
> 
> sink = usrp.sink_c(0, 64).
> 
> I am confused about the function sink.set_tx_freq(0, 5e6).
> What does this do? I already know the receiver must be set to listen at 
> 5e6 Hz. But what does the function do to my signal?
> 

set_tx_freq controls _only_ the digital upconverter (which happens to
be implemented in the AD9862.)

In general, you want to use

  u.tune(self.subdev._which, self.subdev, target_freq)

which controls both the PLL in the associated RF daughterboard _and_
the digital upconverter.

See gnuradio-examples/python/digital/{transmit,receive}_path.py for
the recommended way to handle the d'board subdev selection and
tuning.  There's addition code in their for picking the appropriate
values of interp and decim, but you can ignore that for now.

Eric