Re: [Discuss-gnuradio] The shortest pulse length

[Eric Blossom]

On Thu, Mar 01, 2007 at 12:15:36PM -0500, David Scaperoth wrote:
> On 3/1/07, seph 004 <address@hidden> wrote:
> >
> > This is what I did:
> >
> >def build_graph ():
> >    nchan = 1
> >    interp = 512
> >    duc0 = 0
> >    duc1 = 0
> >    fs = 250e3                                        #2nd sample rate
> >between usb and dac
> >    max_dev = 32e3                              #1st sample rate divided
> >by 4 (1st = 2nd sample rate)
> >    gain = 16e3
> >    k = 2 * math.pi * max_dev / fs
> >    vec1 = Numeric.arange (0.624, 0.656, 0.0000128)
> >    vsource = gr.vector_source_f(vec1, False)
> >    fmmod = gr.frequency_modulator_fc (k)
> >    amp = gr.multiply_const_cc(gain)
> >
> >    fg = gr.flow_graph ()
> >
> >    u = usrp.sink_c (0, interp, nchan)
> >    tx_subdev_spec = (1, 0) #usrp.pick_tx_subdevice(u)
> >    m = usrp.determine_tx_mux_value(u, tx_subdev_spec)
> >    u.set_mux(m)
> >    subdev = usrp.selected_subdev(u, tx_subdev_spec)
> >    subdev.set_enable(True)
> >
> >    sample_rate = u.dac_freq () / interp
> >    u.set_tx_freq (0, duc0)
> >    u.set_tx_freq (1, duc1)
> >
> 
> Are you trying to use one daughter boards(nchen=1)?   Why did you set duc0 =
> 0?   that means your  frequency will not be set at all.  You do not need to
> do set_tx_freq() twice if you are using one daughter board.  you only need :
> u.set_tx_freq (0, duc0) where duc0 is some frequency.  Also, if you are
> using the basic daughterboards, you need to make sure that you have the
> output connector connect to TXA not TXB (according to your tx_subdev_spec)
> 
> 
> Hope this helped.
> David

Lance, you really want to be using tune, not set_tx_freq.
tune knows about all the daughterboards and does the right thing to
split the work between the digital upconverter and the RF front end (if any).

Take a look at fm_tx4.py or fm_tx_2_daughterboards.py

Eric