Re: [Discuss-gnuradio] Question about setting transmited signal power

[Vincenzo Pellegrini]

Hi,
I've got a similar problem, I've been searching the online documentation
at http://www.gnu.org/software/gnuradio/doc/ for info about the
set_pga(), but couldn't find anything, because the usrp sources and
sinks don't seem to be documented there.
The programmable gain amplifier immediately follows the dac and is
directly built onto the the motherboard, right?

Can anybody point me to some info source about the set_pga() member
and/or, more generally, about the usrp source/sink blocks?

thanks 
merry Xmas to everybody 

vincenzo

On Wed, 2006-12-20 at 22:14 +0800, hanwen wrote:
> Hi,
>  
> I've got some pieces of flex2400 in the lab, one of which runs
> usrp_oscope.py at 2.45GHz for monitoring the signal power. We change
> different flex2400 on another motherboard to see the difference of
> their power. Surprisingly, with the same transmitter program, and the
> same location of TX & RX antennas, the signal power received differs a
> lot from board to board. Some with amplitude of 1~2 hundred, some
> several thousand.
>  
> Is there anything I missed when setting transmitting power in the
> script? The following is the code setting the usrp_sink:
>  
>         u = usrp.sink_c (0, self.usrp_interp)
>         subdev_spec = usrp.pick_tx_subdevice(u)
>         print "subdev_spec = ", subdev_spec
>         mux_val = usrp.determine_tx_mux_value(u, subdev_spec) 
>         print "mux_val = 0x%x" % mux_val
>         u.set_mux(mux_val)
>         subdev = usrp.selected_subdev(u, subdev_spec)
>         u.set_pga (0, options.gain)
>         u.set_pga (1, options.gain)
>         subdev.set_gain(subdev.gain_range()[1])
>         subdev.set_auto_tr(True)
>         r = u.tune(subdev._which, subdev, freq)
>  
> It seems the set_pga() has no effect on transmitting power. Why?
> The return value of subdev.gain_range() is [0, 0, 1], I don't know
> what it mean, and still, it seems there is no differnce whether I set
> the gain of daughterborad to 0 or 1.
>  
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